The solubility product of a sulphide MS is ` 3 xx 10 ^(-25) ` and that of another sulphide NS is ` 4 xx 10 ^(-40)` In ammonical solution

Options

A. only NS gets precipitated
B. only MS gets precipitated
C. neither sulphide precipitates out
D. both sulphides precipitate out.

Answer

To solve the problem regarding the solubility of the sulfides MS and NS in an ammonical solution, we need to analyze the given solubility products and the conditions under which these sulfides can precipitate.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- The solubility product (Ksp) of sulfide MS is \( K_{sp}(MS) = 3 \times 10^{-25} \).
- The solubility product (Ksp) of sulfide NS is \( K_{sp}(NS) = 4 \times 10^{-40} \).

2. **Understanding Ammonical Solution:**
- In an ammonical solution, the presence of NH4Cl suppresses the ionization of H2S due to the common ion effect. This results in a lower concentration of sulfide ions (S²⁻) in the solution.

3. **Determine the Conditions for Precipitation:**
- A sulfide will precipitate when the ionic product (IP) of the sulfide exceeds its solubility product (Ksp).
- In ammonical solution, the concentration of S²⁻ is reduced, which means that the ionic product for both sulfides may be less than their respective Ksp values.

4. **Evaluate the Precipitation of Each Sulfide:**
- For sulfide MS:
- Since \( K_{sp}(MS) = 3 \times 10^{-25} \) is significantly larger than \( K_{sp}(NS) = 4 \times 10^{-40} \), MS is more soluble than NS.
- For sulfide NS:
- Given that \( K_{sp}(NS) \) is much smaller, NS is less soluble and will precipitate more readily when the concentration of S²⁻ is low.

5. **Conclusion on Precipitation:**
- In ammonical solution, the concentration of S²⁻ is lowered, which means that both sulfides may not exceed their Ksp values.
- However, since NS has a much lower Ksp, it is more likely to precipitate out first.
- The common ion effect in the ammonical solution means that neither sulfide may precipitate if the ionic product remains below their Ksp values.

6. **Final Answer:**
- Therefore, the correct option is that **neither sulfide precipitates out** in the ammonical solution.