1. (a) Define the term solubility.
   
   [2 marks]
   

   Answer

   ×
   

   Solubility

   Solubility is defined as the maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature and pressure to form a homogeneous solution.

   It shows how much of a substance (called the solute) can dissolve in a liquid (called the solvent), such as water.

   Units: Solubility is usually expressed in grams of solute per 100 grams of solvent (g/100g) or in mol/L (molarity).

   Example: At 25°C, the solubility of table salt (NaCl) in water is about 36g per 100g of water. If more than 36g is added, the extra salt will not dissolve and will remain at the bottom.

   
   
   

   (b) State two factors that affect solubility.
   
   [2 marks]
   

   Answer

   ×
   

   State two factors That Affect Solubility

   The solubility of a substance depends on several factors. These factors influence how easily a solute dissolves in a solvent.

   1. Temperature:
   
   Generally, increasing the temperature increases the solubility of solids and liquids in a solvent. However, for gases, solubility decreases as temperature increases.
   
   Example: Sugar dissolves faster in hot water than in cold water.

   2. Pressure:
   
   Pressure has a significant effect only on the solubility of gases. The higher the pressure, the more gas can dissolve in a liquid.
   
   Example: Carbon dioxide is dissolved in soft drinks under high pressure. When the bottle is opened, the pressure drops and gas escapes.

   3. Nature of the Solute and Solvent:
   
   Solubility depends on the chemical nature of the solute and solvent. Polar solutes dissolve well in polar solvents, while non-polar solutes dissolve in non-polar solvents.
   
   Example: Salt (NaCl), a polar compound, dissolves in water, which is also polar. Oil (non-polar) does not dissolve in water.

   4. Particle Size:
   
   Smaller solute particles dissolve faster due to a larger surface area exposed to the solvent.
   
   Example: Powdered sugar dissolves faster than sugar cubes in the same amount of water.

   5. Stirring (Agitation):
   
   Stirring increases the contact between solute and solvent particles, helping the solute to dissolve more quickly.
   
   Example: Stirring salt in water speeds up the dissolving process.

   
   
   

   (c) An element Q has two isotopes, ³²₁₅Q and ³³₁₅Q, in the ratio 1 : 4.
   
   Calculate the relative atomic mass of Q.
   
   [3 marks]
   

   Answer

   ×
   

   Calculation of Relative Atomic Mass

   Two isotopes of element Q:

   ¹⁵₃₂Q → mass number = 32

   ¹⁵₃₃Q → mass number = 33

   Ratio of the isotopes = 1 : 4

   This means for every 1 atom of ¹⁵₃₂Q, there are 4 atoms of ¹⁵₃₃Q.

   To calculate the relative atomic mass, we use the weighted average formula:

   $$\begin{gathered} \begin{array}{l}\text{Relative Atomic Mass<br>}\\ =\frac{(32\times 1)+(33\times 4)}{1+4}\\ \\ \\ =\frac{32+132}{5}\\ \\ \\ =\frac{164}{5}\\ \\ \\ =32.8\end{array} \end{gathered}$$

   Answer: The relative atomic mass of Q is 32.8.

   
   
   

   (d) State the types of binding forces present in [Cu(H₂O)₄]Cl₂
   
   [3 marks]
   

   Answer

   ×
   

   Types of Binding Forces in [Cu(H₂O)₄]Cl₂

   The binding forces present in the complex [Cu(H₂O)₄]Cl₂ are:

   1. Coordinate (Dative Covalent) Bonding:
   
   This type of bond occurs between the copper ion (Cu²⁺) and the water molecules (H₂O) in the complex. In the coordination sphere of copper, each water molecule donates a lone pair of electrons from the oxygen atom to form a coordinate bond with the Cu²⁺ ion.

   2. Ionic Bonding:
   
   The chloride ions (Cl^-) are ionically bonded to the copper complex [Cu(H₂O)₄]²⁺.The positively charged copper complex attracts the negatively charged chloride ions through electrostatic forces, forming ionic bonds.

