Question

With respect to the electrolysis of copper (II) sulphate solution using copper electrodes, which statement is correct?

• A. Copper metal is deposited at the negative electrode.
• B. Oxygen gas is produced at the positive electrode.
• C. The positive electrode increases in mass.
• D. The negative electrode decreases in mass.

Hint:

In this process, the blue color of the CuSO_4 solution does not fade because the number of Cu^2+ ions leaving the solution at the cathode is replenished by the anode!

Answer 1

The Correct Option is A

To address the question regarding the electrolysis of copper (II) sulphate solution using copper electrodes, let us understand the process and its effects at both the anode (positive electrode) and cathode (negative electrode).

Process of Electrolysis

During the electrolysis of copper (II) sulphate solution:

• The cathode, which is the negative electrode, attracts the Cu²⁺ ions from the solution. These copper ions gain electrons (reduction process) and are deposited as copper metal on the cathode. This is why the statement "Copper metal is deposited at the negative electrode" is correct.
• The anode, which is the positive electrode, facilitates the oxidation process. Copper metal from the anode dissolves into the solution as Cu²⁺ ions, thus causing the anode to lose mass. Therefore, the statement "The positive electrode increases in mass" is incorrect.
• At the anode, instead of producing oxygen gas, copper metal is oxidized to form copper ions. Therefore, "Oxygen gas is produced at the positive electrode" is incorrect.
• The statement "The negative electrode decreases in mass" is incorrect because copper is deposited here, increasing its mass.

In conclusion, the only correct statement concerning the electrolysis of copper (II) sulphate solution using copper electrodes is: Copper metal is deposited at the negative electrode.

Here is a simplified representation of the reactions occurring:

• At the cathode (reduction): \(Cu^{2+} + 2e^- → Cu_{(s)}\)
• At the anode (oxidation): \(Cu_{(s)} → Cu^{2+} + 2e^-\)

These reactions ensure the mass of the cathode increases due to deposition of copper, while the anode loses mass as copper dissolves into the solution.