White precipitate of silver chloride is soluble in:

Options

A. `KCN` solution (excess)
B. sodium thiosulphate solution (excess)
C. ammonia solution
D. concentrated solution of `KCl`

Explanation

To determine the solubility of the white precipitate of silver chloride (AgCl), we need to analyze its behavior in different solutions. Here’s a step-by-step breakdown:

### Step 1: Understanding the Precipitate
AgCl is a white precipitate that is generally insoluble in water. However, it can dissolve in certain solutions due to the formation of soluble complexes.

### Step 2: Solubility in KCN (Potassium Cyanide) Solution
When AgCl is added to an excess of KCN solution, the cyanide ions (CN⁻) react with silver ions (Ag⁺) to form a soluble complex:
\[ \text{AgCl} + 2 \text{CN}^- \rightarrow [\text{Ag(CN)}_2]^- + \text{Cl}^- \]
This complex, \([\text{Ag(CN)}_2]^-\), is soluble, indicating that AgCl is soluble in KCN solution.

**Hint:** Look for active ions in the solution that can form complexes with Ag⁺ ions.

### Step 3: Solubility in Sodium Thiosulfate Solution
When AgCl is treated with sodium thiosulfate (Na2S2O3), the thiosulfate ions (S2O3²⁻) react with Ag⁺ ions to form another soluble complex:
\[ \text{AgCl} + 2 \text{S}_2\text{O}_3^{2-} \rightarrow [\text{Ag(S}_2\text{O}_3)_2]^{3-} + \text{Cl}^- \]
The complex \([\text{Ag(S}_2\text{O}_3)_2]^{3-}\) is also soluble, confirming that AgCl is soluble in sodium thiosulfate solution.

**Hint:** Identify the ions that can stabilize the silver ion in solution.

### Step 4: Solubility in Ammonia Solution
When AgCl is added to ammonia (NH3) solution, it forms a soluble complex:
\[ \text{AgCl} + 2 \text{NH}_3 \rightarrow [\text{Ag(NH}_3)_2]^+ + \text{Cl}^- \]
The complex \([\text{Ag(NH}_3)_2]^+\) is soluble, indicating that AgCl is soluble in ammonia solution.

**Hint:** Consider how ligands like ammonia can coordinate with metal ions to increase solubility.

### Step 5: Solubility in Concentrated KCl Solution
In concentrated KCl solution, AgCl can also dissolve due to the formation of the complex:
\[ \text{AgCl} + \text{Cl}^- \rightarrow [\text{AgCl}_2]^- \]
This complex, \([\text{AgCl}_2]^-\), is soluble, showing that AgCl is soluble in concentrated KCl solution.

**Hint:** Look for the effect of high concentrations of chloride ions on the solubility of silver chloride.

### Conclusion
AgCl is soluble in all the mentioned solutions: KCN, sodium thiosulfate, ammonia, and concentrated KCl. Each of these solutions facilitates the formation of soluble complexes with silver ions.