SCHEME OF WORK
WEEK TOPIC
1 Acids: properties, preparation and uses. pH scale
2-3 Bases - properties, preparation and uses
Salts - classification, methods of preparation, types and characteristics i.e. deliquescence, efflorescence, hygroscopic.
4 Carbon - allotropes and their structures, properties, differences between diamond and graphite
5 Carbon (II) oxide CO, carbon (IV) oxide CO2 - their preparations, properties and uses
6 Coal. Types of coal, destructive distillation of coal, uses of the products, coke, gasification and uses
7 a. Metallic carbohydrates: occurrence, preparation and uses
b. Trioxocarbonate (iv) acid: preparation, properties and uses
c. Test for carbonate ion
8-9 a. Introduction to hydrocarbons.
i. Sources of hydrocarbons
ii. Classification of aliphatic hydrocarbons
b. Petroleum and natural gases
i. Refining of petroleum by fractional distillation
ii. Uses of different fractions
iii. Cracking of petroleum ( thermal and catalytic)
iv. Knocking and octane rating
10 Applied chemistry. Raw materials used in chemical industries and their sources
Division of the chemical industries. Heavy and fine chemicals, fertilizers, plastics, metallurgy, pharmaceutical, glass, ceramics, paints, cements, soap and detergent.
11-12 Revision
NEW
TOPIC WEEK
1. Revision of last term’s work
2. Acids, Bases and Salts.
3. Acids, Bases and Salts.
4. Acids Bases and Salts.
5. Water.
6. Carbon and Its Compounds.
7. Carbon and its Compounds.
8. Carbon and its Compounds.
9. Carbon and its Compounds.
10. Revision
11. Examination.
REFERENCE TEXTS
1. Revised 2nd edition Comprehensive Certificate Chemistry by G.N.C Ohia, et al
2. Revised edition understanding chemistry for schools and colleges by Godwin O. Ojokuku.
3. New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio.
4. Melrose Chemistry for Senior Secondary Schools 1 by O. Magbagbeola, et al.
3RD TERM
WEEK 1
TOPIC: ACIDS, BASES AND SALTS
CONTENTS:
(1) ACIDS
i. Definition of acids
ii. Characteristics of acids
iii. Preparation of acids
iv. Reactions of acids
v. Uses of acids
Sub-topic1: ACIDS
Acids are associated with the sour taste we feel when we take fruits such as lemon, lime and oranges especially when they are not ripe. Palm wine left open in the air becomes sour because of the formation of an acid.
(i) Definition of acids: An acid is a substance which produces hydrogen ions (or protons) as the only positive ion when dissolved in water. For example, hydrochloric acid (HCl) dissolves in water to form hydrogen ion (H+) and hydroxyl ion (OH-). This process is known as ionization. There are two main classes of acids :Organic acids and mineral or inorganic acids. The former occur as natural products in plants or animal materials while the later can be prepared from mineral elements or inorganic matter. Acids can also be grouped into Strong acids (ionizes completely) and Weak acids (ionizes partially).
Some organic and Inorganic acids
Organic acids Source Inorganic acids Constituents
Ethanoic acids Vinegar Hydrochloric acid Hydrogen, Chlorine
Citric acids Lime, Lemon Tetraoxosulphate (vi) acid Hydrogen ,Chlorine, Sulphur, Oxygen
Fatty acids Fats and Oil Trioxonitrate (v) acid Hydrogen, Nitrogen, Oxygen
BASICITY OF AN ACID
All acids in an aqueous solution yield hydrogen ions which can be replaced by metallic ion.
The basicity of an acid is the number of replaceable hydrogen ions, H+, in one molecule of the acid.
Characteristics of acids (Physical Properties)
a. Acids turn blue litmus paper red
b. They have sour taste; e.g. sour taste of unripe fruits
c. Strong acids are corrosive in concentrated form; e.g. HCl, H2SO4
EVALUATION
1. Define an acid and give two examples each of organic acid and inorganic acid
2. Differentiate between a strong acid and a weak acid. Give two examples of each.
3. (a) What is basicity? (b). Mention Four (4) physical properties of an acid.
(ii) Preparation of acids
a. Dissolving non-metallic oxide (acid anhydride) in water.
Carbon (iv) oxide dissolves in water to form weak acid, trioxocarbonate (iv) acid.
CO2(g) + H2O(l) H2CO3(aq)
b. Direct combination of constituent elements.
Hydrogen reacts directly with Halogens in the presence of catalyst to form halogen acids gas which dissolves readily in water to form acid.
activated charcoal
H2(g)+ Cl2(g) 2HCl(g)
heat
Heating Hydrogen gas and bromine vapour, in the presence of platinum as the catalyst, produces hydrogen bromide gas, which dissolves readily in water to form hydrobromic acid.
Platinum
H2(g) + Br2(g) 2HBr(g)
heat
c. Displacement of weak or volatile acid from its salt by a strong acid.
Concentrated H2SO4 is stronger but less volatile than HCl and, H2SO4 can therefore be used to displace the weaker HCl acid from its salt (NaCl).
NaCl(s) + H2SO4(aq) NaHSO4(aq) + HCl(g)
The hydrogen chloride gas formed dissolved in water readily to produce hydrogen chloride acid.
(iii) Reaction of acids (Chemical Properties)
a. Reaction of acid with metals
Acid react with some metals to liberate hydrogen gas.
Zn(s)+ 2HCl (aq) ZnCl2(aq) + H2(g)
Mg(s) + H2SO4 (a q) MgSO4+ H2(g)
NOTE:Dilute HNO3 does not react with metals to produce hydrogen gas.
b. Reaction of acids with Base and Alkalis.
Dilute acids react with bases and alkalis to form salts and water (known as neutralization reaction)
HCl (aq) + NaOH (aq) NaCl (aq) + H2O(l)
H2SO4(aq) + CaO(aq) CaSO4(aq) + H2O(l)
c. Reaction of acids with Trioxocarbonate (iv) and hydrogen trioxocarbonate (iv).
Acid reacts with CO32-or HCO3- to liberate carbon (iv) oxide (CO2).
NaCO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)
NaHCO3 + HCl(aq) NaHCll(aq) + H2O(l) + CO2(g)
(iv) Uses of acids
Name
Use
Hydrochloric acid • in industries to make chemicals
• to remove rust
Tetraoxosulphate (vi) acid • to make chemicals
• as drying and dehydrating agent
• as electrolyte in lead-acid accumulators
trrioxonitrate (v) acid • for making fertilizers, explosives, etc.
Acetic acid (ethanoic) • In preserving food
• In dyeing silk and other textiles.
Tartaric • In making baking soda, soft drinks and health salt
Citric acid • In making fruit juice
Fatty acids (e.g. palmitic and stearic acids) • In manufacturing soap. ( A process known as Saponification)
EVALUATION
1. Describe one method of preparing an acid
2. What is neutralization?
3. Give five (5) uses of an acid
4. Mention two (2) chemical properties of acids with examples.
GENERAL EVALUATION
OBJECTIVE TEST:
1. A weak acid is one which A. is not corrosive B. is slightly ionized in water. C. does not produce salts with alkalis. D. form acid salt with water E. does not conduct an electric current in aqueous solution.
2. The number of replaceable hydrogen atoms in one molecule of an acid indicates its
A. basicity B. acidity C. alkalinity D. reactivity E. pH value.
3. Which gas is liberated when acid react with metals.
A.O2 B. H2 C. CO2 D.NO2 E. CO.
4. Reaction of acid and base to produce salt and water is A. precipitation B. neutralization C. evaporation
D. decantation E.reaction.
5. H2(g) + Cl2(g) 2HCl(g). The catalyst in this reaction is
Heat
A. activated charcoal B. platinum C. yeast D. heat E.
ESSAY QUESTIONS:
1. (a) Give three physical properties of an acid. (b). Write an equation for the reaction between iron fillings and tetraoxosulpate (vi) acid.
2. State how hydrogen chloride gas can be obtained from tetraoxosulphate (vi) acid
3. (a) What is basicity? (b). State the basicity of the following acids: i. HNO3 ii. H2SO4 iii. CH3COOH.
4. State the natural source of i. ethanoic acid ii. Citric acid iii. Amino acid
5. (a) Why is ethanoic acid regarded as weak acid? (b). Hydrochloric acid is regarded as a strong acid. Why?
WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 97 - 100
PRE–READING ASSIGNMENT:
Read about Bases and Alkalis
WEEKEND ACTIVITY:
How are bases prepared and, what are their characteristics?
CONTENTS:
(1) ACIDS
i. Definition of acids
ii. Characteristics of acids
iii. Preparation of acids
iv. Reactions of acids
v. Uses of acids
Sub-topic1: ACIDS
Acids are associated with the sour taste we feel when we take fruits such as lemon, lime and oranges especially when they are not ripe. Palm wine left open in the air becomes sour because of the formation of an acid.
(i) Definition of acids: An acid is a substance which produces hydrogen ions (or protons) as the only positive ion when dissolved in water. For example, hydrochloric acid (HCl) dissolves in water to form hydrogen ion (H+) and hydroxyl ion (OH-). This process is known as ionization. There are two main classes of acids :Organic acids and mineral or inorganic acids. The former occur as natural products in plants or animal materials while the later can be prepared from mineral elements or inorganic matter. Acids can also be grouped into Strong acids (ionizes completely) and Weak acids (ionizes partially).
Some organic and Inorganic acids
Organic acids Source Inorganic acids Constituents
Ethanoic acids Vinegar Hydrochloric acid Hydrogen, Chlorine
Citric acids Lime, Lemon Tetraoxosulphate (vi) acid Hydrogen ,Chlorine, Sulphur, Oxygen
Fatty acids Fats and Oil Trioxonitrate (v) acid Hydrogen, Nitrogen, Oxygen
BASICITY OF AN ACID
All acids in an aqueous solution yield hydrogen ions which can be replaced by metallic ion.
The basicity of an acid is the number of replaceable hydrogen ions, H+, in one molecule of the acid.
Characteristics of acids (Physical Properties)
a. Acids turn blue litmus paper red
b. They have sour taste; e.g. sour taste of unripe fruits
c. Strong acids are corrosive in concentrated form; e.g. HCl, H2SO4
EVALUATION
1. Define an acid and give two examples each of organic acid and inorganic acid
2. Differentiate between a strong acid and a weak acid. Give two examples of each.
3. (a) What is basicity? (b). Mention Four (4) physical properties of an acid.
(ii) Preparation of acids
a. Dissolving non-metallic oxide (acid anhydride) in water.
Carbon (iv) oxide dissolves in water to form weak acid, trioxocarbonate (iv) acid.
CO2(g) + H2O(l) H2CO3(aq)
b. Direct combination of constituent elements.
Hydrogen reacts directly with Halogens in the presence of catalyst to form halogen acids gas which dissolves readily in water to form acid.
activated charcoal
H2(g)+ Cl2(g) 2HCl(g)
heat
Heating Hydrogen gas and bromine vapour, in the presence of platinum as the catalyst, produces hydrogen bromide gas, which dissolves readily in water to form hydrobromic acid.
Platinum
H2(g) + Br2(g) 2HBr(g)
heat
c. Displacement of weak or volatile acid from its salt by a strong acid.
Concentrated H2SO4 is stronger but less volatile than HCl and, H2SO4 can therefore be used to displace the weaker HCl acid from its salt (NaCl).
NaCl(s) + H2SO4(aq) NaHSO4(aq) + HCl(g)
The hydrogen chloride gas formed dissolved in water readily to produce hydrogen chloride acid.
(iii) Reaction of acids (Chemical Properties)
a. Reaction of acid with metals
Acid react with some metals to liberate hydrogen gas.
Zn(s)+ 2HCl (aq) ZnCl2(aq) + H2(g)
Mg(s) + H2SO4 (a q) MgSO4+ H2(g)
NOTE:Dilute HNO3 does not react with metals to produce hydrogen gas.
b. Reaction of acids with Base and Alkalis.
Dilute acids react with bases and alkalis to form salts and water (known as neutralization reaction)
HCl (aq) + NaOH (aq) NaCl (aq) + H2O(l)
H2SO4(aq) + CaO(aq) CaSO4(aq) + H2O(l)
c. Reaction of acids with Trioxocarbonate (iv) and hydrogen trioxocarbonate (iv).
Acid reacts with CO32-or HCO3- to liberate carbon (iv) oxide (CO2).
NaCO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)
NaHCO3 + HCl(aq) NaHCll(aq) + H2O(l) + CO2(g)
(iv) Uses of acids
Name
Use
Hydrochloric acid • in industries to make chemicals
• to remove rust
Tetraoxosulphate (vi) acid • to make chemicals
• as drying and dehydrating agent
• as electrolyte in lead-acid accumulators
trrioxonitrate (v) acid • for making fertilizers, explosives, etc.
Acetic acid (ethanoic) • In preserving food
• In dyeing silk and other textiles.
Tartaric • In making baking soda, soft drinks and health salt
Citric acid • In making fruit juice
Fatty acids (e.g. palmitic and stearic acids) • In manufacturing soap. ( A process known as Saponification)
EVALUATION
1. Describe one method of preparing an acid
2. What is neutralization?
3. Give five (5) uses of an acid
4. Mention two (2) chemical properties of acids with examples.
GENERAL EVALUATION
OBJECTIVE TEST:
1. A weak acid is one which A. is not corrosive B. is slightly ionized in water. C. does not produce salts with alkalis. D. form acid salt with water E. does not conduct an electric current in aqueous solution.
2. The number of replaceable hydrogen atoms in one molecule of an acid indicates its
A. basicity B. acidity C. alkalinity D. reactivity E. pH value.
3. Which gas is liberated when acid react with metals.
A.O2 B. H2 C. CO2 D.NO2 E. CO.
4. Reaction of acid and base to produce salt and water is A. precipitation B. neutralization C. evaporation
D. decantation E.reaction.
5. H2(g) + Cl2(g) 2HCl(g). The catalyst in this reaction is
Heat
A. activated charcoal B. platinum C. yeast D. heat E.
ESSAY QUESTIONS:
1. (a) Give three physical properties of an acid. (b). Write an equation for the reaction between iron fillings and tetraoxosulpate (vi) acid.
2. State how hydrogen chloride gas can be obtained from tetraoxosulphate (vi) acid
3. (a) What is basicity? (b). State the basicity of the following acids: i. HNO3 ii. H2SO4 iii. CH3COOH.
4. State the natural source of i. ethanoic acid ii. Citric acid iii. Amino acid
5. (a) Why is ethanoic acid regarded as weak acid? (b). Hydrochloric acid is regarded as a strong acid. Why?
WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 97 - 100
PRE–READING ASSIGNMENT:
Read about Bases and Alkalis
WEEKEND ACTIVITY:
How are bases prepared and, what are their characteristics?
WEEK 2
TOPIC: ACIDS, BASES AND SALTS
CONTENTS:
(2)BASES
i. Definition of bases
ii. Characteristics of bases
iii. Preparation of bases
iv. Reactions of bases
v. Uses of bases
(3) Relative acidity and alkalinity (the pH scale)
Sub-topic2: BASES
(i) Definition of bases
A base is a substance which will neutralize an acid to yield salt and water only. It is either an oxide or hydroxide of a metal, e.g sodium oxide, magnesium hydroxide, etc, while; an alkaline is a basic hydroxide which is soluble in water. Bases that are soluble in water are referred to as alkalis. Examples are sodium hydroxide (NaOH), potassium hydroxide (KOH), Mg (OH)2,
Oxides of heavy metals like PbO, ZnO and CuO are insoluble in water and are therefore bases not alkalis. CaO and MgO are slightly soluble and are alkalis. Like acids, alkalis may be strong or weak.
(ii) Characteristics of bases
1. Bases are soapy to touch, e.g. NaOH
2. They have bitter taste, e.g. lime water
3. They turn red litmus blue
4. Concentrated form of the caustic alkalis, NaOH and KOH are corrosive
5. They are electrolytes
(iii) Preparation of bases
Combustion of a reactive metal in air. When electropositive metals are heated in oxygen, they form metallic oxides.
2Ca + O2 CaO(s)
By reaction of metals with water (steam)
Ca + H2O Ca (OH)2 + H2
Decomposition of metal hydroxides by heating
heat
Ca (OH)2 CaO + H2O
heat
Cu(OH)2 CuO + H2O
Precipitation or double decomposition reaction
CuSO4 + 2NaOH Cu(OH)2 + Na2SO4
Dissolution of metallic oxides in water
Na2O + H2O NaOH
K2O + H2O 2KOH
EVALUATION
1) What is a base? Give three examples.
2) (a) Differentiate between a base and an alkaline. (b) Give three uses of base
3) State three properties of bases and, mention four methods of their preparation with examples.
(iv) Reaction of bases
Reaction with acid: all bases react with acids to form salt and water only
NaOH + HCl NaCl + H2O
Reaction of metallic hydroxide with heat
Zn (OH)2 ZnO + H2O
heat
Reaction with ammonium salts: alkali reacts with ammonium salts in the presence of heat to liberate ammonia gas.
2NH4Cl + Ca(OH)2 CaCl2 + 2NH3 + 2H2O
NaOH + NH4NO3 NaHNO3 + H2O + NH3
(v) Uses of bases
1. NaOH is the most common base and is very soluble, hence its used as a drying agent.
2. Bases are used in the making of soap.
3. Ca(OH)2 is used in the neutralization of soil acidity.
4. Mg(OH)2 is used in the production of toothpaste.
5. Ca(OH)2 is used in the making of mortar, plaster of Paris, white wash and cement and sugar refining.
6. NH4OH is used in weak solution as a common cleanser and grease solvent.
7. NH3 is used in making fertilizers and detergents.
(vi) Relative acidity and alkalinity (the pH scale)
The term pH denotes hydrogen ion index. It is a number-scale used to express the degree of acidity or alkalinity of a solution and, the number ranges from 0 to 14. A solution with pH value of less than 7 is acidic while that with a value greater than 7 is alkaline. A solution with pH of 7 is neutral i.e. it is neither acidic nor alkaline. The pH of a solution can be measured with an instrument called pH meter.
Colour
pH number Acid / Base
Red 1 – 3 Very acidic
Orange 4 – 5 Weak acid
Yellow 6 Very weak acid
Green 7 Neutral
Blue 8 Very weak base
Indigo 9 – 10 Weak base
Violet 11 – 14 Very basic
pH range and colour changes of universal indicator
Logarithmic pH scale: Sorensen, in 1909, introduced the logarithmic pH scale to eliminate the inconvenience encountered when using negative indices and to give room for wide range of [H+]and [OH-] concentrations that we do come across in acid-base reactions. He defined pH as the negative logarithm of the hydrogen ion concentration to the base 10. For example, if the hydrogen ion concentration of an aqueous medium is 10-5 mol dm-3, the acidity of the solution could be written in terms of pH as follows:
[H+] = 10-5
Log [H+] = log 10-5 = -5
PH = -log [H+] = - (- 5) = 5
Thus, if [H+] is 10-x, then pH = x
Proportional to each other:
[H+] [OH-] = 10-14
PH+ POH = 14, where POH is the hydrogen ion index
POH = 14 – pH
Note: A high pH value indicates low H+ concentration (weak acidity) and a high OH- concentration (strong alkalinity). At neutrality, [H+] = [OH-] = 10-7
Worked Example
1. Calculate the pH of 0.005 moldm-3 tetraoxosulphate (vi).
Solution
H2SO4 2H+ + SO42-
H+= [2 x 0.005] moldm-3
= 0.001 = 1 x 10-2
PH = -log [H+]
PH = -log [1 x 10-2]
PH = 2
EVALUATION
1) Describe two chemical properties of bases with examples.
2) Give 5 uses of bases with one example each.
3) (a) Define the term PH. (b) Calculate the OH- concentration of 0.01 M tetraoxosulphate (VI) acid solution.
GENERAL EVALUATION
OBJECTIVE TEST:
1. PH of 0.001 M acid is A. 2 B. 3 C. 4 D. 1 E. 5
2. Which pH value indicates a basic solution? A.-1 B. 7 C. 0 D. 3 E. 9
3. A solution of pH 7 is A. acidic B. basic C. neutral D. alkaline E. salty.
4. Bases can be prepared by the following method except: A. Combustion of a reactive metal in air. B. Dissolution of metallic oxides in water. C. By reaction of metals with water (steam). D. Precipitation or double decomposition reaction. E. Heating Hydrogen gas and bromine vapour.
5. Which is correct? Zn (OH)2 + Heat H2O + ? A. ZnO B. ZnO2 C. H2 D. ZnCl2 E. O2
ESSAY QUESTIONS
1. Mention 3 different methods by which you could prepare bases in the laboratory. Write an equation to illustrate each method.
2. (a). Define pH and POH. (b) What is the relation pH and POH of an aqueous solution? (c) Determine the pH of a solution containing 0.05moldm-3 NaCO3.
3. Distinguish between (i) a strong base and a week base. (ii) a Base and an Alkaline.
4. A glass cup of orange juice is found to have POH of 11.40. Calculate the concentration of the hydrogen ions in the juice.
5. Find the hydrogen ion, H+ and hydroxide ion, OH- concentration in 0.02M solution of H2SO4. WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 100 - 104
PRE–READING ASSIGNMENT:
Read up Salts.
WEEKEND ACTIVITY
• List three Deliquescent and Hygroscopic substances each.
• Mention five types of salts.
CONTENTS:
(2)BASES
i. Definition of bases
ii. Characteristics of bases
iii. Preparation of bases
iv. Reactions of bases
v. Uses of bases
(3) Relative acidity and alkalinity (the pH scale)
Sub-topic2: BASES
(i) Definition of bases
A base is a substance which will neutralize an acid to yield salt and water only. It is either an oxide or hydroxide of a metal, e.g sodium oxide, magnesium hydroxide, etc, while; an alkaline is a basic hydroxide which is soluble in water. Bases that are soluble in water are referred to as alkalis. Examples are sodium hydroxide (NaOH), potassium hydroxide (KOH), Mg (OH)2,
Oxides of heavy metals like PbO, ZnO and CuO are insoluble in water and are therefore bases not alkalis. CaO and MgO are slightly soluble and are alkalis. Like acids, alkalis may be strong or weak.
(ii) Characteristics of bases
1. Bases are soapy to touch, e.g. NaOH
2. They have bitter taste, e.g. lime water
3. They turn red litmus blue
4. Concentrated form of the caustic alkalis, NaOH and KOH are corrosive
5. They are electrolytes
(iii) Preparation of bases
Combustion of a reactive metal in air. When electropositive metals are heated in oxygen, they form metallic oxides.
2Ca + O2 CaO(s)
By reaction of metals with water (steam)
Ca + H2O Ca (OH)2 + H2
Decomposition of metal hydroxides by heating
heat
Ca (OH)2 CaO + H2O
heat
Cu(OH)2 CuO + H2O
Precipitation or double decomposition reaction
CuSO4 + 2NaOH Cu(OH)2 + Na2SO4
Dissolution of metallic oxides in water
Na2O + H2O NaOH
K2O + H2O 2KOH
EVALUATION
1) What is a base? Give three examples.
2) (a) Differentiate between a base and an alkaline. (b) Give three uses of base
3) State three properties of bases and, mention four methods of their preparation with examples.
(iv) Reaction of bases
Reaction with acid: all bases react with acids to form salt and water only
NaOH + HCl NaCl + H2O
Reaction of metallic hydroxide with heat
Zn (OH)2 ZnO + H2O
heat
Reaction with ammonium salts: alkali reacts with ammonium salts in the presence of heat to liberate ammonia gas.
2NH4Cl + Ca(OH)2 CaCl2 + 2NH3 + 2H2O
NaOH + NH4NO3 NaHNO3 + H2O + NH3
(v) Uses of bases
1. NaOH is the most common base and is very soluble, hence its used as a drying agent.
2. Bases are used in the making of soap.
3. Ca(OH)2 is used in the neutralization of soil acidity.
4. Mg(OH)2 is used in the production of toothpaste.
5. Ca(OH)2 is used in the making of mortar, plaster of Paris, white wash and cement and sugar refining.
6. NH4OH is used in weak solution as a common cleanser and grease solvent.
7. NH3 is used in making fertilizers and detergents.
(vi) Relative acidity and alkalinity (the pH scale)
The term pH denotes hydrogen ion index. It is a number-scale used to express the degree of acidity or alkalinity of a solution and, the number ranges from 0 to 14. A solution with pH value of less than 7 is acidic while that with a value greater than 7 is alkaline. A solution with pH of 7 is neutral i.e. it is neither acidic nor alkaline. The pH of a solution can be measured with an instrument called pH meter.
Colour
pH number Acid / Base
Red 1 – 3 Very acidic
Orange 4 – 5 Weak acid
Yellow 6 Very weak acid
Green 7 Neutral
Blue 8 Very weak base
Indigo 9 – 10 Weak base
Violet 11 – 14 Very basic
pH range and colour changes of universal indicator
Logarithmic pH scale: Sorensen, in 1909, introduced the logarithmic pH scale to eliminate the inconvenience encountered when using negative indices and to give room for wide range of [H+]and [OH-] concentrations that we do come across in acid-base reactions. He defined pH as the negative logarithm of the hydrogen ion concentration to the base 10. For example, if the hydrogen ion concentration of an aqueous medium is 10-5 mol dm-3, the acidity of the solution could be written in terms of pH as follows:
[H+] = 10-5
Log [H+] = log 10-5 = -5
PH = -log [H+] = - (- 5) = 5
Thus, if [H+] is 10-x, then pH = x
Proportional to each other:
[H+] [OH-] = 10-14
PH+ POH = 14, where POH is the hydrogen ion index
POH = 14 – pH
Note: A high pH value indicates low H+ concentration (weak acidity) and a high OH- concentration (strong alkalinity). At neutrality, [H+] = [OH-] = 10-7
Worked Example
1. Calculate the pH of 0.005 moldm-3 tetraoxosulphate (vi).
Solution
H2SO4 2H+ + SO42-
H+= [2 x 0.005] moldm-3
= 0.001 = 1 x 10-2
PH = -log [H+]
PH = -log [1 x 10-2]
PH = 2
EVALUATION
1) Describe two chemical properties of bases with examples.
2) Give 5 uses of bases with one example each.
3) (a) Define the term PH. (b) Calculate the OH- concentration of 0.01 M tetraoxosulphate (VI) acid solution.
GENERAL EVALUATION
OBJECTIVE TEST:
1. PH of 0.001 M acid is A. 2 B. 3 C. 4 D. 1 E. 5
2. Which pH value indicates a basic solution? A.-1 B. 7 C. 0 D. 3 E. 9
3. A solution of pH 7 is A. acidic B. basic C. neutral D. alkaline E. salty.
4. Bases can be prepared by the following method except: A. Combustion of a reactive metal in air. B. Dissolution of metallic oxides in water. C. By reaction of metals with water (steam). D. Precipitation or double decomposition reaction. E. Heating Hydrogen gas and bromine vapour.
5. Which is correct? Zn (OH)2 + Heat H2O + ? A. ZnO B. ZnO2 C. H2 D. ZnCl2 E. O2
ESSAY QUESTIONS
1. Mention 3 different methods by which you could prepare bases in the laboratory. Write an equation to illustrate each method.
2. (a). Define pH and POH. (b) What is the relation pH and POH of an aqueous solution? (c) Determine the pH of a solution containing 0.05moldm-3 NaCO3.
3. Distinguish between (i) a strong base and a week base. (ii) a Base and an Alkaline.
4. A glass cup of orange juice is found to have POH of 11.40. Calculate the concentration of the hydrogen ions in the juice.
5. Find the hydrogen ion, H+ and hydroxide ion, OH- concentration in 0.02M solution of H2SO4. WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 100 - 104
PRE–READING ASSIGNMENT:
Read up Salts.
WEEKEND ACTIVITY
• List three Deliquescent and Hygroscopic substances each.
• Mention five types of salts.
WEEK 3
TOPIC: ACIDS, BASES AND SALTS
CONTENTS:
SALTS
i. Definition of salts
ii. Characteristics of salts
iii. Preparation of salts
iv. Types of salts
v. Uses of salts
VI. Deliquescent and hygroscopic substances
VI. Solubility of salt in water
SUB-TOPIC: SALTS
(i) Definition of salts
A salt is formed when all or part of the ionizable hydrogen of an acid is replaced by metallic or ammonium ions. It consist of all aggregation of positively charged metallic ion and negatively charged acid ions.
(ii) Characteristics of salts
1. They contain water of crystallization. Water of crystallization is the definite amount of water that some substances chemically combine with when they form salt (hydrates). Examples of salt with water of crystallization are sodium trioxosulphate (iv) decahydrate, NaSO3 10H2O, Ion (II) tetraoxosulphate (vi) heptahydrate, FeSO4 7H2O, etc.
2. They effloresce. Efflorescence is the loss of part or all of the water of crystallization from a crystalline salt when exposed to the atmosphere to form a lower dehydrate or the anhydrous salt; e.g. NaCO3 10H2O (washing soda).
