ICSE Class 10 Chemistry Board Exam Question Paper 2017 with Solutions

ICSE Class 10 Chemistry Board Exam Question Paper 2017 with Solutions

SECTION I [40 Marks]

(Attempt all questions from this Section)

Question 1.

(a) Fill in the blanks from the choices given in brackets: [5]
(i) The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion is called .......... (electron affinity, ionisation potential, electronegativity)
(ii) The compound that does not have a lone pair of electrons is (water, ammonia, carbon tetrachloride)
(iii) When a metallic oxide is dissolved in water, the solution formed has a high concentration of ions. (H⁺, H₃O⁺, OH^-)
(iv) Potassium sulphite on reacting with hydrochloric acid releases .......... gas. (Cl₂, SO₂, H₂S)
(v) The compound formed when ethene reacts with Hydrogen is .......................... (CH₄, C₂H₆, C₃H₈)

Answer:
(i) ionisation potential
(ii) carbon tetrachloride
(iii) OH^-
(iv) SO₂
(v) C₂H₆

Teacher's Note:
a) Ionisation potential increases across a period and decreases down a group due to nuclear charge and atomic size.
b) Students often confuse hydroxide ions with hydronium ions when dealing with metallic oxides versus non-metallic oxides.

(b) Choose the correct answer from the options given below: [5]
(i) A chloride which forms a precipitate that is soluble in excess of ammonium hydroxide, is:
1. Calcium chloride
2. Ferrous chloride
3. Ferric chloride
4. Copper chloride
(ii) If the molecular formula of an organic compound is C₁₀H₁₈ it is:
1. alkene
2. alkane
3. alkyne
4. Not a hydrocarbon
(iii) Which of the following is a common characteristic of a covalent compound?
1. high melting point
2. consists of molecules
3. always soluble in water
4. conducts electricity when it is in the molten state
(iv) To increase the pH value of a neutral solution, we should add:
1. an acid
2. an acid salt
3. an alkali
4. a salt
(v) Anhydrous iron(III) chloride is prepared by:
1. direct combination
2. simple displacement
3. decomposition
4. neutralization

Answer:
(i) 4. Copper chloride
(ii) 3. alkyne
(iii) 2. consists of molecules
(iv) 3. an alkali
(v) 1. direct combination

Teacher's Note:
a) For C_nH_2n-2 general formula, C₁₀H₁₈ corresponds to an alkyne.
b) Anhydrous iron(III) chloride is formed by passing dry chlorine gas over heated iron.

(c) Identify the substance underlined, in each of the following cases: [5]
(i) Cation that does not form a precipitate with ammonium hydroxide but forms one with sodium hydroxide.
(ii) The electrolyte used for electroplating an article with silver.
(iii) The particles present in a liquid such as kerosene, that is a non electrolyte.
(iv) An organic compound containing – COOH functional group.
(v) A solid formed by reaction of two gases, one of which is acidic and the other basic in nature.

Answer:
(i) Copper
(ii) Sodium argento cyanide
(iii) molecules
(iv) Carboxylic acid
(v) Ammonium chloride

Teacher's Note:
a) Copper hydroxide is precipitated by NaOH but dissolves in excess NH₄OH to form a deep blue solution, hence no precipitate remains.
b) Non-electrolytes consist purely of molecules and do not dissociate into ions.

(d) Write a balanced chemical equation for each of the following: [5]
(i) Action of cold and dilute Nitric acid on Copper.
(ii) Reaction of Ammonia with heated copper oxide.
(iii) Preparation of methane from iodomethane.
(iv) Action of concentrated sulphuric acid on Sulphur.
(v) Laboratory preparation of ammonia from ammonium chloride.

Answer:
(i) \( 3\text{Cu} + 8\text{HNO}_{3} \rightarrow 3\text{Cu}(\text{NO}_{3})_{2} + 4\text{H}_{2}\text{O} + 2\text{NO}\uparrow \)
(ii) \( 2\text{NH}_{3} + 3\text{CuO} \rightarrow 3\text{Cu} + 3\text{H}_{2}\text{O} + \text{N}_{2}\uparrow \)
(iii) \( \text{CH}_{3}\text{I} + 2[\text{H}] \rightarrow \text{CH}_{4} + \text{HI} \)
(iv) \( \text{S} + 2\text{H}_{2}\text{SO}_{4} \rightarrow 3\text{SO}_{2} + 2\text{H}_{2}\text{O} \)
(v) \( 2\text{NH}_{4}\text{Cl} + \text{Ca}(\text{OH})_{2} \rightarrow \text{CaCl}_{2} + 2\text{H}_{2}\text{O} + 2\text{NH}_{3} \)

Teacher's Note:
a) Ensure all chemical equations are fully balanced and include physical state arrows where appropriate.
b) Nascent hydrogen reduction of iodomethane yields methane and hydrogen iodide.

