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Question 1 Report
(a) What is an electrochemical cell?
(b) State three differences between an electrochemical cell and an electrolytic cell.
(c) Explain briefly what would be observed when powdered zinc is added to a solution of copper (II) tetraoxosulphate (IV) in a beaker.
d(i) Write an equation for the reaction in 1(c);
(ii) State the type of reaction which took place in 1(c);
(e) Name two gases which should be prepared in a fume chamber.
(f) Give three factors that favour cracking.
(g) Give the reason why noble gases are chemically inert.
(h) State four properties of a homologous series.
(i) What is global warming?
(j)State one cause of global warming.
(a) An electrochemical cell is a device that can generate electrical energy from the chemical reactions occurring in it, or use the electrical energy supplied to it to facilitate chemical reactions in it.
(b)
| Electrochemical cell | Electrolytic cell |
| Chemical reaction produces electric current | Electricity is used to produce chemical reaction |
| The positive electrode is cathode | Cathode is the negative electrode |
| Anode is the negative electrode | Anode is the positive electrode |
| It does not require any external source of energy. | It does require an external source of energy, thus it is non-spontaneous |
| Electrodes are in separate compartments | Electrodes are in the same compartment |
(c) When powdered zinc is added to a copper (II) tetraoxosulphate (IV) solution, a reddish-brown solid of copper metal will form on the zinc, and the blue solution will become colourless as zinc displaces copper.
d(i) The reaction can be represented by the following equation: Zn(s) + CuSO\(_4\)(aq) → ZnSO\(_4\)(aq) + Cu(s).
(ii) Oxidation-Reduction (Redox) reaction
(e) Ammonia, Chlorine, Hydrogen Sulphide
(f) Factors that favor cracking include: high temperatures, high pressures, the presence of catalysts, and the nature of the material's composition and structure.
(g) Noble gases are chemically inert because their outermost electron shells are completely filled, making them stable and unlikely to react with other elements.
(h) Properties of homologous series include the following:
- All members of a homologous series have the same general formula.
- All members of a homologous series have the same functional group. e.g Alcohols contain the (-OH) functional group.
- The molecular formula of successive members of a homologous series differs by CH\(_2\).
- Members of a homologous series have similar physical properties, such as melting point, boiling point, and density.
- Members of a homologous series have similar chemical properties because they have the same functional group.
(i) Global warming is the increase in Earth's average temperature caused by greenhouse gases. Greenhouse gases trap heat in the atmosphere, which warms the planet. Carbon dioxide, methane, and nitrous oxide are greenhouse gases that trap heat in the atmosphere.
(j) Global warming is primarily caused by
- burning of fossil fuels
- increased concentration of greenhouse gases, like carbon dioxide (CO\(_2\))
Answer Details
(a) An electrochemical cell is a device that can generate electrical energy from the chemical reactions occurring in it, or use the electrical energy supplied to it to facilitate chemical reactions in it.
(b)
| Electrochemical cell | Electrolytic cell |
| Chemical reaction produces electric current | Electricity is used to produce chemical reaction |
| The positive electrode is cathode | Cathode is the negative electrode |
| Anode is the negative electrode | Anode is the positive electrode |
| It does not require any external source of energy. | It does require an external source of energy, thus it is non-spontaneous |
| Electrodes are in separate compartments | Electrodes are in the same compartment |
(c) When powdered zinc is added to a copper (II) tetraoxosulphate (IV) solution, a reddish-brown solid of copper metal will form on the zinc, and the blue solution will become colourless as zinc displaces copper.
d(i) The reaction can be represented by the following equation: Zn(s) + CuSO\(_4\)(aq) → ZnSO\(_4\)(aq) + Cu(s).
(ii) Oxidation-Reduction (Redox) reaction
(e) Ammonia, Chlorine, Hydrogen Sulphide
(f) Factors that favor cracking include: high temperatures, high pressures, the presence of catalysts, and the nature of the material's composition and structure.