3. They are deliquescent. Deliquescence is a phenomenon in which a substance absorbed moisture (water) from the atmosphere when exposed and turn into solution; e.g. NaCl, FeCl3, KOH, CaCl, MgCl2, silica gel, etc.
4. Salts are hygroscopic. Hygroscopic is a phenomenon in which a substance absorbed moisture (water) from the atmosphere when exposed and does not turn into solution but merely become sticky or moist; e.g. sodium trioxonitrate (v), copper(II) oxide, quicklime. Hygroscopic substances are commonly employed as drying agents or desiccants. Drying agents or desiccants are substances that have strong tendency to absorb moisture or water. They are used to dry gases in the laboratory. A drying agent cannot be used if it reacts with the substance to be dried; that is why H2SO4 cannot be used to dry ammonia gas because they will react to form ammonium tetraoxosulphate (vi).
2NH3¬¬¬ + H2SO4 (NH4)2SO4
(iii) Preparation of salts
The method chosen to prepare a salt depends largely on (a) its solubility in water (b) its stability to heat.
Preparation of soluble salts
Reaction of acid and metal: Here, the more reactive metal (Ca, Mg, Zn, Fe), directly displaces the hydrogen ion in the acid; e.g. Zn + HCl ZnCl2 + H2
Reaction of alkaline and acid: Salts are formed when acid reacts with alkaline; e.g KOH + HNO3 KNO3 + H2O
Dilute acid and insoluble base: A salt is formed when a dilute acid is heated and the insoluble base is added to the acid until no more bases can dissolve in the acid.
Preparation of insoluble salts
Double decomposition: This is done by missing two compounds, one containing the metallic radical and the other the acidic radical of the required insoluble salt; e.g. H2SO4 + CuO CuSO4 + H2O
Combination of constituent elements: This involves the combination of the elements that make up the insoluble salt; e.g. Fe + S FeS
2Fe + 3Cl2 2FeCl3
EVALU ATION
1) State three properties of salts with two examples each.
2) Name two salts which can be prepared by titration and, describe two methods of preparing soluble salts.
3) Explain with two examples the term efflorescence
4) When is a substance said to be deliquescence. Explain with examples.
5) Common salt (NaCl) becomes wet on exposure to air. Explain.
6) What are dehydrating agents? Explain the function of fused calcium (II) chloride in the desiccator.
(iv) Types of salts
There are five main types of salts. They are: normal salts, acid salts, basic salts, double salts and complex salts.
• Normal salt: Formed when all the replaceable hydrogen ions in the acid have been completely replaced by metallic ions. They are neutral to litmus paper, e.g.
H2SO4+ ZnO H2O + ZnSO
HCl + NaOH NaCl + H2O
• Acid salt: Formed when the replaceable hydrogen ions in acids are only partially replaced by a metal and are acidic to litmus paper; e.g.
H2SO4+ NaOH NaHSO4 + H2O
• Basic salt: Formed when there is an insufficient acid to neutralize a base; e.g.
Ca (OH)2 + HCl Ca (OH) 2 + H2O
Zn (OH) Cl+ HCl ZnCl2 + H2O
• Double salt: Ionizes to produce three different types of ions in solution. Usually two of these are positive charged, while the other is negatively charged; e.g. potash alum or aluminum potassium tetraoxosulphate(vi)duodecahydrate, KAl (SO4)2. 12H2O
• Complex salt: Formed by mixing together two simple salts. They are characterized by formation of new ions called complex ions; e.g. sodium tetrahydroxozincate (II), Na2Zn(OH)4 and potassium hexacyanoferrate (II), K4Fe(CN)6.
(v) Uses of salts
1. Sodium chloride is used in preserving food
2. Salt are used as drying agents and antifreeze
3. Salt is used in soap making process to separate soap from glycerin
4. It is used in softening of water e.g. Na2CO3 10H2O
5. Used in Stabilizing dirty roads
6. Used in the production of toothpaste.
(E) Solubility of salts in water
When salt is dissolved in water a solution which is either acidic or basic is formed. The reaction of a salt with water to form acidic or basic solution is known as Hydrolysis. Normal salt dissolves in water to form neutral solution. However, when other salts are dissolved in water solutions that are not neutral are formed. These solutions may either be acidic or alkaline. Examples:NH4Cl + H2O NH4OH + HCl
CuSO4+ 2H2O Cu (OH) 2 + H2SO4
Na2CO3 + 2H2O NaOH + H2CO3
K2CO3+ 2H2O KOH +H2CO3
In general, salts formed strong acids and weak bases hydrolyze in water to acidic solutions, while salts formed strong bases and weak acids hydrolyze in water to form alkaline solutions.
EVALUATION
1) Give five types of salts with examples.
2) What are the uses of salts? Define hydrolysis.
3) Differentiate between a normal salt and acidic
4) What is salt? Give five examples.
GENERAL EVALUATION
OBJECTIVE TEST :
1. An example efflorescence compound is
A. BaCl B. KOH C. CaCl2D. NaOH E. Na2CO.10H2O
2. Which of the following compounds will solution when exposed to air?
A. Na2CO.10H2O B.NaNO3 C. CuSO4D. CaCl2 E. Na2SO4.10H2O
3. The following salts dissolve readily in water except
A.CaCl2 B. Na2SO4 C. (NH4) SO4D.PbSO4 E. Na2CO3¬
4. Alums are classified as (A.)Normal salt (B.)basic salt(C.)Double salt (D.) simple salt (E) Anhydrous salt
5. Water in crystalline salts provides
(A.) hydrated bonds and colour (B.) colour and shape(C). Colour and solubility base
Shape and crystal lattice (E). Colour and crystal lattice.
ESSAY QUESTIONS
1. Explain and give an example each of (a) deliquescent substance (b) hygroscopic substance (c) efflorescent substance.
2. Give three general methods of preparing salts. Give equations for the examples.
How would you prepare pure dry potassium trioxonitrate (v). (b) What product is always is obtained in the neutralization reaction?
3. Define is water of crystallization? Give two examples of salts that possess this water.
(a) What is salt? Give four examples. (b) What is obtained when water is driven out from a hydrated salt by heat?
WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 107 - 114
PRE–READING ASSIGNMENT:
Read about carbon and its compounds.
WEEKEND ACTIVITY
• What are diamonds?
• How is carbon (IV) oxide prepared?
CONTENTS:
SALTS
i. Definition of salts
ii. Characteristics of salts
iii. Preparation of salts
iv. Types of salts
v. Uses of salts
VI. Deliquescent and hygroscopic substances
VI. Solubility of salt in water
SUB-TOPIC: SALTS
(i) Definition of salts
A salt is formed when all or part of the ionizable hydrogen of an acid is replaced by metallic or ammonium ions. It consist of all aggregation of positively charged metallic ion and negatively charged acid ions.
(ii) Characteristics of salts
1. They contain water of crystallization. Water of crystallization is the definite amount of water that some substances chemically combine with when they form salt (hydrates). Examples of salt with water of crystallization are sodium trioxosulphate (iv) decahydrate, NaSO3 10H2O, Ion (II) tetraoxosulphate (vi) heptahydrate, FeSO4 7H2O, etc.
2. They effloresce. Efflorescence is the loss of part or all of the water of crystallization from a crystalline salt when exposed to the atmosphere to form a lower dehydrate or the anhydrous salt; e.g. NaCO3 10H2O (washing soda).
3. They are deliquescent. Deliquescence is a phenomenon in which a substance absorbed moisture (water) from the atmosphere when exposed and turn into solution; e.g. NaCl, FeCl3, KOH, CaCl, MgCl2, silica gel, etc.
4. Salts are hygroscopic. Hygroscopic is a phenomenon in which a substance absorbed moisture (water) from the atmosphere when exposed and does not turn into solution but merely become sticky or moist; e.g. sodium trioxonitrate (v), copper(II) oxide, quicklime. Hygroscopic substances are commonly employed as drying agents or desiccants. Drying agents or desiccants are substances that have strong tendency to absorb moisture or water. They are used to dry gases in the laboratory. A drying agent cannot be used if it reacts with the substance to be dried; that is why H2SO4 cannot be used to dry ammonia gas because they will react to form ammonium tetraoxosulphate (vi).
2NH3¬¬¬ + H2SO4 (NH4)2SO4
(iii) Preparation of salts
The method chosen to prepare a salt depends largely on (a) its solubility in water (b) its stability to heat.
Preparation of soluble salts
Reaction of acid and metal: Here, the more reactive metal (Ca, Mg, Zn, Fe), directly displaces the hydrogen ion in the acid; e.g. Zn + HCl ZnCl2 + H2
Reaction of alkaline and acid: Salts are formed when acid reacts with alkaline; e.g KOH + HNO3 KNO3 + H2O
Dilute acid and insoluble base: A salt is formed when a dilute acid is heated and the insoluble base is added to the acid until no more bases can dissolve in the acid.
Preparation of insoluble salts
Double decomposition: This is done by missing two compounds, one containing the metallic radical and the other the acidic radical of the required insoluble salt; e.g. H2SO4 + CuO CuSO4 + H2O
Combination of constituent elements: This involves the combination of the elements that make up the insoluble salt; e.g. Fe + S FeS
2Fe + 3Cl2 2FeCl3
EVALU ATION
1) State three properties of salts with two examples each.
2) Name two salts which can be prepared by titration and, describe two methods of preparing soluble salts.
3) Explain with two examples the term efflorescence
4) When is a substance said to be deliquescence. Explain with examples.
5) Common salt (NaCl) becomes wet on exposure to air. Explain.
6) What are dehydrating agents? Explain the function of fused calcium (II) chloride in the desiccator.
(iv) Types of salts
There are five main types of salts. They are: normal salts, acid salts, basic salts, double salts and complex salts.
• Normal salt: Formed when all the replaceable hydrogen ions in the acid have been completely replaced by metallic ions. They are neutral to litmus paper, e.g.
H2SO4+ ZnO H2O + ZnSO
HCl + NaOH NaCl + H2O
• Acid salt: Formed when the replaceable hydrogen ions in acids are only partially replaced by a metal and are acidic to litmus paper; e.g.
H2SO4+ NaOH NaHSO4 + H2O
• Basic salt: Formed when there is an insufficient acid to neutralize a base; e.g.
Ca (OH)2 + HCl Ca (OH) 2 + H2O
Zn (OH) Cl+ HCl ZnCl2 + H2O
• Double salt: Ionizes to produce three different types of ions in solution. Usually two of these are positive charged, while the other is negatively charged; e.g. potash alum or aluminum potassium tetraoxosulphate(vi)duodecahydrate, KAl (SO4)2. 12H2O
• Complex salt: Formed by mixing together two simple salts. They are characterized by formation of new ions called complex ions; e.g. sodium tetrahydroxozincate (II), Na2Zn(OH)4 and potassium hexacyanoferrate (II), K4Fe(CN)6.
(v) Uses of salts
1. Sodium chloride is used in preserving food
2. Salt are used as drying agents and antifreeze
3. Salt is used in soap making process to separate soap from glycerin
4. It is used in softening of water e.g. Na2CO3 10H2O
5. Used in Stabilizing dirty roads
6. Used in the production of toothpaste.
(E) Solubility of salts in water
When salt is dissolved in water a solution which is either acidic or basic is formed. The reaction of a salt with water to form acidic or basic solution is known as Hydrolysis. Normal salt dissolves in water to form neutral solution. However, when other salts are dissolved in water solutions that are not neutral are formed. These solutions may either be acidic or alkaline. Examples:NH4Cl + H2O NH4OH + HCl
CuSO4+ 2H2O Cu (OH) 2 + H2SO4
Na2CO3 + 2H2O NaOH + H2CO3
K2CO3+ 2H2O KOH +H2CO3
In general, salts formed strong acids and weak bases hydrolyze in water to acidic solutions, while salts formed strong bases and weak acids hydrolyze in water to form alkaline solutions.
EVALUATION
1) Give five types of salts with examples.
2) What are the uses of salts? Define hydrolysis.
3) Differentiate between a normal salt and acidic
4) What is salt? Give five examples.
GENERAL EVALUATION
OBJECTIVE TEST :
1. An example efflorescence compound is
A. BaCl B. KOH C. CaCl2D. NaOH E. Na2CO.10H2O
2. Which of the following compounds will solution when exposed to air?
A. Na2CO.10H2O B.NaNO3 C. CuSO4D. CaCl2 E. Na2SO4.10H2O
3. The following salts dissolve readily in water except
A.CaCl2 B. Na2SO4 C. (NH4) SO4D.PbSO4 E. Na2CO3¬
4. Alums are classified as (A.)Normal salt (B.)basic salt(C.)Double salt (D.) simple salt (E) Anhydrous salt
5. Water in crystalline salts provides
(A.) hydrated bonds and colour (B.) colour and shape(C). Colour and solubility base
Shape and crystal lattice (E). Colour and crystal lattice.
ESSAY QUESTIONS
1. Explain and give an example each of (a) deliquescent substance (b) hygroscopic substance (c) efflorescent substance.
2. Give three general methods of preparing salts. Give equations for the examples.
How would you prepare pure dry potassium trioxonitrate (v). (b) What product is always is obtained in the neutralization reaction?
3. Define is water of crystallization? Give two examples of salts that possess this water.
(a) What is salt? Give four examples. (b) What is obtained when water is driven out from a hydrated salt by heat?
WEEKEND ASSIGNMENT:
New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 107 - 114
PRE–READING ASSIGNMENT:
Read about carbon and its compounds.
WEEKEND ACTIVITY
• What are diamonds?
• How is carbon (IV) oxide prepared?
WEEK 4
TOPIC: WATER
CONTENT:
1. Source of water
2. Types of water (Soft and hard)
3. Water pollutants
4. Uses of water
5. Laboratory preparation of water
WATER
“Water is Life”. It is the most important and the most abundant on earth. It is of great importance to all plants and animals. The human body is over 6o percent water and it is present in equally the same amount in plants. It should however be noted that water is not available everywhere and its availability at certain parts of the world has led to the influx of man to those areas to set up villages and towns.
Sub-topic 1. Source of Water: Water can either be found as a natural source or as treated water. There many types of sources of water found on the earth’s surface. The include rain water, spring water, well-water, river water, lake water and sea-water. Rain water is the purest form of natural water because it is formed as a result condensation of water in the atmosphere. Spring water contains a considerable amount of mineral salt; but very little suspended impurities such as dust and bacteria. Well-water contains a lot or clay and other mineral salts. Deep well-water tends to be less polluted than surface well-water. River water, Lake water, and Sea-water contain a lot of dissolved air, mineral salts, bacteria and organic remains.
All these waters have to be purified before they can be used for drinking. And all the type of natural water are in constant circulation, forming a gigantic water cycle.