(e) State one relevant observation for each of the following reactions: [5]
(i) Addition of ethyl alcohol to acetic acid in the presence of concentrated Sulphuric acid.
(ii) Action of dilute Hydrochloric acid on iron (II) sulphide.
(iii) Action of Sodium hydroxide solution on ferrous sulphate solution.
(iv) Burning of ammonia in air.
(v) Action of concentrated Sulphuric acid on hydrated copper sulphate.

Answer:
(i) Fruity smell due to the formation of ester is observed.
(ii) A gas with a rotten egg smell (hydrogen sulphide) evolves.
(iii) Dirty green precipitate of ferrous hydroxide is formed.
(iv) Yellowish green flame is produced when ammonia burns in air.
(v) Hydrated copper sulphate which is blue in colour changes to anhydrous copper sulphate which is white.

Teacher's Note:
a) Esterification produces a characteristic pleasant sweet or fruity odour.
b) Dehydration of blue copper vitriol turns it into a white amorphous powder.

(f) (i) Draw the structural formula for each of the following: [5]
1. 2, 3 – dimethyl butane
2. diethyl ether
3. propanoic acid
(ii) From the list of terms given, choose the most appropriate term to match the given description.
(calcination, roasting, pulverisation, smelting)
1. Crushing of the ore into a fine powder.
2. Heating of the ore in the absence of air to a high temperature.

Answer:
(i) 1. 2, 3 – dimethyl butane:
\( \text{CH}_{3} - \text{CH}(\text{CH}_{3}) - \text{CH}(\text{CH}_{3}) - \text{CH}_{3} \)
2. diethyl ether:
\( \text{C}_{2}\text{H}_{5} - \text{O} - \text{C}_{2}\text{H}_{5} \)
3. propanoic acid:
\( \text{CH}_{3} - \text{CH}_{2} - \text{COOH} \)
(ii) 1. Pulverisation
2. Calcination

Teacher's Note:
a) Structural formulas must show all covalent bonds clearly between carbon, hydrogen, and oxygen atoms.
b) Calcination is strictly defined as heating an ore in the absence or limited supply of air.

(g) (i) Calculate the number of gram atoms in 4.6 grams of sodium (Na = 23). [5]
(ii) Calculate the percentage of water of crystallization in CuSO₄.5H₂O (H = 1, O = 16, S = 32, Cu = 64)
(iii) A compound of X and Y has the empirical formula XY₂. Its vapour density is equal to its empirical formula weight. Determine its molecular formula.

Answer:
(i) Number of gram atoms in sodium = \( \frac{\text{Given mass}}{\text{Atomic mass}} = \frac{4.6}{23} = 0.2 \) gram atoms.
(ii) Molecular mass of \( \text{CuSO}_{4}.5\text{H}_{2}\text{O} = 64 + 32 + (4 \times 16) + 5(2 \times 1 + 16) = 64 + 32 + 64 + 90 = 250 \, \text{g/mol} \)
Mass of water of crystallization = \( 90 \, \text{g} \)
Percentage of water = \( \frac{90}{250} \times 100 = 36\% \)
(iii) Empirical formula = \( \text{XY}_{2} \)
Molecular mass = \( 2 \times \text{Vapour Density} = 2 \times \text{Empirical formula weight} \)
Therefore, \( n = \frac{\text{Molecular mass}}{\text{Empirical formula weight}} = 2 \)
Molecular formula = \( (\text{Empirical formula})_{n} = (\text{XY}_{2})_{2} = \text{X}_{2}\text{Y}_{4} \)

Teacher's Note:
a) Gram atoms represent moles of atoms for monatomic elements like sodium.
b) Vapour density relation to molecular mass is given by the standard formula \( \text{Molecular Mass} = 2 \times \text{Vapour Density} \).

