Which of the following salt have lowest pH ?

Options

A. `Na_(2)SO_(4)`
B. `(NH_(4))_(2)SO_(4)`
C. `Na_(2)CO_(3)`
D. NaCI

Answer

To determine which of the given salts has the lowest pH, we need to analyze the nature of each salt based on the acids and bases from which they are derived. Here’s a step-by-step solution:

### Step 1: Identify the salts and their components.
1. **Na2SO4**: This salt is formed from sodium hydroxide (NaOH), a strong base, and sulfuric acid (H2SO4), a strong acid.
2. **(NH4)2SO4**: This salt is formed from ammonium hydroxide (NH4OH), a weak base, and sulfuric acid (H2SO4), a strong acid.
3. **NaHCO3**: This salt is formed from sodium hydroxide (NaOH), a strong base, and carbonic acid (H2CO3), a weak acid.
4. **NaCl**: This salt is formed from sodium hydroxide (NaOH), a strong base, and hydrochloric acid (HCl), a strong acid.

### Step 2: Determine the pH of each salt.
1. **Na2SO4**: Since it is derived from a strong acid and a strong base, it will have a neutral pH (around 7).

2. **(NH4)2SO4**: This salt is derived from a strong acid (H2SO4) and a weak base (NH4OH). The presence of the strong acid will dominate, leading to an acidic solution with a pH less than 7.

3. **NaHCO3**: This salt is derived from a strong base (NaOH) and a weak acid (H2CO3). The solution will be basic, resulting in a pH greater than 7.

4. **NaCl**: Similar to Na2SO4, this salt is derived from a strong acid (HCl) and a strong base (NaOH), resulting in a neutral pH (around 7).

### Step 3: Compare the pH values.
- **Na2SO4**: Neutral pH (≈ 7)
- **(NH4)2SO4**: Acidic pH (< 7)
- **NaHCO3**: Basic pH (> 7)
- **NaCl**: Neutral pH (≈ 7)

### Conclusion:
Among the salts analyzed, **(NH4)2SO4** has the lowest pH because it is the only salt that results in an acidic solution.

### Final Answer:
**(NH4)2SO4** has the lowest pH.

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