   Thus, the two types of bonding forces in [Cu(H₂O)₄]Cl₂ are:

   • Coordinate (dative covalent) bonding between Cu²⁺ and H₂O
   • Ionic bonding between the [Cu(H₂O)₄]²⁺ complex and the chloride ions (Cl^-).

   
   
   

   (e) State three postulates of the kinetic theory of matter.
   
   [3 marks]
   

   Answer

   ×
   

   Postulates of the Kinetic Theory of Matter

   The kinetic theory of matter explains the behavior of particles in solids, liquids, and gases. The main postulates of the kinetic theory are as follows:

   1. Matter is made up of tiny particles:
   
   All matter is composed of very small particles, such as atoms or molecules, that are in constant motion.

   2. Particles are in constant random motion:
   
   The particles move randomly in all directions. In gases, the particles move freely and rapidly, while in liquids, they move more slowly and are somewhat restricted. In solids, the particles vibrate in place.

   3. Particles interact with each other:
   
   There are forces of attraction and repulsion between the particles. In solids, the attractive forces are stronger than the repulsive forces, leading to a fixed structure. In liquids, the forces are weaker, and in gases, the forces are minimal.

   4. The energy of the particles is proportional to the temperature:
   
   The temperature of a substance is directly related to the average kinetic energy of its particles. As the temperature increases, the particles move faster, and as the temperature decreases, the particles move slower.

   5. Collisions between particles are elastic:
   
   When particles collide with each other or with the walls of a container, the collisions are elastic. This means there is no loss of kinetic energy during the collision.

   
   
   

   (f) Explain briefly why the molecule of a gas has no fixed volume.
   
   [2 marks]
   

   Answer

   ×
   

   Why The Molecule of a Gas Has No Fixed Volume?

   The molecules of a gas have no fixed volume due to the following reasons:

   1. Molecules are widely spaced:
   
   In a gas, the molecules are far apart compared to solids and liquids. This large distance between molecules means that gas molecules are not restricted to a specific volume.

   2. Random motion of molecules:
   
   Gas molecules move randomly in all directions and at high speeds. As they move, they spread out to fill the entire volume of the container, meaning the volume of the gas adjusts to the container’s size.

   3. Low intermolecular forces:
   
   The forces of attraction between gas molecules are very weak. This allows the molecules to move freely and spread out in any available space, leading to no fixed volume for the gas.

   4. Compressibility:
   
   Gases are highly compressible, meaning that their volume can be reduced by applying pressure. This is further evidence that gas molecules do not have a fixed volume.

   In summary, the lack of a fixed volume in a gas is due to the random movement of molecules, the large distance between them, weak intermolecular forces, and their ability to compress and expand in response to changes in pressure or temperature.

   
   
   

   (g) A gas occupies a volume of 200 cm³ at s.t.p. What volume would it occupy at 100 mm Hg and 27°C?
   
   [3 marks]
   

   Answer

   ×
   

   Calculation of New Volume of Gas

   Given:

   • Initial Volume, V₁ = 200 cm³
   • Standard Temperature, T₁ = 273 K
   • Standard Pressure, P₁ = 760 mm Hg
   • Final Temperature, T₂ = 300 K
   • Final Pressure, P₂ = 100 mm Hg

   Using the Combined Gas Law:

   $$\frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2}$$

   Solving for V₂:

   $$V_2=\frac{P_1{V}_1{T}_2}{P_2{T}_1}$$ $$V_2=\frac{760\times 200\times 300}{100\times 273}=\frac{45600000}{27300}=1670.33 \mathrm{cm}{3}^{}$$

   Answer: The gas would occupy 1670.33 cm³ at 100 mm Hg and 27°C.

   
   
   

   (h) What is a weak acid?
   
   [2 marks]
   

   Answer

   ×
   

   What is a Weak Acid?

   A weak acid is an acid that only partially ionizes in solution. This means that only a small fraction of the acid molecules dissociate to produce hydrogen ions (H⁺) in water.

