What will happen during the electrolysis of aqueous solution of \(CuSO_4\) by using platinum electrodes?

A. Copper will deposit at cathode

B. Copper will deposit at anode

C. Oxygen will be released at anode

D. Copper will dissolve at anode

Choose the correct answer from the options given below:

A and C only

The correct answer is option 2. A and C only.

Let us explore the electrolysis of an aqueous solution of \(CuSO_4\) using platinum electrodes:

Electrolysis Setup

Solution: \(CuSO_4\) (Copper(II) sulfate) in water.

Electrodes: Platinum electrodes.

Electrolysis Reactions

At the Cathode (Negative Electrode):

Reduction Reaction:

In the aqueous solution of \(CuSO_4\), the primary reduction reaction at the cathode involves copper(II) ions:

\(\text{Cu}^{2+} (aq) + 2e^- \longrightarrow \text{Cu} (s)\)

Copper ions (\(\text{Cu}^{2+}\)) in the solution gain electrons and are reduced to solid copper metal, which deposits on the cathode. This is because the reduction of copper ions to copper metal has a more favorable electrode potential compared to the reduction of water to hydrogen gas in this context.

At the Anode (Positive Electrode):

Oxidation Reactions:

In an aqueous solution, water can be oxidized to produce oxygen gas:

\(2\text{H}_2\text{O} (l) \longrightarrow O_2 (g) + 4H^+ (aq) + 4e^-\)

This reaction occurs because the oxidation of water to oxygen is energetically more favorable compared to the oxidation of copper metal to copper(II) ions, especially given that platinum electrodes do not participate in the oxidation reaction themselves. If copper were used as the anode, the reaction would be:

\(\text{Cu} (s) \longrightarrow \text{Cu}^{2+} (aq) + 2e^-\)

This would result in copper dissolving into the solution. However, with platinum electrodes, this dissolution does not happen; instead, oxygen gas is generated.

Summary of Electrolysis Process:

At the Cathode: Copper ions (\(\text{Cu}^{2+}\)) in the solution gain electrons and are reduced to solid copper. This solid copper deposits on the cathode.

At the Anode: Water is oxidized to produce oxygen gas and protons (\(H^+\)). The oxygen gas bubbles up and is released from the anode.

Why These Reactions Occur:

Electrode Potentials: The standard electrode potential for the reduction of copper ions to copper metal (\(E^\circ = +0.34\) V) is more positive than that for the reduction of water to hydrogen gas (\(E^\circ = -0.83\) V). Similarly, the standard electrode potential for the oxidation of water to oxygen gas (\(E^\circ = +1.23\) V) is more favorable compared to the oxidation of copper metal (\(E^\circ = +0.34\) V).

Platinum Electrodes: Platinum is an inert electrode that does not participate in the chemical reactions but provides a surface for the reactions to occur.

Given the above explanations, the correct answers are:

A. Copper will deposit at the cathode: True. Copper is reduced and deposited on the cathode.

C. Oxygen will be released at the anode: True. Water is oxidized to produce oxygen gas at the anode.

Therefore, the correct answer is 2. A and C only.