(g) Noble gases are chemically inert because their outermost electron shells are completely filled, making them stable and unlikely to react with other elements.
(h) Properties of homologous series include the following:
- All members of a homologous series have the same general formula.
- All members of a homologous series have the same functional group. e.g Alcohols contain the (-OH) functional group.
- The molecular formula of successive members of a homologous series differs by CH\(_2\).
- Members of a homologous series have similar physical properties, such as melting point, boiling point, and density.
- Members of a homologous series have similar chemical properties because they have the same functional group.
(i) Global warming is the increase in Earth's average temperature caused by greenhouse gases. Greenhouse gases trap heat in the atmosphere, which warms the planet. Carbon dioxide, methane, and nitrous oxide are greenhouse gases that trap heat in the atmosphere.
(j) Global warming is primarily caused by
- burning of fossil fuels
- increased concentration of greenhouse gases, like carbon dioxide (CO\(_2\))
Question 2 Report
a(i) Write balanced chemical equations for the production of lead(II) chloride by:
I. direct combination of constituent elements;
II. double decomposition;
III. displacement reaction.
(ii) State one condition that would increase the rate of reaction for each of the reactions stated in 3a(i).
I. ........................... II. ......................... III. .......................
(b) Consider the following Chemical reaction in equilibrium:
2SO\(_2\)(g) + O\(_2\)(g) ⇌ 2SO\(_3\)\(_(g)\) ; ΔH = positive
(i) State two conditions that would increase the yield of SO\(_3\)\(_(g)\)
(ii) If 60cm\(^3\) of SO\(_2\) reacts with 40cm\(^3\) of O\(_2\), determine the volume of the residual gas, assuming that the reaction goes to completion in a cylinder.
(iii) What is the change in the oxidation number of sulphur in the reaction in 3(b) ?
(c) Using structural diagrams, explain why cyclopropane is not an isomer of n-propane.
(d) A structural organic compound X containing three carbon atoms reacted with butanoic acid in the presence of dilute H\(_2\)SO\(_4\) to form a sweet smelling compound Y.
(i) Name compounds X and Y.
(ii) State the functional group present in X.
(iii) Write an equation for the reaction between X and butanoic acid.
a(i) Production of Lead(II)Chloride by:
I. direct combination : Pb + Cl\(_2\) → PbCl\(_2\)
II. double decomposition: Pb(NO₃)₂(aq) + 2NaCl(aq) → PbCl₂(s) + 2NaNO₃(aq)
III. displacement reaction: Pb + CuCl₂ → PbCl₂ + Cu.
(ii) Condition that would increase the rate of reaction for:
I. direct decomposition: increase the temperature, concentration of reactants, or introduce a catalyst.
II.double decomposition: increase the concentration of reactants, and/or increase the surface area of solid reactants.
III. displacement reaction: increase the temperature.
b(i) Conditions that would increase the yield of SO\(_3\)\(_(g)\)
- Increase in temperature,
- Increase in pressure,
- Removing the product formed
(ii) 2SO\(_2\)(g) + O\(_2\)(g) ⇌ 2SO\(_3\)\(_(g)\)
Reacting ratio: 2 moles : 1 mole
Total Reacting Volume: 60cm\(^3\) : 40cm\(^3\)
Actual reacted Volume: 60cm\(^3\) : 30cm\(^3\) → (Following the ratio from the balanced chemical equation)
Residual Volume: (Total reacting volume - Actual reacted volume)
For SO\(_2\): 60 - 60 = 0 ⇒ SO\(_2\) was completely used up in the reaction, hence it is called the limiting reactant.
For O\(_2\) : 40 - 30 = 10cm\(^3\) → Volume of the residual gas is 10cm\(^3\).
