Physics 2001 JAMB Past Questions - Question 29: In a Daniell cell, the depolarizer, positive and negative electrodes are respectively

Correct Answer

A

Explanation

In a Daniell cell, which is an early type of electrochemical cell used to generate electricity, the depolarizer, positive electrode, and negative electrode are as follows:

1. Depolarizer: The depolarizer in a Daniell cell is typically composed of a solution of copper sulfate (CuSO4). This solution is responsible for preventing the buildup of hydrogen gas at the negative electrode (cathode) and ensuring a more stable and long-lasting electrochemical reaction.

2. Positive Electrode (Anode): The positive electrode or anode in a Daniell cell is made of a copper metal rod or plate. This copper electrode is immersed in the copper sulfate solution. During the cell's operation, oxidation occurs at the anode, where copper metal is oxidized to release copper ions (Cu²⁺) into the solution. The half-reaction at the anode is:

Cu(s) → Cu²⁺(aq) + 2e⁻

3. Negative Electrode (Cathode): The negative electrode or cathode in a Daniell cell is made of a zinc metal rod or plate. This zinc electrode is immersed in a solution of zinc sulfate (ZnSO4). Reduction occurs at the cathode, where zinc ions (Zn²⁺) in the solution gain electrons to form solid zinc metal. The half-reaction at the cathode is:

Zn²⁺(aq) + 2e⁻ → Zn(s)

The overall cell reaction in a Daniell cell involves the transfer of electrons from the anode to the cathode, with copper being deposited on the cathode and zinc being oxidized at the anode. This electrochemical process generates electrical energy.