To have more sulphide ion concentraion `H_(2)S` should be passed through

Options

A. 1 N HCI solution
B. 0.1 H HCI solution
C. A neutral solution such as water
D. An ammonical solution

Answer

To determine how to increase the concentration of sulfide ions (S²⁻) by passing hydrogen sulfide (H₂S) through different solutions, we need to understand the concepts of the common ion effect and the odd ion effect. Here’s a step-by-step solution:

### Step 1: Understanding the Dissociation of H₂S
H₂S is a weak acid that dissociates in water to produce hydrogen ions (H⁺) and sulfide ions (S²⁻):
\[ \text{H}_2\text{S} \rightleftharpoons \text{H}^+ + \text{HS}^- \]
\[ \text{HS}^- \rightleftharpoons \text{H}^+ + \text{S}^{2-} \]

### Step 2: Effect of Strong Acid (HCl)
When H₂S is passed through a strong acid like HCl, the concentration of H⁺ ions increases significantly. This leads to the common ion effect, where the presence of a common ion (H⁺) suppresses the dissociation of H₂S:
- Increased H⁺ concentration shifts the equilibrium to the left, resulting in fewer sulfide ions (S²⁻).

### Step 3: Effect of Weak Acid (0.1 N HCl)
In a 0.1 N HCl solution, the effect is similar to that of a strong acid, but less pronounced due to the lower concentration of H⁺ ions compared to 1 N HCl. However, it still results in a decrease in the concentration of S²⁻ due to the common ion effect.

### Step 4: Effect of Neutral Solution
In a neutral solution, there are no additional H⁺ ions introduced. The dissociation of H₂S remains unaffected, and the concentration of sulfide ions will be at a moderate level, but not increased.

### Step 5: Effect of Ammonical Solution
When H₂S is passed through an ammonical (basic) solution, the presence of OH⁻ ions will neutralize H⁺ ions:
\[ \text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O} \]
- This reduction in H⁺ concentration shifts the equilibrium of H₂S dissociation to the right, resulting in an increase in the concentration of sulfide ions (S²⁻).

### Conclusion
To achieve a higher concentration of sulfide ions (S²⁻), H₂S should be passed through an ammonical solution. This is because the basic environment reduces the concentration of H⁺ ions, allowing more H₂S to dissociate and produce sulfide ions.

### Final Answer
**The correct option is: Ammonical solution (Option 4)**