For what time t during the electrolysis of an aqueous solution of CuCl2

For what time t during the electrolysis of an aqueous solution of CuCl2, the cathode will release m = 4.74 if the current is l = 2A.

The mass of the substance released at the cathode during electrolysis during the time t of passing the electric current through the solution, with the force I, is found according to the Faraday law: m = k ∙ I ∙ t, where k is the electrochemical equivalent of the substance. Then:

t = m: (k ∙ I).

From the condition of the problem it is known that a current l = 2 A flows through the electrolyte, and m = 4.74 g = 0.00474 kg of copper was released at the cathode. The electrochemical equivalent of copper is k = 0.329 ∙ 10 ^ (- 6) kg / C (since the valence of copper in copper chloride CuCl₂ is 2). Substitute the values ​​of the quantities into the calculation formula:

t = 0.00474 kg: (0.329 ∙ 10 ^ (- 6) kg / C ∙ 2 A);

t = 7204 s ≈ 2 h.

Answer: in 2 hours.