Inorganic Chemistry
7 marks · EasyThis question is about carbon dioxide and redox reactions.
Write the word equation and the balanced symbol equation for the thermal decomposition of copper(II) carbonate.
State the products formed when copper(II) carbonate is heated.
Explain, in terms of electron transfer, which substance is reduced in the extraction of copper from copper(II) oxide using carbon.
Write the half-equation for the reduction of copper(II) ions to copper atoms.
Identify the reducing agent in the reaction between copper(II) oxide and carbon and explain your answer.
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(a) Word: copper(II) carbonate → copper(II) oxide + carbon dioxide Symbol: CuCO3(s) → CuO(s) + CO2(g)
(b) Copper(II) oxide and carbon dioxide.
(c) Copper(II) ions are reduced because they gain electrons from carbon to become copper atoms.
(d) Cu^2+ + 2e⁻ → Cu
(e) Carbon is the reducing agent because it donates electrons to copper(II) ions or removes oxygen from copper(II) oxide.
Common mistakes: Forgot state symbols; Incorrect charge on ions; Mixing up reduction and oxidation
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Marking points
B1 (a) · 1 mark · Correct word equation
B2 (a) · 1 mark · Correct balanced symbol equation
B3 (b) · 1 mark · Correctly identifies both products
M1 (c) · 1 mark · Correct identification of species reduced
M2 (c) · 1 mark · Appropriate explanation using electron gain
B4 (d) · 1 mark · Correct half-equation (Cu^2+ + 2e⁻ → Cu)
B5 (e) · 1 mark · Correct identification of reducing agent and valid explanation
Worked solution
a) Word: copper(II) carbonate → copper(II) oxide + carbon dioxide Symbol: CuCO3(s) → CuO(s) + CO2(g)
b) Copper(II) oxide and carbon dioxide are formed.
c) Copper(II) ions, Cu^2+, are reduced to copper atoms. Reduction is gain of electrons: the Cu^2+ ions gain two electrons from carbon to become Cu.
d) Cu^2+ + 2e⁻ → Cu
e) Carbon is the reducing agent; it donates electrons to the copper(II) ions, allowing their reduction to copper metal, or it removes oxygen from copper(II) oxide.