Which among the following is an acidic buffer?

Options

A. `CH_3COOH + HCI`
B. `CH_3COOH + CH_3COONa`
C. `HCI + H_2SO_4`
D. `NH_4OH + NaOH`

Answer

To determine which among the given options is an acidic buffer, we need to understand what an acidic buffer is. An acidic buffer is a solution that consists of a weak acid and its conjugate base (which is usually the salt of the weak acid with a strong base).

Let's analyze each option step by step:

1. **Option A: CH3COOH + HCl**
- CH3COOH (acetic acid) is a weak acid.
- HCl (hydrochloric acid) is a strong acid.
- This combination does not form a buffer because it consists of a weak acid and a strong acid, not a weak acid and its conjugate base.

2. **Option B: CH3COOH + CH3COONa**
- CH3COOH (acetic acid) is a weak acid.
- CH3COONa (sodium acetate) is the salt of acetic acid, which provides the conjugate base (CH3COO^-).
- This combination forms an acidic buffer because it contains a weak acid and its conjugate base.

3. **Option C: HCl + H2SO4**
- HCl (hydrochloric acid) is a strong acid.
- H2SO4 (sulfuric acid) is also a strong acid.
- This combination does not form a buffer because it consists of two strong acids.

4. **Option D: NH4OH + NaOH**
- NH4OH (ammonium hydroxide) is a weak base.
- NaOH (sodium hydroxide) is a strong base.
- This combination does not form a buffer because it consists of a weak base and a strong base.

After analyzing all the options, we can conclude that the only combination that forms an acidic buffer is:

**Correct Answer: Option B: CH3COOH + CH3COONa**