Which of the following reagents can be used for making the distinction between `AgCl` and `AgI`?

Options

A. Sodium arsenite solution
B. Dilute ammonia solution
C. Potassium cyanide solution
D. Dilute `HNO_(3)`

Explanation

To distinguish between AgCl (silver chloride) and AgI (silver iodide), we can analyze the behavior of these compounds when treated with different reagents. Here’s a step-by-step solution:

### Step 1: Understand the Solubility of AgCl and AgI
- AgCl is soluble in dilute ammonia, forming a soluble complex [Ag(NH3)2]+.
- AgI is insoluble in dilute ammonia and does not form a complex.

### Step 2: Evaluate the Reagents
1. **Sodium Arsenate Solution (Na2As2O3)**:
- Both AgCl and AgI form soluble complexes with sodium arsenate.
- Therefore, this reagent cannot distinguish between AgCl and AgI.

2. **Dilute Ammonia**:
- AgCl reacts with dilute ammonia to form a soluble complex: [Ag(NH3)2]+.
- AgI does not react and remains insoluble.
- This reagent can effectively distinguish between AgCl and AgI.

3. **Potassium Cyanide Solution (KCN)**:
- Both AgCl and AgI are soluble in potassium cyanide.
- Hence, this reagent cannot be used for distinction.

4. **Dilute HNO3**:
- Both AgCl and AgI are soluble in dilute nitric acid.
- Thus, this reagent also cannot distinguish between the two.

### Conclusion
The reagent that can be used to distinguish between AgCl and AgI is **dilute ammonia**.