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 determine which ions precipitate when H₂S gas is passed through a 0.5 M HCl solution containing the ions Hg⁺, Cd²⁺, Sr²⁺, Fe²⁺, and Cu²⁺, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the ions present in the solution**:
The ions present in the 0.5 M HCl solution are:
- Hg⁺ (mercury(I))
- Cd²⁺ (cadmium)
- Sr²⁺ (strontium)
- Fe²⁺ (iron)
- Cu²⁺ (copper)

2. **Understand the effect of H₂S in acidic medium**:
When H₂S gas is passed through an acidic solution (like HCl), it can precipitate certain metal sulfides. The solubility of metal sulfides varies depending on the metal ion.

3. **Check the solubility of sulfides**:
- **HgS** (mercury sulfide) is insoluble and will precipitate.
- **CdS** (cadmium sulfide) is also insoluble and will precipitate.
- **SrS** (strontium sulfide) is soluble in acidic solutions and will not precipitate.
- **FeS** (iron sulfide) is insoluble and will precipitate.
- **CuS** (copper sulfide) is insoluble and will precipitate.

4. **List the precipitated ions**:
Based on the above solubility rules, the ions that will precipitate out when H₂S is passed through the solution are:
- HgS (from Hg⁺)
- CdS (from Cd²⁺)
- FeS (from Fe²⁺)
- CuS (from Cu²⁺)

5. **Final conclusion**:
The ions that precipitate out of the solution when H₂S gas is passed through it are:
- Cd²⁺
- Fe²⁺
- Cu²⁺

### Summary of Precipitated Ions:
- **Cadmium (Cd²⁺)**
- **Iron (Fe²⁺)**
- **Copper (Cu²⁺)**