The metal ions which are precipitated when `H_(2)S` gas is passed in the presence of dilute HCl is :

Options

A. `Zn^(2+)`
B. `Ni^(2+)`
C. `Cd^(2+)`
D. `Mn^(2+)`

Explanation

To solve the question regarding the metal ions that are precipitated when H₂S gas is passed in the presence of dilute HCl, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When H₂S (hydrogen sulfide) is introduced into a solution, it can react with certain metal ions to form metal sulfide precipitates. The presence of dilute HCl creates an acidic environment.

2. **Identifying the Metal Ions**:
- In acidic conditions, only certain metal ions will precipitate with H₂S. The metal ions that typically precipitate in acidic solutions include cadmium (Cd²⁺), lead (Pb²⁺), and mercury (Hg²⁺).

3. **Formation of Precipitates**:
- When H₂S gas is bubbled through the solution, cadmium ions react with H₂S to form cadmium sulfide (CdS), which is a yellow precipitate.
- The reaction can be represented as:
\[ \text{Cd}^{2+} + \text{H}_2\text{S} \rightarrow \text{CdS (s)} + 2\text{H}^+ \]

4. **Exclusion of Other Metal Ions**:
- Other metal ions like zinc (Zn²⁺), nickel (Ni²⁺), and manganese (Mn²⁺) are part of group four elements and typically do not precipitate in acidic conditions. They require an alkaline medium to form precipitates with H₂S.

5. **Conclusion**:
- The metal ion that precipitates when H₂S is passed in the presence of dilute HCl is cadmium (Cd²⁺), forming cadmium sulfide (CdS).

### Final Answer:
The metal ion which is precipitated when H₂S gas is passed in the presence of dilute HCl is **Cadmium (Cd²⁺)**.