(iii) Change in the oxidation number of sulphur in the reaction: 2SO\(_2\)(g) + O\(_2\)(g) ⇌ 2SO\(_3\)\(_(g)\)
i.e From SO\(_2\)(g) → SO\(_3\)\(_(g)\)
S + O\(_2\)= 0 → S + O\(_3\) = 0
S + (-2)2 = 0 → S + (-2)3 = 0
S - 4 =0 → S - 6 = 0
S = + 4 → S = + 6
Change in oxidation state is from +4 to +6.
(c) cyclopropane n-propane
CH\(_2\) H H H
/ \ I I I
CH\(_2\) — CH\(_2\) H —C — C — C — H
( C\(_3\)H\(_6\)) I I I
H H H ( C\(_3\)H\(_8\))
For any two or more compounds to be isomers, their molecular formula must be the same while their structural formular would be different from each other. In this case, the molecular formula of the two compounds are not the same. i.e C\(_3\)H\(_6\) and C\(_3\)H\(_8\) are not the same, hence cyclopropane cannot be said to be an isomer of n-propane.
d(i) Compound X is Propanol while Compound Y is Propylbutanoate
(ii) The functional group present in X is - OH (hydroxyl)
(iii) Propanol + Butanoic acid → Propyl butanoate + Water
CH\(_3\)CH\(_2\)CH\(_2\)OH + CH\(_3\)CH\(_2\)CH\(_2\)COOH → CH\(_3\)CH\(_2\)CH\(_2\)COOCH\(_2\)CH\(_2\)CH\(_3\) + H\(_2\)O
Answer Details
a(i) Production of Lead(II)Chloride by:
I. direct combination : Pb + Cl\(_2\) → PbCl\(_2\)
II. double decomposition: Pb(NO₃)₂(aq) + 2NaCl(aq) → PbCl₂(s) + 2NaNO₃(aq)
III. displacement reaction: Pb + CuCl₂ → PbCl₂ + Cu.
(ii) Condition that would increase the rate of reaction for:
I. direct decomposition: increase the temperature, concentration of reactants, or introduce a catalyst.
II.double decomposition: increase the concentration of reactants, and/or increase the surface area of solid reactants.
III. displacement reaction: increase the temperature.
b(i) Conditions that would increase the yield of SO\(_3\)\(_(g)\)
- Increase in temperature,
- Increase in pressure,
- Removing the product formed
(ii) 2SO\(_2\)(g) + O\(_2\)(g) ⇌ 2SO\(_3\)\(_(g)\)
Reacting ratio: 2 moles : 1 mole
Total Reacting Volume: 60cm\(^3\) : 40cm\(^3\)
Actual reacted Volume: 60cm\(^3\) : 30cm\(^3\) → (Following the ratio from the balanced chemical equation)
Residual Volume: (Total reacting volume - Actual reacted volume)
For SO\(_2\): 60 - 60 = 0 ⇒ SO\(_2\) was completely used up in the reaction, hence it is called the limiting reactant.
For O\(_2\) : 40 - 30 = 10cm\(^3\) → Volume of the residual gas is 10cm\(^3\).
(iii) Change in the oxidation number of sulphur in the reaction: 2SO\(_2\)(g) + O\(_2\)(g) ⇌ 2SO\(_3\)\(_(g)\)
i.e From SO\(_2\)(g) → SO\(_3\)\(_(g)\)
S + O\(_2\)= 0 → S + O\(_3\) = 0
S + (-2)2 = 0 → S + (-2)3 = 0
S - 4 =0 → S - 6 = 0
S = + 4 → S = + 6
Change in oxidation state is from +4 to +6.
