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_4Cl` 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 0.1 M solutions of the compounds, we need to analyze the nature of each compound and its effect on pH.

1. **Identify the compounds and their nature:**
- (A) `HCOONH4` (Ammonium formate): This is a salt formed from formic acid (a weak acid) and ammonium hydroxide (a weak base).
- (B) `CH3COONH4` (Ammonium acetate): This is a salt formed from acetic acid (a weak acid) and ammonium hydroxide (a weak base).
- (C) `CH3COONa` (Sodium acetate): This is a salt formed from acetic acid (a weak acid) and sodium hydroxide (a strong base).
- (D) `NH4Cl` (Ammonium chloride): This is a salt formed from hydrochloric acid (a strong acid) and ammonium hydroxide (a weak base).

2. **Determine the acidity or basicity of each compound:**
- (A) `HCOONH4`: Since it is a salt of a weak acid and a weak base, it will have a pH that is slightly acidic.
- (B) `CH3COONH4`: Similar to (A), it is a salt of a weak acid and a weak base, but the pH will be slightly higher than that of ammonium formate due to the weaker acidity of acetic acid compared to formic acid.
- (C) `CH3COONa`: This salt is formed from a weak acid and a strong base, resulting in a basic solution. Therefore, it will have a higher pH.
- (D) `NH4Cl`: This salt is formed from a strong acid and a weak base, making it acidic in nature. Thus, it will have the lowest pH.

3. **Comparing the pH values:**
- Since `NH4Cl` is acidic, it will have the lowest pH.
- Next, `HCOONH4` will have a slightly higher pH than `NH4Cl`.
- Then, `CH3COONH4` will have a higher pH than `HCOONH4`.
- Finally, `CH3COONa` will have the highest pH due to its basic nature.

4. **Conclusion:**
The increasing order of pH for the compounds is:
\[ NH4Cl < HCOONH4 < CH3COONH4 < CH3COONa \]

Thus, the correct increasing order of pH is:
**(D) NH4Cl < (A) HCOONH4 < (B) CH3COONH4 < (C) CH3COONa**