   As a result, weak acids have a relatively low concentration of hydrogen ions in solution compared to strong acids.

   Examples: Acetic acid (CH₃COOH), carbonic acid (H₂CO₃), and citric acid.

   Note: Weak acids have higher pH values than strong acids at the same concentration.

   
   
   

   (i) State three chemical properties of acids.
   
   [3 marks]
   

   Answer

   ×
   

   Chemical Properties of Acids

   Acids display the following key chemical properties:

   1. Reaction with Metals:
   Acids react with reactive metals to produce salt and hydrogen gas.
   Example: Zn + 2HCl → ZnCl₂ + H₂

   2. Neutralization:
   Acids neutralize bases to form salt and water.
   Example: HCl + NaOH → NaCl + H₂O

   3. Reaction with Carbonates and Bicarbonates:
   Acids react with carbonates and bicarbonates to produce salt, carbon dioxide, and water.
   Example: 2HCl + Na₂CO₃ → 2NaCl + CO₂ + H₂O

   4. Electrical Conductivity:
   Aqueous solutions of acids conduct electricity due to the presence of ions.

   5. Effect on Indicators:
   Acids change blue litmus paper to red and turn methyl orange from yellow to red.

   
   
   

   (j) Mention methods by which acids are prepared.
   
   [2 marks]
   

   Answer

   ×
   

   Methods of Preparing Acids

   Acids can be prepared using several laboratory methods depending on the type of acid required:

   1. Direct Combination:
   Some acids are formed by the direct combination of non-metallic oxides with water.
   Example: SO₃ + H₂O → H₂SO₄

   2. Reaction of Non-metallic Oxides with Water:
   Acidic oxides such as CO₂ and SO₂ dissolve in water to form acids.
   Example: CO₂ + H₂O → H₂CO₃

   3. Action of Acids on Salts:
   A stronger acid can displace a weaker acid from its salt.
   Example: H₂SO₄ + NaCl → HCl + NaHSO₄

   4. Oxidation of Non-Metals:
   Some acids like nitric acid can be prepared by oxidizing ammonia or nitrates in the presence of air and water.

   
   
   

SECTION B

Answer three questions only from this section.

2. (a) The atomic number of element Y is 13.
   
   (i) Write the electron configuration of Y.
   
   (ii) State the:
   
   (I) Group to which Y belongs in the periodic table;
   
   (II) Period to which Y belongs in the periodic table.
   
   (iii) Write the formula of the oxide of Y.
   
   (iv) Name the type of oxide formed by Y.
   
   [6 mark]
   

   Answer

   ×
   

   Properties of Element Y (Atomic Number 13)

   (i) Electron Configuration of Y:
   1s² 2s² 2p⁶ 3s² 3p¹

   (ii) (I) Group:
   
   Group 13 (or IIIA)

   (ii) (II) Period:
   
   Period 3

   (iii) Formula of the Oxide of Y:
   
   Al₂O₃

   (iv) Type of Oxide Formed by Y:
   
   Amphoteric oxide

   
   
   

   (b) (i) Explain the term electrolyte.
   
   [2 mark]
   

   (ii) State three factors that could affect the preferential discharge of ions during electrolysis.
   
   [3 marks]
   

   Answer

   ×
   

   Electrolysis Concepts

   (i) Electrolyte:
   
   An electrolyte is a substance that conducts electricity when molten or dissolved in water by producing ions that move to the electrodes during electrolysis.

   (ii) Factors Affecting Preferential Discharge of Ions:

   1. Position of the ion in the electrochemical series:
   
   Ions lower in the series are more likely to be discharged.
   
   2. Concentration of ions:
   
   If two ions are close in reactivity, the ion with the higher concentration will be discharged preferentially.
   
   3. Nature of the electrode:
   
   Some electrodes (like platinum or carbon) are inert, while reactive electrodes (like copper) can influence which ion is discharged.

