Question

3(c) Study the diagram below and answer the questions that follow.
(i) What is the set-up used for?
(ii) Mention two compounds that could be used as electrolytes in the cell.
(iii) Write a half-cell equation for the reaction at the anode.
(iv) Calculate the electrochemical equivalent of copper if the cathode gained mass of 3.2g when 50 amperes of current was passed for 3 minutes 13 seconds.

Accepted Answer

(i) The set-up is used for the purification of copper metal, or electroplating/extraction of copper by electrolysis.

(ii) Compounds that could be used as electrolytes in the cell: Copper (II) tetraoxosulphate (VI) [CuSO4(aq)]; Copper (II) trioxonitrate (V) [Cu(NO3)2(aq)]; Copper (II) chloride [CuCl2(aq)].

(iii) Anodic half-cell equation: Cu(s) → Cu²⁺(aq) + 2e⁻

(iv) Given: m = mass deposited = 3.2g, t = time = 3min 13sec = (3×60+13) = 193 seconds, I = current = 50A.
Electrochemical equivalent, z = m/(It) = 3.2/(50×193) = 3.2/9650 ≈ 3.32×10⁻⁴ g/C.

WAEC Chemistry 2022 Theory — Question 5

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