(c) cyclopropane n-propane
CH\(_2\) H H H
/ \ I I I
CH\(_2\) — CH\(_2\) H —C — C — C — H
( C\(_3\)H\(_6\)) I I I
H H H ( C\(_3\)H\(_8\))
For any two or more compounds to be isomers, their molecular formula must be the same while their structural formular would be different from each other. In this case, the molecular formula of the two compounds are not the same. i.e C\(_3\)H\(_6\) and C\(_3\)H\(_8\) are not the same, hence cyclopropane cannot be said to be an isomer of n-propane.
d(i) Compound X is Propanol while Compound Y is Propylbutanoate
(ii) The functional group present in X is - OH (hydroxyl)
(iii) Propanol + Butanoic acid → Propyl butanoate + Water
CH\(_3\)CH\(_2\)CH\(_2\)OH + CH\(_3\)CH\(_2\)CH\(_2\)COOH → CH\(_3\)CH\(_2\)CH\(_2\)COOCH\(_2\)CH\(_2\)CH\(_3\) + H\(_2\)O
Question 3 Report
SECTION B
a(i)Define each of the following terms;
I. Deliquescence II. efflorescence
(ii) Give one example of a substance that undergoes each of the processes in 2a(i)
b(i)What is meant by ionization energy?
(ii)The second ionization energy value of sodium is greater than the first ionization energy. Briefly give an explanation for this observation.
c(i) State Charles' law
(ii) Sketch a graph to illustrate Charles' law.
(iii) A gas occupies 150 cm\(^3\) at 21\(^0\)C. What would be its volume if the temperature is raised to 45\(^0\)C and the pressure is kept constant?
d(i)Write chemical equations to illustrate what happens when each of the following oxides is dissolved in water:
I. Sodium oxide;
II. Phosphorus(III) oxide;
III. Chlorine (VII) oxide
IV. Magnesium oxide
(ii) Arrange the solutions in 2d(i) in order of increasing acidity.
a(i)I. Deliquescence is the phenomenon where a solid substance absorbs moisture from the air and dissolves, turning into a liquid solution.
II. Efflorescence refers to the phenomenon or product of a substance losing water of crystallization, often resulting in a powdery or crusty deposit on a surface.
(ii)Examples of Deliquescence include; Calcium chloride (CaCl\(_2\)); Potassium hydroxide (KOH);Sodium hydroxide (NaOH); Magnesium chloride (MgCl\(_2\)); Zinc chloride (ZnCl\(_2\))
Example of Efflorescence include; washing soda, Glauber's salt, and copper sulphate, gypsum
b(i) Ionization energy is the minimum energy needed to remove an electron from a gaseous atom or ion, essentially measuring how strongly an atom holds onto its electrons.
(ii) The second ionization energy of sodium (Na) is higher than its first ionization energy because the second electron is removed from a positively charged ion (Na+), which experiences a stronger electrostatic attraction to the nucleus than the neutral atom.
c(i) Charles' law states that the volume of a given mass of gas is directly proportional to the temperature provided pressure remains constant.
(ii) A graph illustrating Charles' law: Volume on the y-axis and temperature on the -axis with a line intercepting the y-axis and drawn to the negative x-axis at - 273\(^0\)C.
(iii) Given:
V\(_1\) = 150 cm\(^3\) T\(_1\) = 21 + 273 = 294K
V\(_2\) = ? T\(_2\) = 45 + 273 = 318K
Using \(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)
V\(_2\) = \(\frac{V_1}{T_1}\times{T_2}\)
V\(_2\) = \(\frac{150}{294}\times{318}\)
V\(_2\) = 162.24 cm\(^3\)
d(i) I. Na₂O + H₂O → 2NaOH.
II. P\(_4\)O\(_6\) + 6H\(_2\)O → 4H\(_3\)PO\(_3\)
III. Cl₂O₇ + H₂O → 2HClO₄.
IV. MgO + H₂O → Mg(OH)₂.
d(ii) Increasing acidity is arranged from NaOH < Mg(OH)₂. < H\(_3\)PO\(_3\) < HClO₄.
Answer Details
a(i)I. Deliquescence is the phenomenon where a solid substance absorbs moisture from the air and dissolves, turning into a liquid solution.
II. Efflorescence refers to the phenomenon or product of a substance losing water of crystallization, often resulting in a powdery or crusty deposit on a surface.
