Identify correct order of pH of the given solutions at `25^(@)C`
(I) `NH_(4)Cl " "` (II) `Na_(2)CO_(3) " "` (III) `K_(2)SO_(4)`

Options

A. `I lt II lt III`
B. `I lt III lt II`
C. `II lt I lt III`
D. `II lt III lt I`

Explanation

To determine the correct order of pH for the given solutions at 25°C, we need to analyze the nature of each salt and its effect on the pH of the solution.

### Step-by-Step Solution:

1. **Identify the salts and their components:**
- (I) Ammonium Chloride (NH₄Cl)
- (II) Sodium Carbonate (Na₂CO₃)
- (III) Potassium Sulphate (K₂SO₄)

2. **Analyze Ammonium Chloride (NH₄Cl):**
- Ammonium chloride is formed from a weak base (NH₄OH) and a strong acid (HCl).
- Since it is derived from a weak base and a strong acid, NH₄Cl is an acidic salt.
- Therefore, the pH of NH₄Cl solution will be **less than 7**.

3. **Analyze Sodium Carbonate (Na₂CO₃):**
- Sodium carbonate is formed from a strong base (NaOH) and a weak acid (H₂CO₃).
- Since it is derived from a strong base and a weak acid, Na₂CO₃ is a basic salt.
- Therefore, the pH of Na₂CO₃ solution will be **greater than 7**.

4. **Analyze Potassium Sulphate (K₂SO₄):**
- Potassium sulphate is formed from a strong base (KOH) and a strong acid (H₂SO₄).
- Since both the acid and base are strong, K₂SO₄ is a neutral salt.
- Therefore, the pH of K₂SO₄ solution will be **equal to 7**.

5. **Determine the order of pH:**
- From the analysis:
- NH₄Cl (pH < 7) is the most acidic.
- K₂SO₄ (pH = 7) is neutral.
- Na₂CO₃ (pH > 7) is the most basic.
- Thus, the correct order of pH from lowest to highest is:
- NH₄Cl < K₂SO₄ < Na₂CO₃

### Final Answer:
The correct order of pH for the solutions at 25°C is:
**NH₄Cl < K₂SO₄ < Na₂CO₃**

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