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

Options

A. `NaCl lt NH_(4)Cl lt NaCH 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 order of pH for the given salts in a 0.1 M solution, we need to analyze the nature of each salt and how they affect the pH of the solution. Let's break down the salts provided:

1. **HCl**: This is a strong acid. When dissolved in water, it completely dissociates into H⁺ and Cl⁻ ions. The pH of a strong acid solution is less than 7. Therefore, the pH of a 0.1 M HCl solution will be approximately 1.

2. **NaCl**: This salt is formed from a strong acid (HCl) and a strong base (NaOH). In solution, NaCl dissociates into Na⁺ and Cl⁻ ions, neither of which hydrolyze to affect the pH significantly. Thus, the solution remains neutral with a pH close to 7.

3. **NH4Cl**: This salt is formed from a weak base (NH₃) and a strong acid (HCl). In solution, NH4Cl dissociates into NH4⁺ and Cl⁻ ions. The NH4⁺ ion can donate a proton (H⁺) to water, making the solution acidic. Therefore, the pH will be less than 7.

4. **NaCN**: This salt is formed from a strong base (NaOH) and a weak acid (HCN). In solution, NaCN dissociates into Na⁺ and CN⁻ ions. The CN⁻ ion can accept a proton from water, making the solution basic. Therefore, the pH will be greater than 7.

Now, we can summarize the pH levels for each salt:
- **HCl**: pH < 7 (acidic)
- **NH4Cl**: pH < 7 (acidic)
- **NaCl**: pH ≈ 7 (neutral)
- **NaCN**: pH > 7 (basic)

Now, we can arrange the salts in order of increasing pH:
1. HCl (lowest pH)
2. NH4Cl
3. NaCl
4. NaCN (highest pH)

Thus, the order of pH of the salts in a 0.1 M solution increases as follows:
**HCl < NH4Cl < NaCl < NaCN**