(ii)Examples of Deliquescence include; Calcium chloride (CaCl\(_2\)); Potassium hydroxide (KOH);Sodium hydroxide (NaOH); Magnesium chloride (MgCl\(_2\)); Zinc chloride (ZnCl\(_2\))
Example of Efflorescence include; washing soda, Glauber's salt, and copper sulphate, gypsum
b(i) Ionization energy is the minimum energy needed to remove an electron from a gaseous atom or ion, essentially measuring how strongly an atom holds onto its electrons.
(ii) The second ionization energy of sodium (Na) is higher than its first ionization energy because the second electron is removed from a positively charged ion (Na+), which experiences a stronger electrostatic attraction to the nucleus than the neutral atom.
c(i) Charles' law states that the volume of a given mass of gas is directly proportional to the temperature provided pressure remains constant.
(ii) A graph illustrating Charles' law: Volume on the y-axis and temperature on the -axis with a line intercepting the y-axis and drawn to the negative x-axis at - 273\(^0\)C.
(iii) Given:
V\(_1\) = 150 cm\(^3\) T\(_1\) = 21 + 273 = 294K
V\(_2\) = ? T\(_2\) = 45 + 273 = 318K
Using \(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)
V\(_2\) = \(\frac{V_1}{T_1}\times{T_2}\)
V\(_2\) = \(\frac{150}{294}\times{318}\)
V\(_2\) = 162.24 cm\(^3\)
d(i) I. Na₂O + H₂O → 2NaOH.
II. P\(_4\)O\(_6\) + 6H\(_2\)O → 4H\(_3\)PO\(_3\)
III. Cl₂O₇ + H₂O → 2HClO₄.
IV. MgO + H₂O → Mg(OH)₂.
d(ii) Increasing acidity is arranged from NaOH < Mg(OH)₂. < H\(_3\)PO\(_3\) < HClO₄.
Question 4 Report
(a) Write a balanced chemical equation for each of the following reactions:
(i) ammonia gas with copper(II) oxide;
(ii) ammonia gas with oxygen gas;
(iii) aqueous potassium iodide with chlorine gas;
(iv) iron with dilute tetraoxosulphate (VI) acid;
(v) aqueous lead(II) trioxonitrate (V) with hydrogen chloride gas.
b(i) Describe briefly the process involved in the extraction of tin from tin ore.
(ii) Mention three uses of hydrogen.
(iii) State two physical properties of hydrogen.
(c) State the class of oxide to which each of the following compounds belong:
(i) Na\(_2\)O; (ii) ZnO; (iii)SO\(_2\); (iv) CO\(_2\); (v) N\(_2\)O.
a(i) 2NH\(_3\) + 3CuO → Cu + N\(_2\) + 3H\(_2\)O
(ii) 4NH\(_3\)(g) + 5O\(_2\)(g) → 4NO(g) + 6H\(_2\)O(g)
(iii) Cl₂(g) + 2 KI(aq) → 2 KCl(aq) + I₂(s)
(iv) Fe + H\(_2\)SO\(_4\) → FeSO\(_4\) + H\(_2\)
(v) Pb(NO\(_3\))\(_2\) + 2HCl → PbCl\(_2\) +2HNO\(_3\)
b(i) The process involved in the extraction of tin from tin ore
Tin extraction from its ore, primarily cassiterite (SnO₂), involves crushing, concentration (using techniques like gravity separation or flotation), smelting (heating with carbon to produce metallic tin), and finally, refining to achieve high purity.
The tin ore is first crushed and ground to a fine powder.This step aims to increase the tin content in the ore. Techniques like gravity separation, flotation, or magnetic separation are used to separate the tin-rich minerals from the gangue (waste rock). The concentrated ore is then heated with carbon in a furnace to a high temperature (around 1300-1400°C or 2375-2550°F) to reduce the tin oxide to metallic tin. The resulting impure tin is refined to achieve the desired purity for industrial applications.
(ii) Uses of hydrogen include the following:
- Hydrogen can be used in fuel cells to power vehicles.
- Hydrogen can be used to generate electricity.
- It is also used to produce "green steel".
