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

Options

A. `NaCl lt NH_(4)Cl lt NaCN lt HCl`
B. `HCl lt NH_(4)Cl lt NaCl lt NaCN`
C. `NaCN lt NH_(4)Cl lt NaCl lt HCl`
D. `HCl lt NaCl lt NaCN lt NH_(4)Cl`

Answer

To determine the increasing order of pH for a 0.1 M solution of the given salts (NaCl, HCl, NH4Cl, and NaCN), we need to analyze the nature of each salt and how they affect the pH of the solution.

### Step-by-Step Solution:

1. **Identify the Nature of Each Salt:**
- **NaCl:** This salt is formed from a strong acid (HCl) and a strong base (NaOH). Therefore, it is neutral and will have a pH of 7.
- **HCl:** This is a strong acid. A 0.1 M solution of HCl will have a pH less than 7. Specifically, since it completely dissociates, the pH can be calculated as:
\[ \text{pH} = -\log[H^+] = -\log[0.1] = 1 \]
- **NH4Cl:** This salt is formed from a weak base (NH4OH) and a strong acid (HCl). The pH will be less than 7 but greater than that of HCl because NH4Cl will produce NH4+ ions, which can slightly increase the acidity. The pH will typically be around 5-6.
- **NaCN:** This salt is formed from a strong base (NaOH) and a weak acid (HCN). The pH will be greater than 7 because NaCN will produce CN- ions, which will make the solution basic. The pH can be calculated to be around 10-11.

2. **Compare the pH Values:**
- HCl: pH ≈ 1 (lowest)
- NH4Cl: pH ≈ 5-6
- NaCl: pH = 7 (neutral)
- NaCN: pH ≈ 10-11 (highest)

3. **Determine the Increasing Order of pH:**
- From the above analysis, we can arrange the salts in order of increasing pH:
- HCl < NH4Cl < NaCl < NaCN

### Final Answer:
The increasing order of pH for the 0.1 M solutions of the given salts is:
**HCl < NH4Cl < NaCl < NaCN**