A solution contain `0.1 MZn^(2+)` and `0.01 M Cu^(+2)` ins. This solution is saturated by passing `H_(2)S` concentration is `8.1' 10^(-21) M` . Ksp for `ZnS` and `CuS` are `3'10^(-22)` and` 8'10^(-36)` respectively. Which of the following will occur in solution.

Options

A. ZnS will precipitate
B. CuS will precipipate
C. Both ZnS and CuS will precipate
D. Both `Zn^(2+)` and `Cu^(2+)` will remains in the solution

Answer

To solve the problem, we need to determine whether ZnS or CuS will precipitate when H2S is passed through a solution containing Zn²⁺ and Cu²⁺ ions. We will calculate the ionic products for both salts and compare them with their respective solubility products (Ksp).

### Step-by-Step Solution:

1. **Identify the given concentrations**:
- Concentration of Zn²⁺ = 0.1 M
- Concentration of Cu²⁺ = 0.01 M
- Concentration of S²⁻ from H2S = 8.1 × 10^(-21) M

2. **Calculate the ionic product (IP) for ZnS**:
- The ionic product for ZnS is given by:
\[ IP_{ZnS} = [Zn^{2+}][S^{2-}] \]
- Substituting the values:
\[ IP_{ZnS} = (0.1)(8.1 \times 10^{-21}) = 8.1 \times 10^{-22} \]

3. **Calculate the ionic product (IP) for CuS**:
- The ionic product for CuS is given by:
\[ IP_{CuS} = [Cu^{2+}][S^{2-}] \]
- Substituting the values:
\[ IP_{CuS} = (0.01)(8.1 \times 10^{-21}) = 8.1 \times 10^{-23} \]

4. **Compare the ionic products with the solubility products (Ksp)**:
- Given Ksp for ZnS = 3 × 10^(-22)
- Given Ksp for CuS = 8 × 10^(-36)

5. **Determine precipitation for ZnS**:
- Since \( IP_{ZnS} = 8.1 \times 10^{-22} \) and \( Ksp_{ZnS} = 3 \times 10^{-22} \):
\[ IP_{ZnS} > Ksp_{ZnS} \]
- This indicates that ZnS will precipitate.

6. **Determine precipitation for CuS**:
- Since \( IP_{CuS} = 8.1 \times 10^{-23} \) and \( Ksp_{CuS} = 8 \times 10^{-36} \):
\[ IP_{CuS} > Ksp_{CuS} \]
- This indicates that CuS will also precipitate.

7. **Conclusion**:
- Both ZnS and CuS will precipitate from the solution. However, since the ionic product for CuS is significantly lower than its Ksp, CuS will precipitate more readily than ZnS.

### Final Answer:
Both ZnS and CuS will precipitate, but CuS will precipitate first due to its much lower Ksp compared to its ionic product.