(h) Match the atomic number 2, 4, 8, 15, and 19 with each of the following: [5]
(i) A solid non-metal belonging to the third period.
(ii) A metal of valency 1.
(iii) A gaseous element with valency 2.
(iv) An element belonging to Group 2.
(v) A rare gas.

Answer:
(i) 15
(ii) 19
(iii) 8
(iv) 4
(v) 2

Teacher's Note:
a) Atomic number 15 is Phosphorus (solid non-metal, Period 3, Group 15).
b) Atomic number 19 is Potassium (metal with 1 valence electron, Group 1).

SECTION II [40 Marks]

Attempt any four questions from this Section

Question 2.

(a) Arrange the following as per the instruction given in the brackets:
(i) He, Ar, Ne (Increasing order of the number of electron shells)
(ii) Na, Li, K (Increasing Ionisation Energy)
(iii) F, Cl, Br (Increasing electronegativity)
(iv) Na, K, Li (Increasing atomic size)

Answer:
(i) He < Ne < Ar (1 shell, 2 shells, 3 shells)
(ii) K < Na < Li (Ionisation energy decreases down the group)
(iii) Br < Cl < F (Electronegativity decreases down the group)
(iv) Li < Na < K (Atomic size increases down the group)

Teacher's Note:
a) Trends in periodic properties follow atomic number and shell count modifications across periods and groups.
b) Check the inequality signs carefully when arranging in increasing order.

(b) State the type of Bonding in the following molecules: [2]
(i) Water
(ii) Calcium oxide

Answer:
(i) Covalent bonding
(ii) Ionic bonding

Teacher's Note:
a) Water involves sharing of electron pairs between non-metal atoms (hydrogen and oxygen).
b) Calcium oxide involves complete transfer of electrons between a metal and a non-metal.

(c) Answer the following questions: [2]
(i) How will you distinguish between Ammonium hydroxide and Sodium hydroxide using copper sulphate solution?
(ii) How will you distinguish between dilute hydrochloric acid and dilute sulphuric acid using lead nitrate solution ?

Answer:

Answer for (ii):
Dilute hydrochloric acid gives a white precipitate of lead chloride with lead nitrate solution which is soluble on heating, whereas dilute sulphuric acid gives a heavy white precipitate of lead sulphate with lead nitrate solution which is insoluble even on heating.

Teacher's Note:
a) Complex ion formation occurs with excess ammonium hydroxide giving tetraamminecopper(II) complex.
b) Lead sulphate is insoluble in water and dilute acids.

(d) Identify the salts P and Q from the observations given below: [2]
(i) On performing the flame test salt P produces a lilac coloured flame and its solution gives a white precipitate with silver nitrate solution, which is soluble in Ammonium hydroxide solution.
(ii) When dilute HCl is added to a salt Q, a brisk effervescence is produced and the gas turns lime water milky. When NH₄OH solution is added to the above mixture (after adding dilute HCl), it produces a white precipitate which is soluble in excess NH₄OH solution.

Answer:
(i) P is Potassium chloride (\(\text{KCl}\))
(ii) Q is Zinc carbonate (\(\text{ZnCO}_{3}\))

Teacher's Note:
a) Lilac flame is characteristic of potassium cations.
b) Zinc carbonate reacts with HCl to liberate carbon dioxide gas which turns lime water milky.

Question 3.

(a) Draw an electron dot diagram to show the formation of each of the following compounds: [4]
(i) Methane
(ii) Magnesium Chloride [H = 1, C = 6, Mg = 12, Cl = 17]

Answer:
(i) Methane (\(\text{CH}_{4}\)): Carbon shares four electron pairs with four hydrogen atoms to achieve a stable octet.
(ii) Magnesium Chloride (\(\text{MgCl}_{2}\)): Magnesium transfers its two valence electrons to two chlorine atoms, forming \(\text{Mg}^{2+}\) and two \(\text{Cl}^{-}\) ions held by electrostatic forces of attraction.

Teacher's Note:
a) Use dots and crosses clearly to distinguish between electrons of different atoms.
b) For ionic compounds, show charges on the resulting ions in brackets.

(b) State the observations at the anode and at the cathode during the electrolysis of: [4]
(i) fused lead bromide using graphite electrodes.
(ii) copper sulphate solution using copper electrodes.

