The compound whose 0.1 M solution is acidic :

Options

A. Ammonium formate
B. Ammonium sulphate
C. Ammonium chloride
D. Sodium formate

Answer

To determine which compound has a 0.1 M solution that is acidic, we need to analyze each compound's behavior when dissolved in water. Let's go through the options step by step.

### Step 1: Analyze Ammonium Formate (HCOONH4)
- When ammonium formate is dissolved in water, it dissociates into formic acid (HCOOH) and ammonium hydroxide (NH4OH).
- Formic acid is a weak acid, and ammonium hydroxide is a weak base.
- Since both the acid and base are weak, the solution will be neutral.

**Conclusion**: Ammonium formate does not produce an acidic solution.

### Step 2: Analyze Ammonium Sulfate (NH4)2SO4
- When ammonium sulfate is dissolved in water, it dissociates into ammonium ions (NH4+) and sulfate ions (SO4^2-).
- The ammonium ion (NH4+) can react with water to form ammonium hydroxide (NH4OH) and release H+ ions, which makes the solution acidic.
- Sulfuric acid (H2SO4) is a strong acid, which will also contribute to the acidity of the solution.

**Conclusion**: Ammonium sulfate produces an acidic solution.

### Step 3: Analyze Ammonium Chloride (NH4Cl)
- When ammonium chloride is dissolved in water, it dissociates into ammonium ions (NH4+) and chloride ions (Cl-).
- The ammonium ion (NH4+) can react with water to form ammonium hydroxide (NH4OH) and release H+ ions, making the solution acidic.
- Hydrochloric acid (HCl) is a strong acid, which will also contribute to the acidity of the solution.

**Conclusion**: Ammonium chloride produces an acidic solution.

### Step 4: Analyze Sodium Formate (HCOONa)
- When sodium formate is dissolved in water, it dissociates into sodium ions (Na+) and formate ions (HCOO-).
- The formate ion (HCOO-) can react with water to form formic acid (HCOOH) and hydroxide ions (OH-), making the solution basic.

**Conclusion**: Sodium formate does not produce an acidic solution.

### Final Conclusion
The compounds that produce an acidic solution when dissolved in water are:
- Ammonium sulfate (B)
- Ammonium chloride (C)

Thus, the correct answer is **B and C**.

---