TREATED WATER
Treated water are usually prepared for special purposes. Examples are distilled water, pipe-borne water for townships and chlorinated water used in swimming pool.
DISTILLED WATER
Distilled water is chemically pure water prepared by condensing steam using Lie big condenser. If ion exchange resin is used in preparing the water, it is called ionized water.
Sub-topic 2: Types of water
Water is of two types namely: Soft water and Hard water.
(a) Soft water: Water is said to be soft if it readily forms lather with soap. Examples are rain water, tap water.
(b) Hard water: Hard water is water which will not form lather with soap. Examples are river water, lake water, stream water and sea water.
Types of hard water.
There are two types of hard water namely:
(i). Temporary hard water: This the hardness caused by the presence of dissolved Ca(HCO3) and MgCO3 in water and can be removed by boiling.
(ii) Permanent hardness: This is the hardness caused by the presence of CaSO3, MgSO3 and chlorides which cannot be removed by boiling but by addition of washing soda, caustic soda and ion exchange method.
Advantages of hard water
i. It has pleasant taste than soft water and tasteless water.
ii. It does not dissolve lead pipes of pots unlike soft water which dissolves led pipes.
iii. It is good for healthy teeth and bones because it contains calcium which is an important element in formation of teeth and bones of animals.
iv. Animals like snail and crabs are able to make their shell with the help of hard water.
Disadvantages of hard water
i. It causes furring of kettle and boilers unlike soft water.
ii. It infers with processes used to dye materials and tan hides.
iii. It forms scum with soap thus, wasting soap unlike soft water.
EVALUATION
1. What are the natural sources of water
2. Differentiate between soft water and hard water
3. Mention three (3) advantages and two (2) disadvantages of hard water
Sub-topic 3: Water pollutants
The common pollutants are as follows:
(a). Crude oil spill: Accidents and carelessness in oil rigs and tankers cause oil spills mainly in the coaster waters. The oil floats on water and kills most of the marine life in the affected areas. The oil is then washed up on the beach, temporarily preventing people from using the water for recreation.
(b). Industrial and agricultural waste: Chemical wastes from industries and agriculture; such as acids, organic solvents, mercury compounds, fertilizers, insecticides, etc that are emptied directly into rivers untreated causes water pollution and endangers aquatic life. For instance, mercury compounds accumulate in the body of the aquatic organism like fish and this eventually causes food poison in the animal that feeds on such fish.
(c) Refuge and sewage: It is common practice to see people dump refuse and human wastes into a nearby river. Most of these refuge and sewage are pollutants which are biodegradable i.e. they can decomposed by decomposers such as bacteria which uses up the oxygen present in the water.
Sub-topic 4: Uses of water
i. Water is used for cooking and drinking.
ii. It is used as a means of transport.
iii. It is used in the manufacturing of drugs.
iv. It is also used in car batteries
v. It is used in the laboratory for preparing reagents and for carrying out analysis.
Sub-topic 5: Laboratory preparation of water
Water is prepared from its constituent elements, i.e. hydrogen and oxygen. Hydrogen is generated by the action of fairly concentrated hydrochloric acid on zinc. The gas then passed through a U-tube containing anhydrous calcium chloride gas, the hydrogen is burnt at a jet and the vapours are ‘cooled’ when they come in contact with a clean can kept cool by water. A test tube is placed over the jet to collect hydrogen gas by displacement of air. When the test tube is full of gas, it burns on the application of to it, light the jet and allow the flame to burn very close to the can. Moisture will condense on the can and will drop into a dish which is placed below the liquid.
The liquid can be shown as water using:
• Action of the liquid on anhydrous copper (III) tetraoxosulphate (VI).
• Boiling point of the water.
EVALUATION
1. What are the pollutants that can be present in water
2. (a) Give four uses of water. (b) How can water be prepared in the laboratory?
3. Distinguish distilled water from treated water.
GENERAL EVALUATION
OBJECTIVE TEST
1. One of these is not a water pollutant: A. petroleum B. industrial effluents C. biodegradable chemicals D. domestic liquid and solid water E. water
2. Temporal hardness of water is removed by the use of the following except: A. boiling B. use of alum C. use of Na2CO3 D. use of Ca(OH)2 E. MgSO4
3. Water is temporarily hard because it contains A. CaSO4 B. MgSO4 C. Chlorine D. Ca(HCO3)2 E. KNO3
4. Natural water collected from rivers and ponds contain oxygen, CO2 and A. hydrogen B. nitrogen C. SO2 D. Chlorine E. potassium.
5. A sample of water which has passed through a de-ionizer may contain A. temporal hardness B. permanent hardness C. Heavy metal ions D. organic impurities.
ESSAY QUESTIONS
1(a). Mention two types of hardness of water
(b). list two salts that cause each of them.
2. Describe an experiment to show that contains hydrogen and oxygen only
3.What term is used to describe water sample that: (a) produce lather with soap (b) does not
produce lather with soap.
4.State two advantages of soft water over hard water. (b) list two advantages of hard water.
5.Enumerate three water pollutants you know.
WEEKEND ASSIGNMENT:
Read New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 298 - 302
PRE–READING ASSIGNMENT:
Read about carbon and its compounds.
WEEKEND ACTIVITY
(a)Describe the structure of carbon atom and its properties.(b) What are the allotropes of carbon.
CONTENT:
1. Source of water
2. Types of water (Soft and hard)
3. Water pollutants
4. Uses of water
5. Laboratory preparation of water
WATER
“Water is Life”. It is the most important and the most abundant on earth. It is of great importance to all plants and animals. The human body is over 6o percent water and it is present in equally the same amount in plants. It should however be noted that water is not available everywhere and its availability at certain parts of the world has led to the influx of man to those areas to set up villages and towns.
Sub-topic 1. Source of Water: Water can either be found as a natural source or as treated water. There many types of sources of water found on the earth’s surface. The include rain water, spring water, well-water, river water, lake water and sea-water. Rain water is the purest form of natural water because it is formed as a result condensation of water in the atmosphere. Spring water contains a considerable amount of mineral salt; but very little suspended impurities such as dust and bacteria. Well-water contains a lot or clay and other mineral salts. Deep well-water tends to be less polluted than surface well-water. River water, Lake water, and Sea-water contain a lot of dissolved air, mineral salts, bacteria and organic remains.
All these waters have to be purified before they can be used for drinking. And all the type of natural water are in constant circulation, forming a gigantic water cycle.
TREATED WATER
Treated water are usually prepared for special purposes. Examples are distilled water, pipe-borne water for townships and chlorinated water used in swimming pool.
DISTILLED WATER
Distilled water is chemically pure water prepared by condensing steam using Lie big condenser. If ion exchange resin is used in preparing the water, it is called ionized water.
Sub-topic 2: Types of water
Water is of two types namely: Soft water and Hard water.
(a) Soft water: Water is said to be soft if it readily forms lather with soap. Examples are rain water, tap water.
(b) Hard water: Hard water is water which will not form lather with soap. Examples are river water, lake water, stream water and sea water.
Types of hard water.
There are two types of hard water namely:
(i). Temporary hard water: This the hardness caused by the presence of dissolved Ca(HCO3) and MgCO3 in water and can be removed by boiling.
(ii) Permanent hardness: This is the hardness caused by the presence of CaSO3, MgSO3 and chlorides which cannot be removed by boiling but by addition of washing soda, caustic soda and ion exchange method.
Advantages of hard water
i. It has pleasant taste than soft water and tasteless water.
ii. It does not dissolve lead pipes of pots unlike soft water which dissolves led pipes.
iii. It is good for healthy teeth and bones because it contains calcium which is an important element in formation of teeth and bones of animals.
iv. Animals like snail and crabs are able to make their shell with the help of hard water.
Disadvantages of hard water
i. It causes furring of kettle and boilers unlike soft water.
ii. It infers with processes used to dye materials and tan hides.
iii. It forms scum with soap thus, wasting soap unlike soft water.
EVALUATION
1. What are the natural sources of water
2. Differentiate between soft water and hard water
3. Mention three (3) advantages and two (2) disadvantages of hard water
Sub-topic 3: Water pollutants
The common pollutants are as follows:
(a). Crude oil spill: Accidents and carelessness in oil rigs and tankers cause oil spills mainly in the coaster waters. The oil floats on water and kills most of the marine life in the affected areas. The oil is then washed up on the beach, temporarily preventing people from using the water for recreation.
(b). Industrial and agricultural waste: Chemical wastes from industries and agriculture; such as acids, organic solvents, mercury compounds, fertilizers, insecticides, etc that are emptied directly into rivers untreated causes water pollution and endangers aquatic life. For instance, mercury compounds accumulate in the body of the aquatic organism like fish and this eventually causes food poison in the animal that feeds on such fish.
(c) Refuge and sewage: It is common practice to see people dump refuse and human wastes into a nearby river. Most of these refuge and sewage are pollutants which are biodegradable i.e. they can decomposed by decomposers such as bacteria which uses up the oxygen present in the water.
Sub-topic 4: Uses of water
i. Water is used for cooking and drinking.
ii. It is used as a means of transport.
iii. It is used in the manufacturing of drugs.
iv. It is also used in car batteries
v. It is used in the laboratory for preparing reagents and for carrying out analysis.
Sub-topic 5: Laboratory preparation of water
Water is prepared from its constituent elements, i.e. hydrogen and oxygen. Hydrogen is generated by the action of fairly concentrated hydrochloric acid on zinc. The gas then passed through a U-tube containing anhydrous calcium chloride gas, the hydrogen is burnt at a jet and the vapours are ‘cooled’ when they come in contact with a clean can kept cool by water. A test tube is placed over the jet to collect hydrogen gas by displacement of air. When the test tube is full of gas, it burns on the application of to it, light the jet and allow the flame to burn very close to the can. Moisture will condense on the can and will drop into a dish which is placed below the liquid.
The liquid can be shown as water using:
• Action of the liquid on anhydrous copper (III) tetraoxosulphate (VI).
• Boiling point of the water.
EVALUATION
1. What are the pollutants that can be present in water
2. (a) Give four uses of water. (b) How can water be prepared in the laboratory?
3. Distinguish distilled water from treated water.
GENERAL EVALUATION
OBJECTIVE TEST
1. One of these is not a water pollutant: A. petroleum B. industrial effluents C. biodegradable chemicals D. domestic liquid and solid water E. water
2. Temporal hardness of water is removed by the use of the following except: A. boiling B. use of alum C. use of Na2CO3 D. use of Ca(OH)2 E. MgSO4
3. Water is temporarily hard because it contains A. CaSO4 B. MgSO4 C. Chlorine D. Ca(HCO3)2 E. KNO3
4. Natural water collected from rivers and ponds contain oxygen, CO2 and A. hydrogen B. nitrogen C. SO2 D. Chlorine E. potassium.
5. A sample of water which has passed through a de-ionizer may contain A. temporal hardness B. permanent hardness C. Heavy metal ions D. organic impurities.
ESSAY QUESTIONS
1(a). Mention two types of hardness of water
(b). list two salts that cause each of them.
2. Describe an experiment to show that contains hydrogen and oxygen only
3.What term is used to describe water sample that: (a) produce lather with soap (b) does not
produce lather with soap.
4.State two advantages of soft water over hard water. (b) list two advantages of hard water.
5.Enumerate three water pollutants you know.
WEEKEND ASSIGNMENT:
Read New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio; pages 298 - 302
PRE–READING ASSIGNMENT:
Read about carbon and its compounds.
WEEKEND ACTIVITY
(a)Describe the structure of carbon atom and its properties.(b) What are the allotropes of carbon.
WEEK 5
TOPICS: Carbon and its Compounds.
CONTENT:
I. Carbon, allotropes and their structures,
ii.Properties, Difference between diamond and graphite
iii. Combustion of carbon allotropes
SUB-TOPIC 1:CARBON, ALLOTROPES AND THEIR STRUCTURES
Carbon is a non -metal found in the group4 it occurs naturally as diamond and graphite. Also,it occurs in an impure form as cold and in the combine state as petroleum, wood and natural gases.
Atomic structure of carbon
Carbon is the sixth element in the periodic table. the nucleus its atom it composed of six proton and six neutron and surrounded by six electron;2 in the first energy level(k-shell)and four in the 2nd energy level ( L-shell).its orbital configuration is 1S22S22P2.Carbonatom has four valency electrons. Carbon atoms are able to catenate, i.e. join to one another by covalent bonds in a continuous fashion. The phenomenon is called catenation.
Allotropes of carbon
Allotropy is the existence of an element in the same physical state but indifferent forms. The various forms are called allotropes.
Carbon exhibits allotropy. Other elements that also exhibit allotropy are sulphur, Tin, Oxygen and Phosphorus. The two crystalline allotropes of carbon are: Diamond and graphite.
Diamond
Structure and Bonding
In diamond, each carbon atom is at the center of a regular tetrahedron and covalently bonded to four other atoms in a strong compact fashion. The covalent linking between the atoms is continuous to produce a single infinite tightly locked 3-dimensional giant (macro) molecule, which has a network octahedral structure see the diagram below:
The rigidity of the structure is responsible for the hardness of diamond; it is the hardest known substance. Since the covalent bonds are strong and the molecule is compact, the melting point of diamond is very high.
PHYSICAL PROPERTIES OF DIAMOND
1. Pure diamond is hard, coloureless and transparent
2. Forms octahedral crystals with high refractive index.
3. It is very hard; it has a density of 3.5gcm-3, and melting point of 36000c.
4. It does not conduct electricity, because all the four valence electrons per carbon atom are used in bonding i.e.no mobile electrons.
5. It is insoluble in any solvent.
USES OF DIAMOND
Because of its high refractive index and amazing metallic luster when cut, it is used in jewelries.
Because of its hardness, diamond is used in cutting glasses, in drilling rocks; in boring of holes; in making bearings in engines; and as an abrasive,i.e.to smoothen rough surfaces.
GRAPHITE
Structure and Bonding
In graphite, each carbon atom is covalently bonded to three other atoms to produce an infinite two-dimensional flat hexagon layer structure, which is strong and hard see the diagram above. The flat hexagonal layers in graphite are held together by the weak van der Waals attractive forces, which allow movement of the planes parallel to each other, and make the graphite to be soft and slippery. The fourth electron in the valence shell of each carbon atom in graphite is mobile, becauseit is not used in bonding, and account for its electrical conductivity.
Physical properties of graphite
Graphite form soft, black and opaque hexagonal crystals, which are greasy to feel. The softness is due to the ability of the adjacent layers to slide over one another.
It is hard;its density is 2.3gcm-3, and melts at about 35000c.