- Hydrogen is used to extract tungsten from ore and copper from copper oxide.
- Hydrogen is used to synthesize ammonia.
- Hydrogen is used to produce nitric acid and nitrogenous fertilizers.
- Hydrogen is used to produce hydrogen chloride.
- It is used to produce water gas.
- Filling balloons.
(iii) Physical properties of hydrogen include;
- colourless,
- odourless,
- tasteless,
- highly flammable,
- It has a low density and
- low boiling and melting points.
c(i) Na\(_2\)O - basic oxide
(ii) ZnO - amphoteric oxide
(iii)SO\(_2\) - acidic oxide
(iv) CO\(_2\) - acidic oxide
(v) N\(_2\)O - neutral oxide
Answer Details
a(i) 2NH\(_3\) + 3CuO → Cu + N\(_2\) + 3H\(_2\)O
(ii) 4NH\(_3\)(g) + 5O\(_2\)(g) → 4NO(g) + 6H\(_2\)O(g)
(iii) Cl₂(g) + 2 KI(aq) → 2 KCl(aq) + I₂(s)
(iv) Fe + H\(_2\)SO\(_4\) → FeSO\(_4\) + H\(_2\)
(v) Pb(NO\(_3\))\(_2\) + 2HCl → PbCl\(_2\) +2HNO\(_3\)
b(i) The process involved in the extraction of tin from tin ore
Tin extraction from its ore, primarily cassiterite (SnO₂), involves crushing, concentration (using techniques like gravity separation or flotation), smelting (heating with carbon to produce metallic tin), and finally, refining to achieve high purity.
The tin ore is first crushed and ground to a fine powder.This step aims to increase the tin content in the ore. Techniques like gravity separation, flotation, or magnetic separation are used to separate the tin-rich minerals from the gangue (waste rock). The concentrated ore is then heated with carbon in a furnace to a high temperature (around 1300-1400°C or 2375-2550°F) to reduce the tin oxide to metallic tin. The resulting impure tin is refined to achieve the desired purity for industrial applications.
(ii) Uses of hydrogen include the following:
- Hydrogen can be used in fuel cells to power vehicles.
- Hydrogen can be used to generate electricity.
- It is also used to produce "green steel".
- Hydrogen is used to extract tungsten from ore and copper from copper oxide.
- Hydrogen is used to synthesize ammonia.
- Hydrogen is used to produce nitric acid and nitrogenous fertilizers.
- Hydrogen is used to produce hydrogen chloride.
- It is used to produce water gas.
- Filling balloons.
(iii) Physical properties of hydrogen include;
- colourless,
- odourless,
- tasteless,
- highly flammable,
- It has a low density and
- low boiling and melting points.
c(i) Na\(_2\)O - basic oxide
(ii) ZnO - amphoteric oxide
(iii)SO\(_2\) - acidic oxide
(iv) CO\(_2\) - acidic oxide
(v) N\(_2\)O - neutral oxide
Question 5 Report
a(i) Write the chemical formula of alumina.
(ii) In the extraction of aluminium, state one compound that is used;
I. to obtain alumina from Bauxite
II. as solvent for alumina.
(iii) Name the electrodes used in the extraction of aluminium.
(iv) Give one reason why the extraction of aluminium is expensive.
(v) In the extraction of aluminium:
I. name the substance liberated at the anode;
II. write the equation for the reaction that leads to decrease in the size of the anode.
b(i) Give two ions that cause hardness of water.
(ii) State two advantages and two disadvantages of hard water.
c(i) What is meant by destructive distillation of coal?
(ii) Name four products obtained from the destructive distillation of coal.
d(i) Name two gases which can be used to demonstrate the fountain experiment.