   
   
   

   2. (c) In the electrolysis of CuSO₄(aq) using platinum electrodes:
   
   (i) State the substance produced at the:
       (I) Anode;
       (II) Cathode.
   
   (ii) State two effects of the electrolysis on the electrolyte.
   
   [4 marks]
   

   Answer

   ×
   

   Electrolysis of CuSO₄ Solution

   (i) Substances Produced:

   (I) At the Anode: Oxygen gas (O₂)
   (II) At the Cathode: Copper metal (Cu)

   (ii) Effects on the Electrolyte:

   1. The concentration of Cu²⁺ ions in the solution decreases as they are deposited at the cathode.
   
   2. The solution becomes more acidic due to the release of H⁺ ions from the dissociation of water.

   
   
   

   (d) (i) What is global warming?
   
   [2 marks]
   

   (ii) Give two effects of global warming on the environment.
   
   [2 marks]
   

   (iii) State two ways in which global warming could be controlled.
   
   [2 marks]
   

   Answer

   ×
   

   Global Warming

   (i) What is Global Warming?
   
   Global warming is the gradual increase in the Earth's average temperature due to the accumulation of greenhouse gases like carbon dioxide in the atmosphere.

   (ii) Effects of Global Warming on the Environment:

   1. Melting of polar ice caps leading to rising sea levels.
   
   2. Increased frequency of extreme weather events such as floods, droughts, and hurricanes.

   (iii) Ways to Control Global Warming:

   1. Reducing the use of fossil fuels and switching to renewable energy sources like solar and wind.
   
   2. Planting trees and reducing deforestation to absorb carbon dioxide from the atmosphere.
   
   

   
   
   

   (e) Write the chemical equation for the reaction of ethyne with excess:
   
       (i) hydrogen;
       (ii) chlorine.
   
   [4 marks]
   

   Answer

   ×
   

   Reactions of Ethyne

   (i) Reaction of Ethyne with Excess Hydrogen:
   
   C₂H₂ + 2H₂ → C₂H₆
   
   Ethyne is hydrogenated in the presence of a catalyst (usually nickel or platinum) to form ethane.

   (ii) Reaction of Ethyne with Excess Chlorine:
   
   C₂H₂ + 2Cl₂ → C₂H₂Cl₄
   
   Ethyne reacts with excess chlorine to form 1,1,2,2-tetrachloroethane.
   
   

   
   
   

3. (a) Give the general formula of each of the following groups of organic compounds:
   
       (i) Alkanols;
       (ii) Alkanoic acids.
   
   [2 marks]
   

   Answer

   ×
   

   General Formula of Organic Compounds

   (i) Alkanols:
   
   General formula:
   
   C_nH_2n+1OH

   (ii) Alkanoic Acids:
   
   General formula:
   
   C_nH_2n+1COOH

   
   
   

   3. (b) On heating C₁₀H₂₂, it decomposes to octane and an alkene.
   
   (i) Write an equation for the reaction.
   
   [2 marks]
   
   (ii) Name the process involved in 3(b)(i).
   
   [1 mark]
   
   (iii) State two conditions under which the reaction in 3(b)(i) would take place.
   
   [2 marks]
   
   (iv) Which of the products from the reaction in 3(b)(i) would undergo substitution reaction?
   
   [1 mark]
   
   (v) Define the term functional group.
   
   [2 marks]

   Answer

   ×
   

   Hydrocarbon Cracking and Functional Group

   (i) Equation for the reaction:
   
   C₁₀H₂₂ → C₈H₁₈ + C₂H₄

   (ii) Name of the process:
   
   Cracking

   (iii) Conditions for the reaction:
   
   1. High temperature (typically 450–750°C)
   2. Presence of a catalyst such as aluminum oxide or silica

   (iv) Product that undergoes substitution reaction:
   
   Octane (C₈H₁₈)

   (v) Definition of functional group:
   
   A functional group is an atom or group of atoms that gives a compound its characteristic chemical properties and reactions.