It is good conductor of heat and electricity-due to the presence of a mobile electron per carbon atom.
It is soluble in any solvent. Graphite is an example of a non –metallic conductor.it is a metalloid.
USES OF GRAPHITE
Graphite is used as a lubricant, because it is soft, in soluble in water and heat resistance.
Used as inert electrodes during electrolysis and for brushes of electric motors been a good conductor of electric current.
When mixed with clay, graphite forms lead, which is used in making lead pencils. The hardness of a pencil depends on the amount of clay in the mixture. Soft pencils contain more of graphite, while hard pencils contain more of clay.
Used in making crucible, because of its high melting point.
Used in nuclear reactors; being soft and with a high melting point.
DIFFERENCE BETWEEN DIAMOND AND GRAPHITE
DIAMOND PROPERTIES GRAPHITE PROPERTIES
Diamond is a transparent solid that sparkles when cut and polished Graphite is an opaque solid, with a metallic luster
It is octahedral in shape It is hexagonal in shape
Its density is 3.5〖3.5gcm〗^(-3) Its density is 2.3〖3.5gcm〗^(-3)
It is a poor conductor of electricity It is a good conductor of electricity
It is an inert substance but at 9000c, it burns in air to form carbon(iv) oxide and combines with fluorine It is a more reactive substance burns in air to form carbon (iv) oxide at 7000c, it also reacts with oxidizing agents to form oxides, it also reacts with fluorine and tetraoxosulphate(vi) acid
It is the hardest substance known It is one of the softest minerals known.
EVALUTION
1. Define the term allotropy.
2. What is the structure of?
(a).diamond (b).graphite.
3. Give the reason why diamond is hard, while graphite is soft.
SUB TOPIC 2: THE COMBUSTION OF CARBON ALLOTROPES
Carbon burns in limited supply of air to form carbon (II) oxide equation for the reaction is given as
2C(s) + O2(g) 2CO (g)
In excess air, complete combustion takes place and carbon(Iv) oxide is formed. Equation for the reaction is given as.
C(s) + O2 CO (g)
When charcoal is used as fuel, it burns released is used for cooking (exothermic reaction)
NOTE:Carbon occurs most abundantly both naturally as diamond and graphite and in numerous compounds including petroleum coal, natural gas among others.
EVALUATION
Carbon occurs most abundantly both naturally as _________ and ______
With two equations only, describe the combustion of carbon allotropes.
GENERAL EVALUATION
ESSAY QUESTIONS:
What do you understand by the term allotropy?
Mention two main types of alltropes of carbon.
Differentiate the two main types of allotropes of carbon with their diagrams only
In a tabular form, differentiate the two main types of alltropes of carbon.
Apart from the two main types of allotropes of carbon, mention other three more.
OBJECTIVE TEST:
1.Carbon is often deposited in the exhaust pipes of cars because of the. (a) Presence of carbon (b) Incomplete combustion of petrol
2.Destructive distillation of coal means --------- (a) heating coal in plentiful supply of air (b) heating coal in the absence of air.
3.An aqueous sodium trioxocarbonate(vi) solution is alkaline because the salt is __________ (a) fully ionized in water (b) hydrolysed in water
4.The following statements about graphite are correct except that it ____________. (a) is used as a lubricant (b) has a network structure
5. The following can be obtained directly from the destructive distillation of coal except. (a) ammonia liquor (b) producer gas
ESSAY QUESTIONS
1.What do you understand by the term allotropy?
2.Mention two main types of allotropes of carbon.
3.Differentiate the two main types of allotropes of carbon with their diagrams only
4.In a tabular form, differentiate the two main types of allotropes of carbon.
5.Mention three amorphous or non crystalline forms of carbon
WEEKEND ASSIGNMENT:
1. Read comprehensiveG.N.C Ohia, et al.
2. New School Chemistry for Senior Secondary Schools.by Ababio.
CONTENT:
I. Carbon, allotropes and their structures,
ii.Properties, Difference between diamond and graphite
iii. Combustion of carbon allotropes
SUB-TOPIC 1:CARBON, ALLOTROPES AND THEIR STRUCTURES
Carbon is a non -metal found in the group4 it occurs naturally as diamond and graphite. Also,it occurs in an impure form as cold and in the combine state as petroleum, wood and natural gases.
Atomic structure of carbon
Carbon is the sixth element in the periodic table. the nucleus its atom it composed of six proton and six neutron and surrounded by six electron;2 in the first energy level(k-shell)and four in the 2nd energy level ( L-shell).its orbital configuration is 1S22S22P2.Carbonatom has four valency electrons. Carbon atoms are able to catenate, i.e. join to one another by covalent bonds in a continuous fashion. The phenomenon is called catenation.
Allotropes of carbon
Allotropy is the existence of an element in the same physical state but indifferent forms. The various forms are called allotropes.
Carbon exhibits allotropy. Other elements that also exhibit allotropy are sulphur, Tin, Oxygen and Phosphorus. The two crystalline allotropes of carbon are: Diamond and graphite.
Diamond
Structure and Bonding
In diamond, each carbon atom is at the center of a regular tetrahedron and covalently bonded to four other atoms in a strong compact fashion. The covalent linking between the atoms is continuous to produce a single infinite tightly locked 3-dimensional giant (macro) molecule, which has a network octahedral structure see the diagram below:
The rigidity of the structure is responsible for the hardness of diamond; it is the hardest known substance. Since the covalent bonds are strong and the molecule is compact, the melting point of diamond is very high.
PHYSICAL PROPERTIES OF DIAMOND
1. Pure diamond is hard, coloureless and transparent
2. Forms octahedral crystals with high refractive index.
3. It is very hard; it has a density of 3.5gcm-3, and melting point of 36000c.
4. It does not conduct electricity, because all the four valence electrons per carbon atom are used in bonding i.e.no mobile electrons.
5. It is insoluble in any solvent.
USES OF DIAMOND
Because of its high refractive index and amazing metallic luster when cut, it is used in jewelries.
Because of its hardness, diamond is used in cutting glasses, in drilling rocks; in boring of holes; in making bearings in engines; and as an abrasive,i.e.to smoothen rough surfaces.
GRAPHITE
Structure and Bonding
In graphite, each carbon atom is covalently bonded to three other atoms to produce an infinite two-dimensional flat hexagon layer structure, which is strong and hard see the diagram above. The flat hexagonal layers in graphite are held together by the weak van der Waals attractive forces, which allow movement of the planes parallel to each other, and make the graphite to be soft and slippery. The fourth electron in the valence shell of each carbon atom in graphite is mobile, becauseit is not used in bonding, and account for its electrical conductivity.
Physical properties of graphite
Graphite form soft, black and opaque hexagonal crystals, which are greasy to feel. The softness is due to the ability of the adjacent layers to slide over one another.
It is hard;its density is 2.3gcm-3, and melts at about 35000c.
It is good conductor of heat and electricity-due to the presence of a mobile electron per carbon atom.
It is soluble in any solvent. Graphite is an example of a non –metallic conductor.it is a metalloid.
USES OF GRAPHITE
Graphite is used as a lubricant, because it is soft, in soluble in water and heat resistance.
Used as inert electrodes during electrolysis and for brushes of electric motors been a good conductor of electric current.
When mixed with clay, graphite forms lead, which is used in making lead pencils. The hardness of a pencil depends on the amount of clay in the mixture. Soft pencils contain more of graphite, while hard pencils contain more of clay.
Used in making crucible, because of its high melting point.
Used in nuclear reactors; being soft and with a high melting point.
DIFFERENCE BETWEEN DIAMOND AND GRAPHITE
DIAMOND PROPERTIES GRAPHITE PROPERTIES
Diamond is a transparent solid that sparkles when cut and polished Graphite is an opaque solid, with a metallic luster
It is octahedral in shape It is hexagonal in shape
Its density is 3.5〖3.5gcm〗^(-3) Its density is 2.3〖3.5gcm〗^(-3)
It is a poor conductor of electricity It is a good conductor of electricity
It is an inert substance but at 9000c, it burns in air to form carbon(iv) oxide and combines with fluorine It is a more reactive substance burns in air to form carbon (iv) oxide at 7000c, it also reacts with oxidizing agents to form oxides, it also reacts with fluorine and tetraoxosulphate(vi) acid
It is the hardest substance known It is one of the softest minerals known.
EVALUTION
1. Define the term allotropy.
2. What is the structure of?
(a).diamond (b).graphite.
3. Give the reason why diamond is hard, while graphite is soft.
SUB TOPIC 2: THE COMBUSTION OF CARBON ALLOTROPES
Carbon burns in limited supply of air to form carbon (II) oxide equation for the reaction is given as
2C(s) + O2(g) 2CO (g)
In excess air, complete combustion takes place and carbon(Iv) oxide is formed. Equation for the reaction is given as.
C(s) + O2 CO (g)
When charcoal is used as fuel, it burns released is used for cooking (exothermic reaction)
NOTE:Carbon occurs most abundantly both naturally as diamond and graphite and in numerous compounds including petroleum coal, natural gas among others.
EVALUATION
Carbon occurs most abundantly both naturally as _________ and ______
With two equations only, describe the combustion of carbon allotropes.
GENERAL EVALUATION
ESSAY QUESTIONS:
What do you understand by the term allotropy?
Mention two main types of alltropes of carbon.
Differentiate the two main types of allotropes of carbon with their diagrams only
In a tabular form, differentiate the two main types of alltropes of carbon.
Apart from the two main types of allotropes of carbon, mention other three more.
OBJECTIVE TEST:
1.Carbon is often deposited in the exhaust pipes of cars because of the. (a) Presence of carbon (b) Incomplete combustion of petrol
2.Destructive distillation of coal means --------- (a) heating coal in plentiful supply of air (b) heating coal in the absence of air.
3.An aqueous sodium trioxocarbonate(vi) solution is alkaline because the salt is __________ (a) fully ionized in water (b) hydrolysed in water
4.The following statements about graphite are correct except that it ____________. (a) is used as a lubricant (b) has a network structure
5. The following can be obtained directly from the destructive distillation of coal except. (a) ammonia liquor (b) producer gas
ESSAY QUESTIONS
1.What do you understand by the term allotropy?
2.Mention two main types of allotropes of carbon.
3.Differentiate the two main types of allotropes of carbon with their diagrams only
4.In a tabular form, differentiate the two main types of allotropes of carbon.
5.Mention three amorphous or non crystalline forms of carbon
WEEKEND ASSIGNMENT:
1. Read comprehensiveG.N.C Ohia, et al.
2. New School Chemistry for Senior Secondary Schools.by Ababio.
WEEK 6
TOPIC: CARBON AND ITS COMPOUNDS
CONTENT: 1. Coal and types of coal
2. Destructive distillation of coal
3. Coke: Coal and types of coal
Sub-topic 1: Coal and types of coal
COAL: This is one the two most principal sources of fuel and energy, the other being petroleum. Coal was found as a result of complex chemical and physical changes when the remains of forest were buried under the earth millions of years ago under great pressure in the absence of air.
Coal is found in great abundance in very many parts of the world including Nigeria. Coal is a complex mixture of hydrocarbons (compounds of carbon and hydrogen) and other organic and inorganic compounds containing small amounts of nitrogen, sulphur and phosphorus as impurities.
Types of Coal
Coal is derived from wood; it naturally contains a lot of carbon. There are four main types of coal, arising from the progressive variation in their carbon content. They are:
Peat-like coal: contains about 60% of carbon.
Lignite coal: contains about 70% of carbon.
Bituminous coal: contains about 85% of carbon. This is the type that is mostly used for our everyday domestic application.
Anthracite coal: contains about 94% of carbon.
The carbon content of each type of coal reflects its rank or degree of classification. Based on carbon content, the different types of coals are put into ranks as follows: Peak Lignite Bituminous Anthracite
Coal is used mainly as a fuel to generate power for station engines, factories and electric parts. It is also used for making various chemicals.
EVALUATION
What is Coal?
Mention four types of coal and two uses of coal.
Sub-topic 2: Destructive distillation of coal and uses of the products
Destructive distillation of coal involves heating of coal to a very high temperature (600---1200o C ) in the absence of air. During the process, coal decomposes to give coal gas, coal tar, ammoniacal liquor and coke as the main products.
Coal heat coal gas + coal tar + ammoniacal liquor + coke
The process is also known as industrial distillation of coal. The destructive distillation of coal can be carried in the laboratory using the set up below.
Uses of product of destructive distillation of coal
Coal gas: Coal gas is a gaseous mixture of hydrogen, methane, carbon (ii) oxide and small amount of ethane, hydrogen sulphide and sulphur(iv)oxide. The main use of coal gas is as fuel. It is cleaner and more efficient than coal and solid or liquid fuel.
Coal tar: Coal tar, a thick brownish-black liquid, is a mixture of many organic chemicals including benzene, toluene, phenol, naphthalene and anthracene. The components can be separated by fractional distillation and are used for the manufacture of commercial products including drugs, dye, paints, insecticides, explosives, etc.
Ammoniacal liquor: This an aqueuous solution containing mainly ammonia and is used in the manufacture of ammonium tetraoxosulphate(iv), (NH4)2SO4 .
Coke: Coke is non-volatile residue which contains about 90% of amorphous carbon and is chemically similar to hard coal. Coke is used in the manufacture of carbide, as a fuel and as a reducing agent in the extracting of metals. Coke is used to make producer gas and water gas through a process called gasification.
EVALUATION
Highlight 4 main products of destructive distillation of coal. State their uses.
Explain briefly, how destructive distillation of coal is obtained.
Uses of Coke
It is used as fuel both industrially and domestically
It is used to manufacture carbide used in production of ethyne.
It is a reducing agent in the extraction of metals from their ores.
It is used in the production of graphite.
Gasification of Coke: Gasification of gas is the conversion of coke to gas. This can be done in two ways:
By combining of coke with oxygen in the air to give producer gas.
By combination of coke with steam to give water gas.
GASIFICATION OF COKE
Producer gas: This is a mixture of one-third of carbon(II)oxide and two-thirds nitrogen by volume. It is obtained by heating coke in a furnace in a limited. This is achieved by passing air through red hot coke. During the process, coke is oxidized to carbon (IV) oxide which is subsequently reduced by the hot coke to carbon (II) oxide, a combustible gas. The process can be represented by the following equations.
C(s) + O2(g) CO2 + heat
CO(g + C 2CO2
Or
O2 + 4N2 + 2C 4N2(s) + 2CO(s) + heat
Uses
Producer gas is used as fuel in furnaces, retorts and limekilns.
It is used as a source of nitrogen for the manufacture of ammonia.
