0.5 M HCI solution has ions `Hg^(+), Cd^(2), Sr^(+2), Fe^(+2), Cu^(+2)`. If `H_(2)S` gas in passed through this solution, the ions which are precipitated out are

Options

A. `Cd^(+2), Fe^(+2), Sr^(+2)`
B. `Cd^(+2), Hg^(+2), Cu^(+2)`
C. `Hg^(+2), Cu^(+2), Fe^(+2)`
D. `Cu^(+2), Sr^(+2), Fe^(+2)`

Answer

To solve the problem, we need to determine which ions will precipitate when H₂S gas is passed through a 0.5 M HCl solution containing the ions Hg²⁺, Cd²⁺, Sr²⁺, Fe²⁺, and Cu²⁺.

### Step-by-Step Solution:

1. **Identify the ions present in the solution**:
The solution contains the following ions:
- Hg²⁺ (Mercury)
- Cd²⁺ (Cadmium)
- Sr²⁺ (Strontium)
- Fe²⁺ (Iron)
- Cu²⁺ (Copper)

2. **Understand the effect of H₂S**:
When H₂S gas is passed through the solution, it dissociates into H⁺ and HS⁻ ions. The HS⁻ ions can react with certain metal cations to form insoluble sulfides.

3. **Determine the solubility of sulfides**:
The sulfides of certain metals are insoluble in water. The relevant sulfides for the ions present are:
- HgS (Mercury sulfide) - insoluble
- CdS (Cadmium sulfide) - insoluble
- SrS (Strontium sulfide) - soluble
- FeS (Iron sulfide) - insoluble
- CuS (Copper sulfide) - insoluble

4. **Identify which ions will precipitate**:
Based on the solubility of the sulfides:
- Hg²⁺ will precipitate as HgS.
- Cd²⁺ will precipitate as CdS.
- Sr²⁺ will not precipitate as SrS is soluble.
- Fe²⁺ will precipitate as FeS.
- Cu²⁺ will precipitate as CuS.

5. **List the precipitated ions**:
The ions that will precipitate when H₂S is passed through the solution are:
- Hg²⁺ (as HgS)
- Cd²⁺ (as CdS)
- Fe²⁺ (as FeS)
- Cu²⁺ (as CuS)

### Final Answer:
The ions that will precipitate out are Hg²⁺, Cd²⁺, Fe²⁺, and Cu²⁺.