Write cell reaction of the following cells :
`Pt,H_2|H^+(aq)||Cd^(2+)(aq)|Cd`

Answer

To write the cell reaction for the given electrochemical cell represented as `Pt, H2 | H+(aq) || Cd^(2+)(aq) | Cd`, we can break it down into two half-reactions: oxidation and reduction.

### Step-by-Step Solution:

1. **Identify the Anode and Cathode:**
- In this cell representation, the anode is on the left side (where oxidation occurs) and the cathode is on the right side (where reduction occurs).
- Anode: Platinum electrode with H2 gas.
- Cathode: Cadmium electrode with Cd²⁺ ions in solution.

2. **Write the Oxidation Half-Reaction (Anode):**
- At the anode, hydrogen gas (H2) is oxidized to hydrogen ions (H⁺).
- The oxidation reaction can be written as:
\[ \text{H}_2(g) \rightarrow 2\text{H}^+(aq) + 2e^- \]
- Here, 2 electrons are released during the oxidation of H2.

3. **Write the Reduction Half-Reaction (Cathode):**
- At the cathode, cadmium ions (Cd²⁺) are reduced to solid cadmium (Cd).
- The reduction reaction can be written as:
\[ \text{Cd}^{2+}(aq) + 2e^- \rightarrow \text{Cd}(s) \]
- Here, 2 electrons are consumed during the reduction of Cd²⁺.

4. **Combine the Half-Reactions:**
- Now, we can combine the oxidation and reduction half-reactions to write the overall cell reaction.
- The electrons cancel out, leading to the overall reaction:
\[ \text{H}_2(g) + \text{Cd}^{2+}(aq) \rightarrow 2\text{H}^+(aq) + \text{Cd}(s) \]

### Final Cell Reaction:
\[ \text{H}_2(g) + \text{Cd}^{2+}(aq) \rightarrow 2\text{H}^+(aq) + \text{Cd}(s) \]