   
   
   
   
   

   (c) (i) Complete the table below:
   
   

   Reactants	Formula of Product	IUPAC Name	Type of Bond Formed
   H2 + Na
   H2 + S

   
   [6 marks]
   
   (ii) Give one example each of the following substances:
   
       (I) Acid in the solid state;
       (II) A weak alkali;
       (III) Strong insoluble base;
       (IV) Soluble normal salt whose pH is less than 7.
   
   [4 marks]

   Answer

   ×
   

   Answers to Question 3(c): Chemical Reactions and Examples

   (i) Completed Table:

   Reactants	Formula of Product	IUPAC Name	Type of Bond Formed
   H2 + Na	NaH	Sodium hydride	Ionic bond
   H2 + S	H2S	Hydrogen sulfide	Covalent bond

   
   

   (ii) Examples Of:

   (I) Acid in the solid state:
   
   Oxalic acid (solid acid)

   (II) A weak alkali:
   
   Ammonium hydroxide (weak alkali)

   (III) Strong insoluble base:
   
   Copper(II) oxide (strong insoluble base)

   (IV) Soluble normal salt whose pH is less than 7:
   
   Ammonium chloride (soluble acidic salt)

   
   
   

   (d) A chloride of iron contains 34.2% iron.
   
   Determine its empirical formula.
   [Cl = 35.5, Fe = 56.0]
   
   [5 marks]

   Answer

   ×
   

   Empirical Formula of Iron Chloride

   Given:
   
   The compound contains 34.2% iron (Fe).
   
   Therefore, chlorine (Cl) makes up 100% - 34.2% = 65.8%.

   Step 1: Convert percentages to moles

   • Moles of Fe = 34.2 ÷ 56 = 0.61 mol
   
   
   • Moles of Cl = 65.8 ÷ 35.5 = 1.85 mol

   Step 2: Find the simplest mole ratio

   • Fe:Cl = 0.61 : 1.85
   
   
   • Divide both by 0.61 → Fe:Cl = 1 : 3.03 ≈ 1 : 3

   Conclusion: The empirical formula is FeCl₃.

   
   
   
   

4. (a) (i) List four apparatus used for the preparation of hydrogen.
   
   (ii) Write a balanced chemical reaction equation for the laboratory preparation of hydrogen gas.
   
   (iii) List four properties of hydrogen.
   
   (iv) Give any four uses of hydrogen.
   
   (v) What condition is necessary for a gas to be collected over water?
   
   [15 marks]

   Answer

   ×
   

   Hydrogen: Preparation, Properties, and Uses

   (i) Four apparatus used in the preparation of hydrogen:

   • Conical flask
   • Delivery tube
   • Thistle funnel
   • Water trough

   (ii) Balanced chemical equation:

   Zn + 2HCl → ZnCl₂ + H₂↑

   (iii) Four properties of hydrogen:

   • It is a colourless and odourless gas.
   • It is the lightest gas known.
   • It is insoluble in water.
   • It burns with a pale blue flame to form water.

   (iv) Four uses of hydrogen:

   • Used in the hydrogenation of oils to make margarine.
   • Used as rocket fuel.
   • Used in the production of ammonia (Haber process).
   • Used as a reducing agent in metallurgy.

   (v) Condition necessary for a gas to be collected over water:

   The gas must be insoluble or slightly soluble in water.

   
   

   (b) (i) Explain why graphite is used as a lubricant.
   
   (ii) Describe what would be observed when some piece of sodium is dropped unto the surface of cold water.
   
   (iii) Write an equation for the reaction between sodium and water.
   
   [7 marks]

   Answer

   ×
   

   Properties and Reaction of Graphite and Sodium

   (i) Why graphite is used as a lubricant:

   Graphite is used as a lubricant because it has a layered structure where layers can slide over each other easily due to weak van der Waals forces between them. This allows it to reduce friction effectively.

   (ii) Observation when sodium is dropped into cold water:

   • Sodium melts into a silvery ball and darts around on the water surface.
   • A hissing sound is heard as hydrogen gas is released.
   • The solution becomes alkaline and may turn red litmus paper blue.
   • A small explosion or flame may occur if the reaction is vigorous enough.