Water gas
Water gas is produced by passing steam through hot coke at 1000oC. This results in reduction of the steam; carbon (II) oxide and hydrogen are formed. Water gas is mixture containing hydrogen and carbon (II) oxide in equal volume.
C(s) + H2O(l) CO(s) + H2
Water gas has a high calorific value because both carbon (II) 0xide and hydrogen are combustible.
Uses
Water gas is used as a fuel
It is used as a source of hydrogen and other organic compounds.
EVALUATION
Differentiate between water gas and producer gas
What is gasification of coke
GENERAL EVALUATION
OBJECTIVE TEST
Water gas is a mixture of A. CO2 and H2 B. CO2 and H2O C. CO2 D. CO and H2
The following can be obtained directly from the destructive distillation of coal except: A. ammoniacal liquor B. coke C. Producer gas D. Coal tar E. coal gas
Destructive distillation of coal means A. heating coal in plentiful supply of air B. heating coal in air to produce H2O and CO2
The liquid product from the destructive distillation of coal is A. ammoniacal liquor B. Coal fume C. Dyestuff D. coal plasma
Producer gas is with a low heating power because it contains more A.CO2 than O2 B. nitrogen than carbon (II) oxide C. CO2 than nitrogen D. nitrogen than O2
ESSAY QUESTIONS
1. Write short note on the following:
Destructive distillation of coal.
Coke
Ammoniacal liquor
Coal tar
CONTENT: 1. Coal and types of coal
2. Destructive distillation of coal
3. Coke: Coal and types of coal
Sub-topic 1: Coal and types of coal
COAL: This is one the two most principal sources of fuel and energy, the other being petroleum. Coal was found as a result of complex chemical and physical changes when the remains of forest were buried under the earth millions of years ago under great pressure in the absence of air.
Coal is found in great abundance in very many parts of the world including Nigeria. Coal is a complex mixture of hydrocarbons (compounds of carbon and hydrogen) and other organic and inorganic compounds containing small amounts of nitrogen, sulphur and phosphorus as impurities.
Types of Coal
Coal is derived from wood; it naturally contains a lot of carbon. There are four main types of coal, arising from the progressive variation in their carbon content. They are:
Peat-like coal: contains about 60% of carbon.
Lignite coal: contains about 70% of carbon.
Bituminous coal: contains about 85% of carbon. This is the type that is mostly used for our everyday domestic application.
Anthracite coal: contains about 94% of carbon.
The carbon content of each type of coal reflects its rank or degree of classification. Based on carbon content, the different types of coals are put into ranks as follows: Peak Lignite Bituminous Anthracite
Coal is used mainly as a fuel to generate power for station engines, factories and electric parts. It is also used for making various chemicals.
EVALUATION
What is Coal?
Mention four types of coal and two uses of coal.
Sub-topic 2: Destructive distillation of coal and uses of the products
Destructive distillation of coal involves heating of coal to a very high temperature (600---1200o C ) in the absence of air. During the process, coal decomposes to give coal gas, coal tar, ammoniacal liquor and coke as the main products.
Coal heat coal gas + coal tar + ammoniacal liquor + coke
The process is also known as industrial distillation of coal. The destructive distillation of coal can be carried in the laboratory using the set up below.
Uses of product of destructive distillation of coal
Coal gas: Coal gas is a gaseous mixture of hydrogen, methane, carbon (ii) oxide and small amount of ethane, hydrogen sulphide and sulphur(iv)oxide. The main use of coal gas is as fuel. It is cleaner and more efficient than coal and solid or liquid fuel.
Coal tar: Coal tar, a thick brownish-black liquid, is a mixture of many organic chemicals including benzene, toluene, phenol, naphthalene and anthracene. The components can be separated by fractional distillation and are used for the manufacture of commercial products including drugs, dye, paints, insecticides, explosives, etc.
Ammoniacal liquor: This an aqueuous solution containing mainly ammonia and is used in the manufacture of ammonium tetraoxosulphate(iv), (NH4)2SO4 .
Coke: Coke is non-volatile residue which contains about 90% of amorphous carbon and is chemically similar to hard coal. Coke is used in the manufacture of carbide, as a fuel and as a reducing agent in the extracting of metals. Coke is used to make producer gas and water gas through a process called gasification.
EVALUATION
Highlight 4 main products of destructive distillation of coal. State their uses.
Explain briefly, how destructive distillation of coal is obtained.
Uses of Coke
It is used as fuel both industrially and domestically
It is used to manufacture carbide used in production of ethyne.
It is a reducing agent in the extraction of metals from their ores.
It is used in the production of graphite.
Gasification of Coke: Gasification of gas is the conversion of coke to gas. This can be done in two ways:
By combining of coke with oxygen in the air to give producer gas.
By combination of coke with steam to give water gas.
GASIFICATION OF COKE
Producer gas: This is a mixture of one-third of carbon(II)oxide and two-thirds nitrogen by volume. It is obtained by heating coke in a furnace in a limited. This is achieved by passing air through red hot coke. During the process, coke is oxidized to carbon (IV) oxide which is subsequently reduced by the hot coke to carbon (II) oxide, a combustible gas. The process can be represented by the following equations.
C(s) + O2(g) CO2 + heat
CO(g + C 2CO2
Or
O2 + 4N2 + 2C 4N2(s) + 2CO(s) + heat
Uses
Producer gas is used as fuel in furnaces, retorts and limekilns.
It is used as a source of nitrogen for the manufacture of ammonia.
Water gas
Water gas is produced by passing steam through hot coke at 1000oC. This results in reduction of the steam; carbon (II) oxide and hydrogen are formed. Water gas is mixture containing hydrogen and carbon (II) oxide in equal volume.
C(s) + H2O(l) CO(s) + H2
Water gas has a high calorific value because both carbon (II) 0xide and hydrogen are combustible.
Uses
Water gas is used as a fuel
It is used as a source of hydrogen and other organic compounds.
EVALUATION
Differentiate between water gas and producer gas
What is gasification of coke
GENERAL EVALUATION
OBJECTIVE TEST
Water gas is a mixture of A. CO2 and H2 B. CO2 and H2O C. CO2 D. CO and H2
The following can be obtained directly from the destructive distillation of coal except: A. ammoniacal liquor B. coke C. Producer gas D. Coal tar E. coal gas
Destructive distillation of coal means A. heating coal in plentiful supply of air B. heating coal in air to produce H2O and CO2
The liquid product from the destructive distillation of coal is A. ammoniacal liquor B. Coal fume C. Dyestuff D. coal plasma
Producer gas is with a low heating power because it contains more A.CO2 than O2 B. nitrogen than carbon (II) oxide C. CO2 than nitrogen D. nitrogen than O2
ESSAY QUESTIONS
1. Write short note on the following:
Destructive distillation of coal.
Coke
Ammoniacal liquor
Coal tar
WEEK 7
TOPIC: CARBON AND ITS COMPOUND
CONTENT:
(1) Carbon (ii) Oxide (CO), Carbon (IV) oxide (CO2) their preparations, properties and uses, synthetic gas.
(2) Metallic trioxocarbonates; occurrences, preparation and uses.
(3) Trioxocarbonate (iv) acid: preparation, properties and uses
(4) Test for carbon ion
SUB TOPIC 1: Carbon (ii) oxide and carbon (iv) oxide –their preparation and uses, synthetic gas.
FORMATION / PREPARATION OF CARBON (IV)OXIDE (CO2)
In excess air, there is incomplete combustion; carbon (iv) oxide is produce but in the limited supply of air carbon normally react with oxygen to produce carbon(ii) oxide. The equation of reaction is given below for the two reactions.
C_s + O_(2(g)) CO2(g) + heat
2C(s) + O_(2(g)) 2CO(g) + heat
Other methods of preparation of CO2 are:
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
The decomposition of trioxocarbonates(iv)salts [except those of Sodium and Potassium] or hydrogen trioxcarbonate(iv) salts, by strong heat e.g
CaCO3(s) CaO(s) + CO2
2NaHCO3(s) Na2CO3(s) + H2O +CO2(g)
(iii) Action of dilute mineral acid on trioxocarbonate(iv) or hydrogentrioxocarbonate(iv)salt e.g
Na2CO3(s) + 2HCl(aq) 2 NaCl(aq) + H2O(l) + CO2(g)
KHCO3(s) + HNO3(aq) KNO3(aq) + H2O(l) + 2CO2
(iv) The fermentation of glucose by enzyme (zymase)
C6H12O6(ag) 2C2H5OH(aq) + 2CO2(g)
LABORATORY PREPARATION OF CO2 GAS
The equation for the reaction is given as shown below
CaCO3(s) + HCl(aq) CaCl2(aq) + H2O + CO2(g)
Pure and dry CO2 is obtained by passing the gas through a solution of potassium hydrogentrioxocarbonate(iv) [KHCO3] to remove the acid impurities, hydrogen chloride and then, through conc.H_2 〖SO〗_4 (or fused CaCl2to dry the gas. It is then collected by downwards delivery, being denser than air as in the diagram above.
PHYSICAL PROPERPIES OF CO2(g)
It is a colourless and odourless gas
It does not support combustion
It is heavier than air.
It is easily liquefied at low temperature with pressure higher than 5 atmospheres.
CHEMICAL PROPERTIES OF CO2(g)
It dissolve in water to give trioxocarbonate(iv) acid [H2CO](aq
)H2O + CO2 H2CO3(aq) 2H+ + CO32-(aq)
-∴ CO2 is an acid anhydride of H2CO3
It turns damp blue litmus paper red
It neutralizes the base [ NaOH, KOH] to give salt and water only.
CO2 + 2NaOH(aq) 〖Na〗_2 〖CO〗_(3(aq)) + H_2 O
When a large excess of the gas is used an acid salt is formed as shown the equation above;
〖Na〗_(2 ) 〖CO〗_(3(aq))+ H2O + CO2(ag) 2NaHCO3(aq)
It acts as an oxidizing agents as shown in the reaction below. (a) C(s) + C+4O2(g) 2CO+2(g)
(b) 2Mg0(s) + CO2+4(g) 2Mg+2O(s) + C(s)
In this reaction, magnesium is oxidized to its oxide while CO2 is reduced to carbon.
It reacts with lime water to form Ca(OH)2, the equation is
CO2(g) + Ca(OH)2 CaCO3(s) + H20(l)
When it lasted for long inside lime water Ca(OH)2, the equation is
CaCO3(s) +H20(l)+ CO2(g) Ca[HCO3]2(aq)colourless
These equations above are the laboratory chemical test for the presence of CO2 gas.
Uses of CO2
It is used in fire extinguishers because it is heavier than air and it does not support combustion.
It is used in the production of aerated drinks such as Coca-Cola, 7-Up and Pepsi-Cola.
It is as effervescent in certain health salts such as Andrew Liver salt or Epson salt.
It is mixed with tartaric acid and corn starch to form baking powder (NaHCO3); causing bread to rise.
It is used in the production of Na2CO3 by Solvay process.
It is necessary for photosynthesis. The dissolved CO2 gas in sea-water provides sea plants with food for photosynthesis.
Solid CO2 is called Dry ice. It is used as a refrigerant in preserving food stuff. It is used as a coolant in nuclear reactor. It is called dry ice because it sublimes readily, without forming a liquid.
Dry ice: Advantages over popular ice
Dry produces a greater cooling effect thanequal mass of the common ice [ice block], because dry ice can provide a temperature of -790C [194k]
Again dry ice on warming sublimes [changes from solid to gas] without leaving any liquid; unlike ice which melts to produce water.
CAUTION: Never handle solid CO2, dry ice, with bare hands; it causes painful blisters similar to those caused by hot objects.
CARBON (II) OXIDE
LABORATORY PREPARATION OF CO [in the fume cupboard]
Three methods can be used to prepare CO in the lab and they are as follows;
Ethanedioc acid crystals [H2C2O4.2H2O]
The equation for the reaction is given as shown below;
H2C2O4.2H2O(s) decomposed 3H2O(l) + CO(g) + CO2(g)
Note: That conc. H2SO4 is a drying agent, it is there to remove the elements of water while KOH removes CO2(g)
CO2(g) + 2KOH(aq) K2CO3(aq) + H2O(l)
2a. Sodium Methanoate crystals
2HCOONa(s) + H2SO4 (aq) Na2SO4(aq) + 2H2O + 2CO(g)
b. Sodium methanoate.
OR
HCOOH(l)H2SO4/(-H2 O) CO(g)
Show that H2SO4/(-H2 O) removes/a dehydrating agent
3. Reduction of CO2(g) to CO as shown below
CO2(g) + C(s) 2CO(g)
PHYSICAL PROPERTIES OF CO
It is colourless, odourless and tasteless gas.
It is slightly lighter than air.
It is only slightly soluble in water, but insoluble in alkalis.
It is soluble in ammonical solution of copper (I) chloride.
It is a poisonous gas, hence, prepared in fume cupboard.
CHEMICAL PROPERTIES AND USES OF CO
It is used as fuel because it supports combustion.
It is a neutral gas therefore; it does not have any action on the Litmus paper.
It is a useful reducing agent because it is readily reduce to CO2(g) e.g.
CO(g) + H2O CO2(g) + H2(g)
CO(g) + CUO(s) CU(s) + CO2(g)
3CO(g) + Fe2O3(s) 2Fe(s) + 3 CO2(g)
CO(g) + PbO(s) Pb(s) + CO2(g)
Note: The product of combustion or oxidation of CO is CO2; confirmed by its ability to turn lime water milky.
Ni(s) + 4CO(g) Ni(CO)4(s)
At 1800C, nickel carbonyl decomposes to give carbon(II) oxide
Ni(CO)4(s) Ni(s) + 4CO(g)
Ni(CO)4(s)nickel carbonyl
It combines with chlorine, using finely divided carbon as catalyst to form carbonyl chloride, COCl2[Phosgene]; a poisonous liquid
CO(g) + Cl2(g) COCl2
EVALUATION
List the two reactants for the laboratory preparation of carbon(IV) oxide
Draw a labelled diagram for the laboratory preparation of dry sample of Carbon(IV) oxide.
Describe the laboratory test for CO2
Describe what will happen when CO2 is passed into water Ca(OH)2(aq) for a while then in excess
Describe 2 methods of laboratory preparation of CO(g)
SUB TOPIC 2: SYNTHETIC GAS
Like water gas, synthetic gas is a mixture of CO and hydrogen. It is obtained by passing natural gas [Methane] over steam or air in the presence of Nickels as the catalysts to give a mixture of CO and hydrogen
CH2+(g) + H2O(g) Ni 9000C CO(g) + 3H2(g)
2CH4(g) + O2(g) Ni 9000C 2Co(g) + 4H2(g)
SEPARATION OF THE CONSTITUENTS OF PRODUCER GAS AND WATER
Producer gas is a mixture of CO and Nitrogen, while water gas is a mixture of CO2 and hydrogen.
