The pH of 0.1 M solution of the following salts increases in the order.

Options

A. ` NaCl lt NH_4Cl gt NaCN gt HCl`
B. ` HCl lt NH_4Cl lt NaCl lt NaCN`
C. ` NaCN lt NH_4Cl lt NaCl lt HCl`
D. ` HCl lt NaCl lt NaCN lt NH_4Cl.`

Answer

To determine the order of pH for a 0.1 M solution of the given salts, we need to analyze each salt based on the strength of the acids and bases from which they are derived. Here’s a step-by-step solution:

### Step 1: Analyze NaCl
- **Formation**: NaCl is formed from the strong acid HCl and the strong base NaOH.
- **pH**: Since both the acid and base are strong, NaCl is a neutral salt. Therefore, the pH of a 0.1 M NaCl solution is approximately 7.

### Step 2: Analyze NH4Cl
- **Formation**: NH4Cl is formed from the strong acid HCl and the weak base NH4OH (ammonium hydroxide).
- **pH**: Since NH4Cl is derived from a strong acid and a weak base, it is an acidic salt. Therefore, the pH of a 0.1 M NH4Cl solution will be less than 7.

### Step 3: Analyze NaCN
- **Formation**: NaCN is formed from the weak acid HCN and the strong base NaOH.
- **pH**: Since NaCN is derived from a weak acid and a strong base, it is a basic salt. Therefore, the pH of a 0.1 M NaCN solution will be greater than 7.

### Step 4: Analyze HCl
- **Formation**: HCl is a strong acid.
- **pH**: The pH of a strong acid like HCl in a 0.1 M solution is significantly low, typically around 1 or 2. Therefore, the pH of HCl is much less than 7.

### Conclusion
Now, we can summarize the pH values:
- **HCl**: pH < 3 (very acidic)
- **NH4Cl**: pH < 7 (acidic)
- **NaCl**: pH = 7 (neutral)
- **NaCN**: pH > 7 (basic)

### Order of pH from lowest to highest:
1. HCl (pH < 3)
2. NH4Cl (pH < 7)
3. NaCl (pH = 7)
4. NaCN (pH > 7)

Thus, the increasing order of pH for the 0.1 M solutions of the salts is:
**HCl < NH4Cl < NaCl < NaCN**