Answer:
(i) At anode: Dark reddish brown fumes of bromine evolve. At cathode: Greyish white metal lead is deposited.
(ii) At anode: The copper anode decreases in mass due to dissolution of copper atoms into copper ions. At cathode: Reddish-brown copper metal is deposited.

Teacher's Note:
a) In molten lead bromide electrolysis, active halogen gas is liberated at the inert anode.
b) In copper electrorefining with active copper electrodes, the anode ionizes while the cathode accumulates pure copper.

(c) Select the ion in each case, that would get selectively discharged from the aqueous mixture of the ions listed below: [2]
(i) \(\text{SO}_{4}^{2-}\), \(\text{NO}_{3}^{-}\) and \(\text{OH}^{-}\)
(ii) \(\text{Pb}^{2+}\), \(\text{Ag}^{+}\) and \(\text{Cu}^{2+}\)

Answer:
(i) \(\text{OH}^{-}\)
(ii) \(\text{Ag}^{+}\)

Teacher's Note:
a) Hydroxide ion is lower in the electrochemical series of anions and gets discharged preferentially.
b) Silver ion is lower in the electrochemical series of cations compared to lead and copper.

Question 4.

(a) Certain blank spaces are left in the following table and these are labelled as A, B, C, D and E. Identify each of them. [5]

Answer:
A -> Below 200°C: Sodium hydrogen sulphate (\(\text{NaHSO}_{4}\)); Above 200°C: Sodium sulphate (\(\text{Na}_{2}\text{SO}_{4}\))
B -> Upward displacement of air
C -> Magnesium nitride (\(\text{Mg}_{3}\text{N}_{2}\)) and water (\(\text{H}_{2}\text{O}\))
D -> Calcium oxide (\(\text{CaO}\))
E -> Downward displacement of air

Teacher's Note:
a) Hydrogen chloride gas is denser than air and is collected by upward displacement of air.
b) Ammonia is alkaline and less dense than air, hence dried using basic quicklime and collected by downward displacement of air.

(b) Write balanced chemical equations to show: [3]
(i) The oxidizing action of conc. Sulphuric acid on Carbon.
(ii) The behaviour of \(\text{H}_{2}\text{SO}_{4}\) as an acid when it reacts with Magnesium.
(iii) The dehydrating property of conc. Sulphuric acid with sugar.

Answer:
(i) \( \text{C} + 2\text{H}_{2}\text{SO}_{4} \rightarrow \text{CO}_{2} + 2\text{H}_{2}\text{O} + 2\text{SO}_{2}\uparrow \)
(ii) \( \text{Mg} + \text{H}_{2}\text{SO}_{4} \rightarrow \text{MgSO}_{4} + \text{H}_{2}\uparrow \)
(iii) \( \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_{2}\text{SO}_{4} \rightarrow 12\text{C} + 11\text{H}_{2}\text{O} + [\text{H}_{2}\text{SO}_{4}.11\text{H}_{2}\text{O}] \)

Teacher's Note:
a) Concentrated sulphuric acid acts as a strong oxidizing agent when reacting with non-metals like carbon.
b) Dehydration of sucrose leaves a spongy black mass of carbon.

(c) Write balanced chemical equations to show how \(\text{SO}_{3}\) is converted to Sulphuric acid in the contact process. [2]

Answer:
\( \text{SO}_{3} + \text{H}_{2}\text{SO}_{4} \rightarrow \text{H}_{2}\text{S}_{2}\text{O}_{7} \) (Oleum)
\( \text{H}_{2}\text{S}_{2}\text{O}_{7} + \text{H}_{2}\text{O} \rightarrow 2\text{H}_{2}\text{SO}_{4} \)

Teacher's Note:
a) Direct dissolution of sulphur trioxide in water is highly exothermic and forms a dense mist, hence it is dissolved in concentrated sulphuric acid first.
b) Dilution of oleum with calculated water yields pure commercial sulphuric acid.

Question 5.

(a) (i) Propane burns in air according to the following equation: [4]
\(\text{C}_{3}\text{H}_{8} + 5\text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}\).
What volume of propane is consumed on using \(1000 \, \text{cm}^{3}\) of air, considering only 20% of air contains oxygen?
(ii) The mass of 11.2 litres of a certain gas at s.t.p. is 24g. Find the gram molecular mass of the gas.