(ii) Give the reason why the gases named in 5d(i) are used.
a(i) The chemical formula for alumina,(aluminium oxide) is Al\(_2\)O\(_3\)
(ii) In the extraction of aluminium,the compound that is used;
I. to obtain alumina from Bauxite - Sodium hydroxide, NaOH
II. as solvent for alumina - Cryolite, Na\(_3\)AlF\(_6\)
(iii) The electrodes used in the extraction of aluminium are
- cathode (negative electrode) graphite,
- anode (positive electrode) carbon rods or slabs.
(iv)The extraction of aluminium is expensive due to the high energy requirements of the electrolysis process, which involves purifying bauxite, melting aluminium oxide, and using electricity to break down electrolytes.
(v) In the extraction of aluminium:
I. the substance liberated at the anode is oxygen gas (O₂)
II. the equation for the reaction that leads to decrease in the size of the anode is: C + O\(_2\) → CO\(_2\)
b(i) Ions that cause hardness of water are Ca\(^{2+}\) and Mg\(^{2+}\)
(ii) Advantages of hard water
- strengthening bones and teeth,
- potentially aiding digestion, and
- reducing the risk of cardiovascular disease.
- improves the taste of water due to the presence of the ions.
Disadvantages of hard water
- skin and hair dryness,
- reduced soap effectiveness,
- potential appliance damage, and plumbing issues.
c(i) Destructive distillation of coal is a process of heating coal in the absence of air (or with limited oxygen) to break down its complex molecules into simpler, useful products like coke, coal gas, coal tar, and ammoniacal liquor.
(ii) products obtained from the destructive distillation of coal are:
- coke
- coal gas
- coal tar and
- ammoniacal liquor
d(i) Gases which can be used to demonstrate the fountain experiment are;
- Ammonia, NH\(_3\)
- Hydrogen chloride gas, HCl
(ii) Ammonia (NH\(_3\)) and hydrogen chloride (HCl) are used in the fountain experiment to demonstrate the high solubility of gases in water. When water is introduced into a flask containing either gas, the gas dissolves rapidly, creating a pressure drop that forces water upwards, forming a "fountain".
Answer Details
a(i) The chemical formula for alumina,(aluminium oxide) is Al\(_2\)O\(_3\)
(ii) In the extraction of aluminium,the compound that is used;
I. to obtain alumina from Bauxite - Sodium hydroxide, NaOH
II. as solvent for alumina - Cryolite, Na\(_3\)AlF\(_6\)
(iii) The electrodes used in the extraction of aluminium are
- cathode (negative electrode) graphite,
- anode (positive electrode) carbon rods or slabs.
(iv)The extraction of aluminium is expensive due to the high energy requirements of the electrolysis process, which involves purifying bauxite, melting aluminium oxide, and using electricity to break down electrolytes.
(v) In the extraction of aluminium:
I. the substance liberated at the anode is oxygen gas (O₂)
II. the equation for the reaction that leads to decrease in the size of the anode is: C + O\(_2\) → CO\(_2\)
b(i) Ions that cause hardness of water are Ca\(^{2+}\) and Mg\(^{2+}\)
(ii) Advantages of hard water
- strengthening bones and teeth,
- potentially aiding digestion, and
- reducing the risk of cardiovascular disease.
- improves the taste of water due to the presence of the ions.
Disadvantages of hard water
- skin and hair dryness,
- reduced soap effectiveness,
- potential appliance damage, and plumbing issues.
c(i) Destructive distillation of coal is a process of heating coal in the absence of air (or with limited oxygen) to break down its complex molecules into simpler, useful products like coke, coal gas, coal tar, and ammoniacal liquor.
(ii) products obtained from the destructive distillation of coal are:
- coke
- coal gas
- coal tar and
- ammoniacal liquor
d(i) Gases which can be used to demonstrate the fountain experiment are;
- Ammonia, NH\(_3\)
- Hydrogen chloride gas, HCl
(ii) Ammonia (NH\(_3\)) and hydrogen chloride (HCl) are used in the fountain experiment to demonstrate the high solubility of gases in water. When water is introduced into a flask containing either gas, the gas dissolves rapidly, creating a pressure drop that forces water upwards, forming a "fountain".
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