Which of the following increasing order of pH of 0.1 M solution of the compound
(A) `HCOONH_4`
(B) `CH_3COONH_4`
( C ) `CH_3COONa`
(D) `NH_4CI` is correct ?

Options

A. `A lt D lt B lt C`
B. `D lt A lt C lt B`
C. `A lt D lt C lt B`
D. `D lt A lt B lt C`

Answer

To determine the increasing order of pH for the given compounds in a 0.1 M solution, we need to analyze the nature of each compound in terms of their acidic and basic properties.

### Step 1: Identify the nature of each compound

1. **HCOONH₄ (Ammonium formate)**: This is a salt formed from a weak acid (formic acid) and a weak base (ammonia). It will produce a weakly acidic solution.

2. **CH₃COONH₄ (Ammonium acetate)**: This is a salt formed from a weak acid (acetic acid) and a weak base (ammonia). Similar to ammonium formate, it will also produce a weakly acidic solution.

3. **CH₃COONa (Sodium acetate)**: This is a salt formed from a weak acid (acetic acid) and a strong base (sodium hydroxide). It will produce a basic solution.

4. **NH₄Cl (Ammonium chloride)**: This is a salt formed from a strong acid (hydrochloric acid) and a weak base (ammonia). It will produce an acidic solution.

### Step 2: Determine the pH of each solution

- **HCOONH₄**: Weak acid + weak base → weakly acidic solution (pH < 7)

- **CH₃COONH₄**: Weak acid + weak base → weakly acidic solution (pH < 7, but higher than HCOONH₄ due to the stability of the acetate ion)

- **CH₃COONa**: Weak acid + strong base → basic solution (pH > 7)

- **NH₄Cl**: Strong acid + weak base → acidic solution (pH < 7, lower than both HCOONH₄ and CH₃COONH₄)

### Step 3: Compare the pH values

From the analysis:
- NH₄Cl has the lowest pH (most acidic).
- HCOONH₄ is next (weakly acidic).
- CH₃COONH₄ is slightly higher than HCOONH₄ (still weakly acidic).
- CH₃COONa has the highest pH (basic).

### Final Order of Increasing pH

Thus, the increasing order of pH for the 0.1 M solutions of the compounds is:
**NH₄Cl < HCOONH₄ < CH₃COONH₄ < CH₃COONa**

### Answer:
The correct increasing order of pH is:
**(D) NH₄Cl < (A) HCOONH₄ < (B) CH₃COONH₄ < (C) CH₃COONa**

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