In a solution containing `Cu^(2+)` and `Cd^(2+)` dil. `H_(2)SO_(4)` is added followed by iron filings. The solution is warmed and `NH_(4)OH` is added to reduce the acidity followed by passing of `H_(2)S` gas. The ppt. obtained will be

Options

A. CuS only
B. CdS only
C. Both Cu metal and CdS
D. CuS, CdS and `FeSO_(4)`

Explanation

To solve the given problem step by step, we will analyze the reactions that occur when `Cu^(2+)` and `Cd^(2+)` ions are treated with dilute `H2SO4`, followed by iron filings, `NH4OH`, and `H2S` gas.

### Step-by-Step Solution:

1. **Identify the Initial Components:**
- The solution contains `Cu^(2+)` (Copper ions) and `Cd^(2+)` (Cadmium ions).
- Dilute `H2SO4` is added to the solution.

2. **Dissociation of Dilute H2SO4:**
- The dilute sulfuric acid dissociates into `H^+` ions and `SO4^(2-)` ions:
\[ H2SO4 \rightarrow 2H^+ + SO4^{2-} \]

3. **Addition of Iron Filings:**
- Iron filings are added to the solution. Iron acts as a reducing agent and gets oxidized:
\[ Fe \rightarrow Fe^{2+} + 2e^- \]

4. **Reduction of Copper and Cadmium Ions:**
- The `Cu^(2+)` and `Cd^(2+)` ions in the solution will accept electrons from the oxidized iron. Since `Cu^(2+)` is a stronger oxidizing agent than `Cd^(2+)`, it will be reduced first:
\[ Cu^{2+} + 2e^- \rightarrow Cu \quad (\text{precipitate of copper}) \]
- `Cd^(2+)` ions will remain in the solution at this stage.

5. **Addition of NH4OH:**
- `NH4OH` (ammonium hydroxide) is added to reduce the acidity of the solution. This does not affect the precipitate formed from copper but helps in preparing the solution for the next step.

6. **Passing H2S Gas:**
- When `H2S` gas is passed into the solution, it dissociates into `H^+` and `S^{2-}` ions:
\[ H2S \rightarrow 2H^+ + S^{2-} \]
- The `S^{2-}` ions react with the remaining `Cd^(2+)` ions in the solution to form cadmium sulfide (CdS) precipitate:
\[ Cd^{2+} + S^{2-} \rightarrow CdS \quad (\text{precipitate of cadmium sulfide}) \]

7. **Final Result:**
- The final precipitates formed in the solution are:
- Copper metal (Cu)
- Cadmium sulfide (CdS)

### Conclusion:
The precipitate obtained will be both copper metal (Cu) and cadmium sulfide (CdS).