Note: A fuel is any substance that burns in air or oxygen to produce heat and light. Producer gas and water gas are examples fuels, solid fuels, wood, coal and coke
Liquid fuels e.g. producer gas, kerosene, alcohol or methylated spirit
Gaseous fuels- e.g. producer gas, water gas, coal gas, natural gas paraffin gas and synthetic gas.
Human fuels e.g. food items in the form of fat and oil, protein, starch and sugar
Atomic fuel e.g. uranium
EVALUATION
What is meant by fuel?
State the components of each of the following (a) water gas (b) Producer gas (c) coal gas (d) synthesis gas
SUB-TOPIC 3:Metallic trioxocarbonates, occurrences, preparation and uses and trioxocarbonates(IV) acid preparation, properties and uses, Test for carbonate ion.
METALLIC TRIOXOCARBONATE (IV) SALTS C032-
PREPARATION OF INSOLUBLE CO2-3
All trioxocarbonate(iv) salts are insoluble in water except soluble. Hence, they are prepared by double decomposition method, using aqueous NaCO3 e.g
Na2CO3(aq) + CuSO4(aq) CUCO3(s) + Na2SO4(aq)
Na2CO3(aq)+ Zncl2(aq) ZnCO3(s) + 2NaCl(aq
White
METHOD 2: Ca[OH]2(aq) + CO2(g) CaCO3(s) + H2O(l)
PROPERTIES OF SALTS
All trioxocarbonate(iv) salts are insoluble in water, except those of Na, K and NH4 which are soluble.
They dissolve in water to produce alkaline solutions. This is because they are salts of strong bases and weak acid, hence, they hydrolysed in water to produce alkaline
Solutions’
e.g K2CO3(s) + 2H2O 2KOH(aq) + H2CO3(aq)
3. All trioxocarbonate(IV) salts except those of potassium and Sodium, decompose on heating, to liberate CO2(g)
e.g. ZnCO3(s) ZnO(s) + Co2(g)
(NH4)2CO3(s) 2NH3(g) + H2O(g) + Co2(g)
Note: Na2CO3 and K2CO3 are not affected by heating, to liberate carbon (iv) oxide e.g
ZnCO3(s) + 2HCl(aq) ZnCl2(aq) + H2O(l) + CO2(g)
Ionically: CO3(s)2-+ 2H+(aq H2O(l) + CO2(g)
CHEMICAL TESTS FOR CO32- SALTS
Test on liquid on Solid (dry test)---------(a)
Small solid sample of salt is put in a test tube and few drops of dilute hydrochloric acid was added---- effervescence occur, then an odourless colourless gas was given off which in turn moist blue litmus paper slightly red and turns lime water. Gas is CO2(g)
Test (wet test) --------(b)
Barium chloride solution was added to few drops of solution of salt in test tube. A white precipitate was formed
CO2-3(ag) + BaCl2(aq) BaCO3(s) + 2Cl-(aq)
The precipitate is soluble in dilute HCl, to give a colourless solution.
BaCO3(s)+ 2HCl(aq) BaCl2(aq)+ H2CO3(aq)
TRIOXOCARBONATE (IV) ACID
Trioxocarbonate(IV) [carbonic acid], H2 CO3 is a very weak diabasic acid. It is obtained when carbon (iv) oxide dissolves in water. It is unsuitable; hence never isolated.
CO2(g) + H2O H2CO3(aq) 2H+(aq) + CO2-3(aq)
The acid forms both the normal and acid salts; i.e the acid ionizes into two stages;
H2CO3(aq) H2CO3(aq) H+(aq) + HCO-3(aq)
HCO-3(aq) H+(aq) + CO2-3(aq)
Uses of trioxocarbonate (IV) salts
Na2CO3 is used in softening hard water, in making soap and glass, and as an alkali in acid-base titration.
CaCO3 is used in making quick lime, cement and glass; in agriculture [in liming the soil – to reduce acidity]
EVALUATION
Describe the laboratory preparation of metallic trioxocarbonate(iv) salts
List two properties of trioxocarbonate(iv) salts
Give one method for preparation of trioxocarbonate(iv) acid
GENERAL EVALUATION
OBJECTIVE TEST
Where else is CO2 found in Free State apart from the atmosphere. A. carbonated trees B. dissolved form in water C. in corals D. in limestone region
All are decomposed by heat except A. BaCO3 B. CuCO3 C.AgCO3 D. ZnCO3
Which of the following trioxocarbonates (iv) are not decomposed by heat A. Calcium and Sodium trioxocarbonate (iv) C. Potassium and Zinc trioxocarbonate (iv) D. Zinc and Potassium trioxocarbonate (iv) E. Sodium and potassium trioxocarbonate (iv)
It is dangerous to stay in a badly ventilated room which has a charcoal fire because of the presence of A.CO2 B. CO C. Hydrogen D. Sulpur E. Methane
One of these gases is heavier than air and do not support combustion. A. CO B. CO2 C. H2O D. N2O
ESSAY QUESTIONS
Name one process which. (i) removes carbon (ii) fixes atmospheric nitrogen as trionitrate (iii) oxide from the atmosphere (iv) in the soil
Describe one of the method of Laboratary preparation of Carbon(II)oxide
Describe one of the method of laboratory preparation of (CO2(g)) Carbon (iv) oxide
Explain fully how CO2(g) can be detected in the laboratory.
How can you differentiate trioxocarbonate (iv) salt and trioxocarbonate (iv) acid with at least two points.
WEEKEND ASSIGNMENT:
Read comprehensive certificate chemistry 2nd edition by G.N.C Ohia, G.I. Amasiatu, J.O. Ajagbe, G.O Ojokuku and U. Mohammed pages 95-102
PRE READING ASSIGNMENT
Read hydrocarbon ant its main classes, crude oil and natural gas and importance of hydrocarbons.
WEEKEND ACTIVITY:
Explain in detail, the laboratory preparation of (i) CO (g) (ii) CO2(g) (iii) CO2-3 salts (iv)HCO3respectively.
REFERENCE TEXTS:
G.N.C Ohia, G.I. Amasiatu, J.O. Ababa, G.O Ojokuku and U. Mohammed.
Revised Edition Understanding Chemistry for schools and colleges by Godwin O. Ojokuku
CONTENT:
(1) Carbon (ii) Oxide (CO), Carbon (IV) oxide (CO2) their preparations, properties and uses, synthetic gas.
(2) Metallic trioxocarbonates; occurrences, preparation and uses.
(3) Trioxocarbonate (iv) acid: preparation, properties and uses
(4) Test for carbon ion
SUB TOPIC 1: Carbon (ii) oxide and carbon (iv) oxide –their preparation and uses, synthetic gas.
FORMATION / PREPARATION OF CARBON (IV)OXIDE (CO2)
In excess air, there is incomplete combustion; carbon (iv) oxide is produce but in the limited supply of air carbon normally react with oxygen to produce carbon(ii) oxide. The equation of reaction is given below for the two reactions.
C_s + O_(2(g)) CO2(g) + heat
2C(s) + O_(2(g)) 2CO(g) + heat
Other methods of preparation of CO2 are:
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
The decomposition of trioxocarbonates(iv)salts [except those of Sodium and Potassium] or hydrogen trioxcarbonate(iv) salts, by strong heat e.g
CaCO3(s) CaO(s) + CO2
2NaHCO3(s) Na2CO3(s) + H2O +CO2(g)
(iii) Action of dilute mineral acid on trioxocarbonate(iv) or hydrogentrioxocarbonate(iv)salt e.g
Na2CO3(s) + 2HCl(aq) 2 NaCl(aq) + H2O(l) + CO2(g)
KHCO3(s) + HNO3(aq) KNO3(aq) + H2O(l) + 2CO2
(iv) The fermentation of glucose by enzyme (zymase)
C6H12O6(ag) 2C2H5OH(aq) + 2CO2(g)
LABORATORY PREPARATION OF CO2 GAS
The equation for the reaction is given as shown below
CaCO3(s) + HCl(aq) CaCl2(aq) + H2O + CO2(g)
Pure and dry CO2 is obtained by passing the gas through a solution of potassium hydrogentrioxocarbonate(iv) [KHCO3] to remove the acid impurities, hydrogen chloride and then, through conc.H_2 〖SO〗_4 (or fused CaCl2to dry the gas. It is then collected by downwards delivery, being denser than air as in the diagram above.
PHYSICAL PROPERPIES OF CO2(g)
It is a colourless and odourless gas
It does not support combustion
It is heavier than air.
It is easily liquefied at low temperature with pressure higher than 5 atmospheres.
CHEMICAL PROPERTIES OF CO2(g)
It dissolve in water to give trioxocarbonate(iv) acid [H2CO](aq
)H2O + CO2 H2CO3(aq) 2H+ + CO32-(aq)
-∴ CO2 is an acid anhydride of H2CO3
It turns damp blue litmus paper red
It neutralizes the base [ NaOH, KOH] to give salt and water only.
CO2 + 2NaOH(aq) 〖Na〗_2 〖CO〗_(3(aq)) + H_2 O
When a large excess of the gas is used an acid salt is formed as shown the equation above;
〖Na〗_(2 ) 〖CO〗_(3(aq))+ H2O + CO2(ag) 2NaHCO3(aq)
It acts as an oxidizing agents as shown in the reaction below. (a) C(s) + C+4O2(g) 2CO+2(g)
(b) 2Mg0(s) + CO2+4(g) 2Mg+2O(s) + C(s)
In this reaction, magnesium is oxidized to its oxide while CO2 is reduced to carbon.
It reacts with lime water to form Ca(OH)2, the equation is
CO2(g) + Ca(OH)2 CaCO3(s) + H20(l)
When it lasted for long inside lime water Ca(OH)2, the equation is
CaCO3(s) +H20(l)+ CO2(g) Ca[HCO3]2(aq)colourless
These equations above are the laboratory chemical test for the presence of CO2 gas.
Uses of CO2
It is used in fire extinguishers because it is heavier than air and it does not support combustion.
It is used in the production of aerated drinks such as Coca-Cola, 7-Up and Pepsi-Cola.
It is as effervescent in certain health salts such as Andrew Liver salt or Epson salt.
It is mixed with tartaric acid and corn starch to form baking powder (NaHCO3); causing bread to rise.
It is used in the production of Na2CO3 by Solvay process.
It is necessary for photosynthesis. The dissolved CO2 gas in sea-water provides sea plants with food for photosynthesis.
Solid CO2 is called Dry ice. It is used as a refrigerant in preserving food stuff. It is used as a coolant in nuclear reactor. It is called dry ice because it sublimes readily, without forming a liquid.
Dry ice: Advantages over popular ice
Dry produces a greater cooling effect thanequal mass of the common ice [ice block], because dry ice can provide a temperature of -790C [194k]
Again dry ice on warming sublimes [changes from solid to gas] without leaving any liquid; unlike ice which melts to produce water.
CAUTION: Never handle solid CO2, dry ice, with bare hands; it causes painful blisters similar to those caused by hot objects.
CARBON (II) OXIDE
LABORATORY PREPARATION OF CO [in the fume cupboard]
Three methods can be used to prepare CO in the lab and they are as follows;
Ethanedioc acid crystals [H2C2O4.2H2O]
The equation for the reaction is given as shown below;
H2C2O4.2H2O(s) decomposed 3H2O(l) + CO(g) + CO2(g)
Note: That conc. H2SO4 is a drying agent, it is there to remove the elements of water while KOH removes CO2(g)
CO2(g) + 2KOH(aq) K2CO3(aq) + H2O(l)
2a. Sodium Methanoate crystals
2HCOONa(s) + H2SO4 (aq) Na2SO4(aq) + 2H2O + 2CO(g)
b. Sodium methanoate.
OR
HCOOH(l)H2SO4/(-H2 O) CO(g)
Show that H2SO4/(-H2 O) removes/a dehydrating agent
3. Reduction of CO2(g) to CO as shown below
CO2(g) + C(s) 2CO(g)
PHYSICAL PROPERTIES OF CO
It is colourless, odourless and tasteless gas.
It is slightly lighter than air.
It is only slightly soluble in water, but insoluble in alkalis.
It is soluble in ammonical solution of copper (I) chloride.
It is a poisonous gas, hence, prepared in fume cupboard.
CHEMICAL PROPERTIES AND USES OF CO
It is used as fuel because it supports combustion.
It is a neutral gas therefore; it does not have any action on the Litmus paper.
It is a useful reducing agent because it is readily reduce to CO2(g) e.g.
CO(g) + H2O CO2(g) + H2(g)
CO(g) + CUO(s) CU(s) + CO2(g)
3CO(g) + Fe2O3(s) 2Fe(s) + 3 CO2(g)
CO(g) + PbO(s) Pb(s) + CO2(g)
Note: The product of combustion or oxidation of CO is CO2; confirmed by its ability to turn lime water milky.
Ni(s) + 4CO(g) Ni(CO)4(s)
At 1800C, nickel carbonyl decomposes to give carbon(II) oxide
Ni(CO)4(s) Ni(s) + 4CO(g)
Ni(CO)4(s)nickel carbonyl
It combines with chlorine, using finely divided carbon as catalyst to form carbonyl chloride, COCl2[Phosgene]; a poisonous liquid
CO(g) + Cl2(g) COCl2
EVALUATION
List the two reactants for the laboratory preparation of carbon(IV) oxide
Draw a labelled diagram for the laboratory preparation of dry sample of Carbon(IV) oxide.
Describe the laboratory test for CO2
Describe what will happen when CO2 is passed into water Ca(OH)2(aq) for a while then in excess
Describe 2 methods of laboratory preparation of CO(g)
SUB TOPIC 2: SYNTHETIC GAS
Like water gas, synthetic gas is a mixture of CO and hydrogen. It is obtained by passing natural gas [Methane] over steam or air in the presence of Nickels as the catalysts to give a mixture of CO and hydrogen
CH2+(g) + H2O(g) Ni 9000C CO(g) + 3H2(g)
2CH4(g) + O2(g) Ni 9000C 2Co(g) + 4H2(g)
SEPARATION OF THE CONSTITUENTS OF PRODUCER GAS AND WATER
Producer gas is a mixture of CO and Nitrogen, while water gas is a mixture of CO2 and hydrogen.
Note: A fuel is any substance that burns in air or oxygen to produce heat and light. Producer gas and water gas are examples fuels, solid fuels, wood, coal and coke
Liquid fuels e.g. producer gas, kerosene, alcohol or methylated spirit
Gaseous fuels- e.g. producer gas, water gas, coal gas, natural gas paraffin gas and synthetic gas.
