The oxidation state of copper changes when aqueous copper (II) ions react with:
(I)`NaOH(aq)` (II)`Fe(s)` (III)`KI(aq)`

Options

A. I, II, III
B. II only
C. II, III
D. I only

Answer

To determine the changes in the oxidation state of copper when it reacts with different reagents, we will analyze each reaction step by step.

### Step 1: Reaction with Aqueous NaOH
1. **Write the reaction**: When copper(II) ions react with sodium hydroxide (NaOH), the reaction can be represented as:
\[ \text{Cu}^{2+} + 2 \text{OH}^- \rightarrow \text{Cu(OH)}_2 \]
Here, copper(II) ions (Cu²⁺) react with hydroxide ions (OH⁻) to form copper(II) hydroxide (Cu(OH)₂).

2. **Determine oxidation states**: In this reaction:
- The oxidation state of copper in Cu²⁺ is +2.
- In Cu(OH)₂, copper remains in the +2 oxidation state.

3. **Conclusion**: There is **no change** in the oxidation state of copper when it reacts with NaOH.

### Step 2: Reaction with Solid Iron
1. **Write the reaction**: When copper(II) ions react with iron (Fe), the reaction can be represented as:
\[ \text{Cu}^{2+} + \text{Fe} \rightarrow \text{Cu}^0 + \text{Fe}^{2+} \]
Here, solid iron displaces copper from its salt.

2. **Determine oxidation states**: In this reaction:
- The oxidation state of copper changes from +2 (Cu²⁺) to 0 (Cu).
- Iron (Fe) is oxidized from 0 to +2 (Fe²⁺).

3. **Conclusion**: The oxidation state of copper **changes** from +2 to 0 when it reacts with iron.

### Step 3: Reaction with Aqueous KI
1. **Write the reaction**: When copper(II) ions react with potassium iodide (KI), the reaction can be represented as:
\[ 2 \text{Cu}^{2+} + 4 \text{KI} \rightarrow \text{Cu}_2\text{I}_2 + 2 \text{I}_2 + 4 \text{K}^+ \]
Here, copper(II) ions react with iodide ions to form copper(I) iodide (CuI) and iodine (I₂).

2. **Determine oxidation states**: In this reaction:
- The oxidation state of copper changes from +2 (Cu²⁺) to +1 (Cu⁺) in CuI.
- The iodine (I) is reduced from -1 in KI to 0 in I₂.

3. **Conclusion**: The oxidation state of copper **changes** from +2 to +1 when it reacts with KI.

### Final Summary
- **NaOH**: No change in oxidation state (Cu remains +2).
- **Fe**: Change in oxidation state from +2 to 0.
- **KI**: Change in oxidation state from +2 to +1.

### Answer
The oxidation state of copper changes when it reacts with **(II) Fe(s)** and **(III) KI(aq)**. Therefore, the correct answer is **(II) and (III)**.