Answer:
(i) Volume of air = \(1000 \, \text{cm}^{3}\)
Volume of oxygen in \(1000 \, \text{cm}^{3}\) of air = \(20\% \text{ of } 1000 = 200 \, \text{cm}^{3}\)
From the equation, \(5 \, \text{volumes of } \text{O}_{2}\) react with \(1 \, \text{volume of } \text{C}_{3}\text{H}_{8}\).
Therefore, volume of propane consumed = \( \frac{200}{5} = 40 \, \text{cm}^{3} \).
(ii) Volume of gas at s.t.p. = \(11.2 \, \text{litres}\)
Mass of \(11.2 \, \text{litres}\) = \(24 \, \text{g}\)
Mass of \(22.4 \, \text{litres}\) (Gram molecular mass) = \(24 \times 2 = 48 \, \text{g/mol}\).

Teacher's Note:
a) Apply Gay-Lussac's Law of Combining Volumes directly to stoichiometric coefficients.
b) Gram molecular mass is the mass occupied by 22.4 litres of any gas at standard temperature and pressure.

(b) A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure: [4]
(i) Find the number of moles of hydrogen present.
(ii) What weight of \(\text{CO}_{2}\) can the cylinder hold under similar conditions of temperature and pressure? (\(\text{H} = 1, \text{C} = 12, \text{O} = 16\))
(iii) If the number of molecules of hydrogen in the cylinder is X, calculate the number of \(\text{CO}_{2}\) molecules in the cylinder under the same conditions of temperature and pressure.
(iv) State the law that helped you to arrive at the above result.

Answer:
(i) Mass of hydrogen = \(1000 \, \text{g}\). Molar mass of \(\text{H}_{2} = 2 \, \text{g/mol}\).
Number of moles = \( \frac{1000}{2} = 500 \, \text{moles} \).
(ii) Under similar conditions, the cylinder holds 500 moles of \(\text{CO}_{2}\) as well.
Molar mass of \(\text{CO}_{2} = 12 + (2 \times 16) = 44 \, \text{g/mol}\).
Weight of \(\text{CO}_{2} = 500 \times 44 = 22,000 \, \text{g} = 22 \, \text{kg}\).
(iii) Number of \(\text{CO}_{2}\) molecules = X.
(iv) Avogadro's Law.

Teacher's Note:
a) Equal volumes of all gases under identical conditions of temperature and pressure contain equal number of molecules.
b) Mole concept calculations must include correct units for mass and moles.

(c) Write a balanced chemical equation for the preparation of each of the following salts: [2]
(i) Copper carbonate
(ii) Ammonium sulphate crystals

Answer:
(i) \( \text{Cu}(\text{NO}_{3})_{2} + \text{Na}_{2}\text{CO}_{3} \rightarrow \text{CuCO}_{3}\downarrow + 2\text{NaNO}_{3} \)
(ii) \( 2\text{NH}_{4}\text{OH} + \text{H}_{2}\text{SO}_{4} \rightarrow (\text{NH}_{4})_{2}\text{SO}_{4} + 2\text{H}_{2}\text{O} \)

Teacher's Note:
a) Insoluble salts like copper carbonate are prepared by precipitation (double displacement).
b) Soluble salts like ammonium sulphate can be prepared by neutralization of an alkali with an acid.

Question 6.

(a) Give a balanced chemical equation for each of the following: [4]
(i) Action of conc. Nitric acid on Sulphur.
(ii) Catalytic oxidation of Ammonia.
(iii) Laboratory preparation of Nitric acid.
(iv) Reaction of Ammonia with Nitric acid.

Answer:
(i) \( \text{S} + 6\text{HNO}_{3}(\text{conc.}) \rightarrow \text{H}_{2}\text{SO}_{4} + 6\text{NO}_{2} + 2\text{H}_{2}\text{O} \)
(ii) \( 4\text{NH}_{3} + 5\text{O}_{2} \xrightarrow[800^{\circ}\text{C}]{\text{Pt}} 4\text{NO} + 6\text{H}_{2}\text{O} + \text{Heat} \)
(iii) \( \text{NaNO}_{3} + \text{H}_{2}\text{SO}_{4}(\text{conc.}) \xrightarrow{\text{below } 200^{\circ}\text{C}} \text{NaHSO}_{4} + \text{HNO}_{3} \)
(iv) \( \text{NH}_{3} + \text{HNO}_{3} \rightarrow \text{NH}_{4}\text{NO}_{3} \)

Teacher's Note:
a) Platinum catalyst is essential for the oxidation of ammonia to nitric oxide.
b) Temperature must be maintained below 200°C in the laboratory preparation of nitric acid to prevent damage to glassware and decomposition of nitric acid.

