Which of the following combinations will make a buffer solution ?
(i) `CH_(3)COONa(2 mol)+HCI(1mol)`
(ii) `CH_(3)COOH(2mol)+NaOH(1mol)`
(iii) `CH_(3)COOH(1mol)+CH_(3)COONa(1mol)`

Options

A. (iii)
B. (i),(ii)
C. (ii), (iii)
D. (i), (ii), (iii)

Explanation

To determine which combinations will make a buffer solution, we need to understand what a buffer solution is. A buffer solution is typically composed of a weak acid and its conjugate base or a weak base and its conjugate acid.

Let's analyze each option step by step:

### Step 1: Analyze Option (i) `CH₃COONa (2 mol) + HCl (1 mol)`

1. **Identify the components**:
- Sodium acetate (CH₃COONa) is the salt of acetic acid (CH₃COOH), which is a weak acid.
- Hydrochloric acid (HCl) is a strong acid.

2. **Reaction**:
- When HCl reacts with sodium acetate, it will convert some of the acetate ions into acetic acid:
\[ CH₃COO^- + HCl \rightarrow CH₃COOH + Cl^- \]
- Here, 1 mole of HCl will react with 1 mole of acetate ions.

3. **Final concentrations**:
- Starting with 2 moles of sodium acetate and 1 mole of HCl, after the reaction:
- Acetic acid produced: 1 mole
- Remaining sodium acetate: 2 - 1 = 1 mole
- We are left with 1 mole of acetic acid and 1 mole of sodium acetate.

4. **Conclusion**: This combination will form a buffer solution.

### Step 2: Analyze Option (ii) `CH₃COOH (2 mol) + NaOH (1 mol)`

1. **Identify the components**:
- Acetic acid (CH₃COOH) is a weak acid.
- Sodium hydroxide (NaOH) is a strong base.

2. **Reaction**:
- When NaOH reacts with acetic acid, it will convert some of the acetic acid into sodium acetate:
\[ CH₃COOH + NaOH \rightarrow CH₃COONa + H₂O \]
- Here, 1 mole of NaOH will react with 1 mole of acetic acid.

3. **Final concentrations**:
- Starting with 2 moles of acetic acid and 1 mole of NaOH, after the reaction:
- Sodium acetate produced: 1 mole
- Remaining acetic acid: 2 - 1 = 1 mole
- We are left with 1 mole of acetic acid and 1 mole of sodium acetate.

4. **Conclusion**: This combination will also form a buffer solution.

### Step 3: Analyze Option (iii) `CH₃COOH (1 mol) + CH₃COONa (1 mol)`

1. **Identify the components**:
- Acetic acid (CH₃COOH) is a weak acid.
- Sodium acetate (CH₃COONa) is the salt of acetic acid.

2. **Final concentrations**:
- We have 1 mole of acetic acid and 1 mole of sodium acetate already present.

3. **Conclusion**: This combination will also form a buffer solution.

### Final Conclusion:
All three combinations (i), (ii), and (iii) will make a buffer solution.