Which will act as a buffer solution

Options

A. `200 mol N//10 NaOH+ 100ml N//20 HCl`
B. `100ml 0.1 N NaOH + 100 ml 0.1 N HCl`
C. `100 mol 0.1 N NaOH+50 ml 0.2 N CH_(3)COOH`
D. `100 ml 0.1 N NaOH + 150 ml 0.1 N HCN`

Explanation

To determine which solution acts as a buffer, we need to understand what a buffer solution is. A buffer solution is one that resists changes in pH when small amounts of acid or base are added. Typically, a buffer solution consists of a weak acid and its conjugate base or a weak base and its conjugate acid.

### Step-by-Step Solution:

1. **Identify Components of Potential Buffer Solutions**:
- Look at the given options for the solutions. Common examples of buffer solutions include acetic acid (weak acid) with sodium acetate (conjugate base) or ammonia (weak base) with ammonium chloride (conjugate acid).

2. **Check for Weak Acid and Conjugate Base Pair**:
- For each option, check if it contains a weak acid and its conjugate base. For example, if you have acetic acid (CH₃COOH) and sodium acetate (CH₃COONa), this would be a buffer.

3. **Check for Weak Base and Conjugate Acid Pair**:
- Similarly, check if any option contains a weak base and its conjugate acid. For example, ammonia (NH₃) and ammonium chloride (NH₄Cl) would also form a buffer solution.

4. **Evaluate pH Stability**:
- Consider the ability of the solution to maintain a stable pH. A buffer solution will maintain its pH when small amounts of strong acids or bases are added.

5. **Conclusion**:
- After evaluating the options, identify which one meets the criteria of having a weak acid and its conjugate base or a weak base and its conjugate acid. This will be your buffer solution.