(b) Identify the term or substance based on the descriptions given below: [4]
(i) Ice like crystals formed on cooling an organic acid sufficiently.
(ii) Hydrocarbon containing a triple bond used for welding purposes.
(iii) The property by virtue of which the compound has the same molecular formula but different structural formulae.
(iv) The compound formed where two alkyl groups are linked by carbonyl group.

Answer:
(i) Glacial acetic acid
(ii) Acetylene (Ethyne)
(iii) Isomerism
(iv) Ketone

Teacher's Note:
a) Pure acetic acid solidifies into ice-like crystals at temperatures below 16.6°C.
b) Isomerism explains the existence of compounds with identical molecular formulas but distinct structural arrangements.

(c) Give a balanced chemical equation for each of the following: [2]
(i) Preparation of ethane from Sodium propionate.
(ii) Action of alcoholic KOH on bromoethane.

Answer:
(i) \( \text{C}_{2}\text{H}_{5}\text{COONa} + \text{NaOH} \xrightarrow{\text{CaO}, \Delta} \text{C}_{2}\text{H}_{6} + \text{Na}_{2}\text{CO}_{3} \)
(ii) \( \text{CH}_{3}\text{CH}_{2}\text{Br} + \text{KOH}(\text{alc.}) \rightarrow \text{CH}_{2} = \text{CH}_{2} + \text{KBr} + \text{H}_{2}\text{O} \)

Teacher's Note:
a) Decarboxylation of sodium propionate with soda lime produces ethane.
b) Reaction of alcoholic potassium hydroxide with bromoethane is a dehydrohalogenation reaction yielding ethene.

Question 7.

(a) Name the following: [4]
(i) The process of coating of iron with zinc.
(ii) An alloy of lead and tin that is used in electrical circuits.
(iii) An ore of zinc containing its sulphide.
(iv) A metal oxide that can be reduced by hydrogen.

Answer:
(i) Galvanisation
(ii) Solder
(iii) Zinc blende (Sphalerite)
(iv) Copper oxide

Teacher's Note:
a) Galvanisation prevents rusting of iron by providing a protective zinc coating.
b) Solder has a low melting point making it ideal for joining electrical wires.

(b) Answer the following questions with respect to the electrolytic process in the extraction of aluminum: [2]
(i) Identify the components of the electrolyte other than pure alumina and the role played by each.
(ii) Explain why powdered coke is sprinkled over the electrolytic mixture.

Answer:
(i) Cryolite (\(\text{Na}_{3}\text{AlF}_{6}\)): Acts as a solvent and lowers the fusion temperature from 2050°C to 950°C. Fluorspar (\(\text{CaF}_{2}\)): Increases the electrical conductivity of the electrolytic mixture.
(ii) Powdered coke is sprinkled over the surface to prevent heat loss by radiation and to prevent the burning of carbon anodes in air.

Teacher's Note:
a) Pure alumina is a bad conductor of electricity and has a very high melting point.
b) Hall-Heroult's process relies heavily on cryolite and fluorspar mixture for economic viability.

(c) Complete the following by selecting the correct option from the choices given: [3]
(i) The metal which does not react with water or dilute \(\text{H}_{2}\text{SO}_{4}\) but reacts with concentrated \(\text{H}_{2}\text{SO}_{4}\) is (\(\text{Al} / \text{Cu} / \text{Zn} / \text{Fe}\))
(ii) The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction (\(\text{Fe} / \text{Mg} / \text{Pb} / \text{Al}\))
(iii) The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is (\(\text{Al} / \text{Na} / \text{Mg} / \text{K}\))

Answer:
(i) \(\text{Cu}$ (the marking scheme also accepts option \(\text{Cu}\))
(ii) \(\text{Pb}$
(iii) \(\text{Mg}$

Teacher's Note:
a) Copper is less reactive than hydrogen and does not displace it from dilute acids.
b) Lead oxide is amphoteric and can be successfully reduced using carbon (coke) in smelting.