   (iii) Chemical equation for the reaction:

   2Na + 2H₂O → 2NaOH + H₂↑

   
   

   (c) Name the drying agents for the following gases:
   
   (i) Ammonia;
   (ii) Hydrogen;
   (iii) Sulphur (IV) oxide.
   
   [3 marks]

   Answer

   ×
   

   Drying Agents for Gases

   (i) Ammonia:
   
   Drying agent: Quicklime (CaO)
   
   Note: Concentrated sulfuric acid and anhydrous calcium chloride are not used because they react with ammonia.

   (ii) Hydrogen:
   
   Drying agent: Anhydrous calcium chloride (CaCl₂) or concentrated sulfuric acid (H₂SO₄)

   (iii) Sulphur (IV) oxide (SO₂):
   
   Drying agent: Concentrated sulfuric acid (H₂SO₄)
   
   Note: Anhydrous calcium chloride is not ideal because it may absorb SO₂.

   
   

5. (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.
   
   [10 marks]

   Answer

   ×
   

   Balanced Chemical Equations

   (i) Ammonia gas with copper(II) oxide:
   
   2NH₃ + 3CuO → 3Cu + 3H₂O + N₂

   (ii) Ammonia gas with oxygen gas:
   
   4NH₃ + 3O₂ → 2N₂ + 6H₂O

   (iii) Aqueous potassium iodide with chlorine gas:
   
   Cl₂ + 2KI → 2KCl + I₂

   (iv) Iron with dilute tetraoxosulphate(VI) acid:
   
   Fe + H₂SO₄ → FeSO₄ + H₂↑

   (v) Aqueous lead(II) trioxonitrate(V) with hydrogen chloride gas:
   
   Pb(NO₃)₂ + 2HCl → PbCl₂↓ + 2HNO₃
   
   
   

   (b) Describe briefly the process involved in the extraction of tin from tin ore.
   
   [5 marks]

   Answer

   ×
   

   Extraction of Tin from Tin Ore

   The extraction of tin from its main ore, cassiterite (SnO₂), involves the following steps:

   1. Concentration:
   
   The ore is crushed and washed to remove impurities such as sand and clay.

   2. Roasting:
   
   The concentrated ore is heated in the presence of air to remove volatile impurities like sulphur and arsenic.

   3. Reduction:
   
   The roasted ore is then mixed with carbon (usually coke) and heated in a furnace. The carbon reduces SnO₂ to tin metal.
   SnO₂ + 2C → Sn + 2CO

   4. Purification:
   
   The crude tin obtained is purified by liquation (melting at low temperature) or electrolytic refining to remove remaining impurities.

   
   
   
   
   

   5. (c) State the class of oxide to which each of the following compounds belong:
   
   (i) Na₂O;
   (ii) ZnO;
   (iii) SO₂;
   (iv) CO₂;
   (v) N₂O.
   
   [5 marks]

   Answer

   ×
   

   Classes of Oxides

   (i) Na₂O: Basic oxide

   (ii) ZnO: Amphoteric oxide

   (iii) SO₂: Acidic oxide

   (iv) CO₂: Acidic oxide

   (v) N₂O: Neutral oxide

   5. (d) (i) Name two gases which can be used to demonstrate the fountain experiment.
   
   [2 marks]

   Answer

   ×
   

   Gases Used in Fountain Experiment

   1. Ammonia (NH₃)

   2. Hydrogen chloride (HCl)

   (ii) Give the components of the following alloys:
   
   (I) Brass;
   (II) Bronze;
   (III) Steel.
   
   [3 marks]

   Answer

   ×
   

   Components of Alloys

   (I) Brass: Copper (Cu) and Zinc (Zn)

   (II) Bronze: Copper (Cu) and Tin (Sn)

   (III) Steel: Iron (Fe) and Carbon (C)

END OF PAPER