Human fuels e.g. food items in the form of fat and oil, protein, starch and sugar
Atomic fuel e.g. uranium
EVALUATION
What is meant by fuel?
State the components of each of the following (a) water gas (b) Producer gas (c) coal gas (d) synthesis gas
SUB-TOPIC 3:Metallic trioxocarbonates, occurrences, preparation and uses and trioxocarbonates(IV) acid preparation, properties and uses, Test for carbonate ion.
METALLIC TRIOXOCARBONATE (IV) SALTS C032-
PREPARATION OF INSOLUBLE CO2-3
All trioxocarbonate(iv) salts are insoluble in water except soluble. Hence, they are prepared by double decomposition method, using aqueous NaCO3 e.g
Na2CO3(aq) + CuSO4(aq) CUCO3(s) + Na2SO4(aq)
Na2CO3(aq)+ Zncl2(aq) ZnCO3(s) + 2NaCl(aq
White
METHOD 2: Ca[OH]2(aq) + CO2(g) CaCO3(s) + H2O(l)
PROPERTIES OF SALTS
All trioxocarbonate(iv) salts are insoluble in water, except those of Na, K and NH4 which are soluble.
They dissolve in water to produce alkaline solutions. This is because they are salts of strong bases and weak acid, hence, they hydrolysed in water to produce alkaline
Solutions’
e.g K2CO3(s) + 2H2O 2KOH(aq) + H2CO3(aq)
3. All trioxocarbonate(IV) salts except those of potassium and Sodium, decompose on heating, to liberate CO2(g)
e.g. ZnCO3(s) ZnO(s) + Co2(g)
(NH4)2CO3(s) 2NH3(g) + H2O(g) + Co2(g)
Note: Na2CO3 and K2CO3 are not affected by heating, to liberate carbon (iv) oxide e.g
ZnCO3(s) + 2HCl(aq) ZnCl2(aq) + H2O(l) + CO2(g)
Ionically: CO3(s)2-+ 2H+(aq H2O(l) + CO2(g)
CHEMICAL TESTS FOR CO32- SALTS
Test on liquid on Solid (dry test)---------(a)
Small solid sample of salt is put in a test tube and few drops of dilute hydrochloric acid was added---- effervescence occur, then an odourless colourless gas was given off which in turn moist blue litmus paper slightly red and turns lime water. Gas is CO2(g)
Test (wet test) --------(b)
Barium chloride solution was added to few drops of solution of salt in test tube. A white precipitate was formed
CO2-3(ag) + BaCl2(aq) BaCO3(s) + 2Cl-(aq)
The precipitate is soluble in dilute HCl, to give a colourless solution.
BaCO3(s)+ 2HCl(aq) BaCl2(aq)+ H2CO3(aq)
TRIOXOCARBONATE (IV) ACID
Trioxocarbonate(IV) [carbonic acid], H2 CO3 is a very weak diabasic acid. It is obtained when carbon (iv) oxide dissolves in water. It is unsuitable; hence never isolated.
CO2(g) + H2O H2CO3(aq) 2H+(aq) + CO2-3(aq)
The acid forms both the normal and acid salts; i.e the acid ionizes into two stages;
H2CO3(aq) H2CO3(aq) H+(aq) + HCO-3(aq)
HCO-3(aq) H+(aq) + CO2-3(aq)
Uses of trioxocarbonate (IV) salts
Na2CO3 is used in softening hard water, in making soap and glass, and as an alkali in acid-base titration.
CaCO3 is used in making quick lime, cement and glass; in agriculture [in liming the soil – to reduce acidity]
EVALUATION
Describe the laboratory preparation of metallic trioxocarbonate(iv) salts
List two properties of trioxocarbonate(iv) salts
Give one method for preparation of trioxocarbonate(iv) acid
GENERAL EVALUATION
OBJECTIVE TEST
Where else is CO2 found in Free State apart from the atmosphere. A. carbonated trees B. dissolved form in water C. in corals D. in limestone region
All are decomposed by heat except A. BaCO3 B. CuCO3 C.AgCO3 D. ZnCO3
Which of the following trioxocarbonates (iv) are not decomposed by heat A. Calcium and Sodium trioxocarbonate (iv) C. Potassium and Zinc trioxocarbonate (iv) D. Zinc and Potassium trioxocarbonate (iv) E. Sodium and potassium trioxocarbonate (iv)
It is dangerous to stay in a badly ventilated room which has a charcoal fire because of the presence of A.CO2 B. CO C. Hydrogen D. Sulpur E. Methane
One of these gases is heavier than air and do not support combustion. A. CO B. CO2 C. H2O D. N2O
ESSAY QUESTIONS
Name one process which. (i) removes carbon (ii) fixes atmospheric nitrogen as trionitrate (iii) oxide from the atmosphere (iv) in the soil
Describe one of the method of Laboratary preparation of Carbon(II)oxide
Describe one of the method of laboratory preparation of (CO2(g)) Carbon (iv) oxide
Explain fully how CO2(g) can be detected in the laboratory.
How can you differentiate trioxocarbonate (iv) salt and trioxocarbonate (iv) acid with at least two points.
WEEKEND ASSIGNMENT:
Read comprehensive certificate chemistry 2nd edition by G.N.C Ohia, G.I. Amasiatu, J.O. Ajagbe, G.O Ojokuku and U. Mohammed pages 95-102
PRE READING ASSIGNMENT
Read hydrocarbon ant its main classes, crude oil and natural gas and importance of hydrocarbons.
WEEKEND ACTIVITY:
Explain in detail, the laboratory preparation of (i) CO (g) (ii) CO2(g) (iii) CO2-3 salts (iv)HCO3respectively.
REFERENCE TEXTS:
G.N.C Ohia, G.I. Amasiatu, J.O. Ababa, G.O Ojokuku and U. Mohammed.
Revised Edition Understanding Chemistry for schools and colleges by Godwin O. Ojokuku
WEEK 8
TOPIC: CARBON AND ITS COMPOUNDS
SUB TOPICS: I. Hydrocarbon and its main classes
II.Crude Oil and Natural gas
III.Importance of hydrocarbon
HYDRO CARBON AND ITS MAIN CLASSES
Hydrocarbons are organic compounds containing carbon and hydrogen only or organic hydrocarbon compounds are classified into
Aliphatic compounds
Aromatic compounds
Aliphatic compounds are classified into two sub-classes:
A cyclic compounds
Cyclic compounds
In acyclic compounds the molecules are made up of straight chin carbon atoms or branch chain e.g.
Butane (a straight chain compound)
2 methyl butane (a branched chain compound)
In cyclic compounds the end carbon atoms of an open aliphatic chain can also join together to form a closed system or ring e.g.
Cyclopropane
AROMATIC COMPOUNDS
Aromatic compounds are Benzene or derivative of benzene (that is compounds whose structures are based on the structure of benzene)
Due to resonance exhibit by the structures of benzene, i.e.
(ii)
The structure of benzene would be (i) or (ii)
Conventionally the structure of benzene is now a hexagon with a ring within it.
Examples of other derivatives of benzene,
OH (b) CH3 (c) CH3
Phenol Toluene Xylene
EVALUATION:
Name the following aliphatic compounds.
(a) H H H H H (b) H H H H H
H C C C C C H H C C C C C H
H H H H H H H H H
H C H
H
H
H C H
(c) H H
H
H C C C C H
H H H
H C H
H
CRUDE OIL AND NATURAL GAS
Another name for crude oil is petroleum. It is the chief source of hydrocarbons. Crude oil occurs as a dark, sticky, viscous liquid. It is believed that crude oil is formed by the gradual decomposition of the remains of marine plants and animals that became incorporated in the sediment and rocks formed at the bottom of the sea.
Crude oil is a mixture of gaseous, liquid and solid alkanes, cycloalkanes, aromatic hydrocarbons etc.
Natural gas; Natural gas is usually found together with crude oil; and water in traps or reservoirs in between some layers of rocks at the bottom of the sea. Natural gas consists mainly of methane. It is used as a domestic and industrial fuel.
In Nigeria crude oil is found in Oloibiri in 1956. In Niger Delta, Calabar and in Burntu in Delta state.
Various Fractions of crude oil are:
Petroleum gases
Petroleum ethers and ligron
Petrol
Kerosene
Gas oil and diesel oil
Lubricating oil
Bitumen and other residues
Petroleum gases- used mainly as fuels for homes and industries.
Petroleum ethers are used as organic solvents. Petrol is used as fuels for aero planes and motor vehicles. A solvent for paints and grease for heating and diesel oil are used mainly as fuels materials for the cracking process.
Lubricating oils used for lubricating moving parts of engines and machines.
Bitumen and other residues used forsurfacing roads and air fields and other residues may be used as fuel in protective paints and pipecoating and waterproofing roofs.
FRACTIONAL DISTILATION OF CRUDE OIL
EVALUATION:
1. Name some places in the Niger Delta in Nigeria where crude oil is found.
Write short not on this: IMPORTANCE OF HYDROCARBONS.
GENERAL EVALUATION
OBJECTIVE TEST:
Oil deposits in Nigeria are (a) on land and offshore (b) only offshore (c) mainly imported (d) downstream
Fractional distillation involves the following process (a) boiling (b) boiling and condensation (c) boiling, evaporation and condensation (d) condensation and collection
Which is the odd- one out of? (a) petroleum ether, petroleum gases, kerosene (b) gas oil and diesel lubricating oil (c) petroleum ether and bitumen (d) Haemitite and asphalt
Which of the following is a source of hydrocarbons? (a) Haemitite (b) marble (c) coal (d) slag
Crude oil can be obtained in Nigeria in the following places except. (a) Afam (b) Abata (c) Owaza (d) Kano
ESSAY QUESTIONS
Describe how you would show that crude oil is not a single compound.
(a) What are hydrocarbons? (b) Give three examples and their main sources in nature.
With the help of a diagram, briefly describe the industrial fractionation of petroleum.
Write short notes on (a) crude oil (b) Natural gas
Name four fractions of petroleum stating their uses.
WEEKEND ASSIGNMENT:
Read the topic ‘Fractional distillation of crude oil’
WEEKEND ACTIVITY:
On a cardboard sheet draw how crude oil and natural gases are formed.
PRE READING ASSIGNMENT:
Read all the notes for this third term.
SUB TOPICS: I. Hydrocarbon and its main classes
II.Crude Oil and Natural gas
III.Importance of hydrocarbon
HYDRO CARBON AND ITS MAIN CLASSES
Hydrocarbons are organic compounds containing carbon and hydrogen only or organic hydrocarbon compounds are classified into
Aliphatic compounds
Aromatic compounds
Aliphatic compounds are classified into two sub-classes:
A cyclic compounds
Cyclic compounds
In acyclic compounds the molecules are made up of straight chin carbon atoms or branch chain e.g.
Butane (a straight chain compound)
2 methyl butane (a branched chain compound)
In cyclic compounds the end carbon atoms of an open aliphatic chain can also join together to form a closed system or ring e.g.
Cyclopropane
AROMATIC COMPOUNDS
Aromatic compounds are Benzene or derivative of benzene (that is compounds whose structures are based on the structure of benzene)
Due to resonance exhibit by the structures of benzene, i.e.
(ii)
The structure of benzene would be (i) or (ii)
Conventionally the structure of benzene is now a hexagon with a ring within it.
Examples of other derivatives of benzene,
OH (b) CH3 (c) CH3
Phenol Toluene Xylene
EVALUATION:
Name the following aliphatic compounds.
(a) H H H H H (b) H H H H H
H C C C C C H H C C C C C H
H H H H H H H H H
H C H
H
H
H C H
(c) H H
H
H C C C C H
H H H
H C H
H
CRUDE OIL AND NATURAL GAS
Another name for crude oil is petroleum. It is the chief source of hydrocarbons. Crude oil occurs as a dark, sticky, viscous liquid. It is believed that crude oil is formed by the gradual decomposition of the remains of marine plants and animals that became incorporated in the sediment and rocks formed at the bottom of the sea.
Crude oil is a mixture of gaseous, liquid and solid alkanes, cycloalkanes, aromatic hydrocarbons etc.
Natural gas; Natural gas is usually found together with crude oil; and water in traps or reservoirs in between some layers of rocks at the bottom of the sea. Natural gas consists mainly of methane. It is used as a domestic and industrial fuel.
In Nigeria crude oil is found in Oloibiri in 1956. In Niger Delta, Calabar and in Burntu in Delta state.
Various Fractions of crude oil are:
Petroleum gases
Petroleum ethers and ligron
Petrol
Kerosene
Gas oil and diesel oil
Lubricating oil
Bitumen and other residues
Petroleum gases- used mainly as fuels for homes and industries.
Petroleum ethers are used as organic solvents. Petrol is used as fuels for aero planes and motor vehicles. A solvent for paints and grease for heating and diesel oil are used mainly as fuels materials for the cracking process.
Lubricating oils used for lubricating moving parts of engines and machines.
Bitumen and other residues used forsurfacing roads and air fields and other residues may be used as fuel in protective paints and pipecoating and waterproofing roofs.
FRACTIONAL DISTILATION OF CRUDE OIL
EVALUATION:
1. Name some places in the Niger Delta in Nigeria where crude oil is found.
Write short not on this: IMPORTANCE OF HYDROCARBONS.
GENERAL EVALUATION
OBJECTIVE TEST:
Oil deposits in Nigeria are (a) on land and offshore (b) only offshore (c) mainly imported (d) downstream
Fractional distillation involves the following process (a) boiling (b) boiling and condensation (c) boiling, evaporation and condensation (d) condensation and collection
Which is the odd- one out of? (a) petroleum ether, petroleum gases, kerosene (b) gas oil and diesel lubricating oil (c) petroleum ether and bitumen (d) Haemitite and asphalt
Which of the following is a source of hydrocarbons? (a) Haemitite (b) marble (c) coal (d) slag
Crude oil can be obtained in Nigeria in the following places except. (a) Afam (b) Abata (c) Owaza (d) Kano
ESSAY QUESTIONS
Describe how you would show that crude oil is not a single compound.
(a) What are hydrocarbons? (b) Give three examples and their main sources in nature.
With the help of a diagram, briefly describe the industrial fractionation of petroleum.
Write short notes on (a) crude oil (b) Natural gas
Name four fractions of petroleum stating their uses.
WEEKEND ASSIGNMENT:
Read the topic ‘Fractional distillation of crude oil’
WEEKEND ACTIVITY:
On a cardboard sheet draw how crude oil and natural gases are formed.
PRE READING ASSIGNMENT:
Read all the notes for this third term.
