The reaction which is taking place in nickel cadmium battery can be represented by which of the following equations?

Options

A. `Cd+NiO_2 + 2H_2O to Cd(OH)_2 + Ni(OH)_2`
B. `Cd+ NiO_2 + 2OH^(-) to Ni + Cd(OH)_2`
C. `Ni+ Cd(OH)_2 to Cd to Ni(OH)_2`
D. `Ni(OH)_2 + Cd(OH)_2 to Ni + Cd + 2H_2O`

Explanation

To determine the reaction taking place in a nickel-cadmium battery, we can break it down into the anode and cathode reactions and then combine them to find the overall reaction.

### Step-by-Step Solution:

1. **Identify the Anode Reaction:**
- In a nickel-cadmium battery, the anode reaction involves cadmium (Cd) and hydroxide ions (OH⁻).
- The anode reaction can be written as:
\[ \text{Cd (s)} + 2 \text{OH}^- \rightarrow \text{Cd(OH)}_2 (s) + 2 \text{e}^- \]

2. **Identify the Cathode Reaction:**
- The cathode reaction involves nickel oxide or nickel peroxide (NiO or NiO₂) and water (H₂O).
- The cathode reaction can be written as:
\[ \text{NiO}_2 (s) + 2 \text{H}_2\text{O} + 2 \text{e}^- \rightarrow \text{Ni(OH)}_2 (s) + 2 \text{OH}^- \]

3. **Combine the Anode and Cathode Reactions:**
- To find the overall reaction, we add the anode and cathode reactions together.
- The electrons cancel out, leading to the overall reaction:
\[ \text{Cd (s)} + \text{NiO}_2 (s) + 2 \text{H}_2\text{O} (l) \rightarrow \text{Cd(OH)}_2 (s) + \text{Ni(OH)}_2 (s) \]

4. **Identify the Correct Option:**
- From the overall reaction derived, we can see that the correct representation of the reaction taking place in a nickel-cadmium battery is:
\[ \text{Cd (s)} + \text{NiO}_2 (s) + 2 \text{H}_2\text{O} (l) \rightarrow \text{Cd(OH)}_2 (s) + \text{Ni(OH)}_2 (s) \]
- Therefore, the correct option is option A, which states:
\[ \text{Cd} + \text{NiO}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Cd(OH)}_2 + \text{Ni(OH)}_2 \]