Assertion (A): On mixing equal volumes of `1M HCi` and `2 M CH_(3)COONa`, an acidic buffer solution is formed.
Reason (R) : The resultant mixture contains `CH_(3)COOH` and `CH_(3)COONa` which are parts of acidic buffer.

Options

A. If both (A) and (R) are correc, and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect, but (R) is correct.

Explanation

To solve the question, we need to analyze the assertion and the reason given:

**Assertion (A):** On mixing equal volumes of 1M HCl and 2M CH₃COONa, an acidic buffer solution is formed.
**Reason (R):** The resultant mixture contains CH₃COOH and CH₃COONa which are parts of the acidic buffer.

### Step-by-Step Solution:

1. **Understanding the Components:**
- We have two solutions: 1M HCl (a strong acid) and 2M CH₃COONa (sodium acetate, a salt of a weak acid).
- HCl will dissociate completely in solution to give H⁺ and Cl⁻ ions.
- Sodium acetate will dissociate to give CH₃COO⁻ (acetate ions) and Na⁺ ions.

2. **Calculating Moles:**
- When equal volumes (let's say V liters) of these solutions are mixed:
- Moles of H⁺ from HCl = 1M × V = V moles.
- Moles of CH₃COO⁻ from CH₃COONa = 2M × V = 2V moles.

3. **Reaction Between H⁺ and CH₃COO⁻:**
- The acetate ions (CH₃COO⁻) will react with the H⁺ ions to form acetic acid (CH₃COOH):
\[ \text{CH}_3\text{COO}^- + \text{H}^+ \rightarrow \text{CH}_3\text{COOH} \]
- Since we have V moles of H⁺ and 2V moles of CH₃COO⁻, all the H⁺ will react:
- After the reaction, we will have:
- Moles of CH₃COOH = V moles (produced from the reaction).
- Moles of CH₃COO⁻ remaining = 2V - V = V moles.

4. **Final Composition of the Mixture:**
- The resultant mixture will contain:
- V moles of CH₃COOH (acetic acid).
- V moles of CH₃COO⁻ (acetate ions).
- This combination of a weak acid (CH₃COOH) and its conjugate base (CH₃COO⁻) constitutes an acidic buffer solution.

5. **Conclusion:**
- Since the mixture contains both CH₃COOH and CH₃COO⁻, it confirms that an acidic buffer solution is formed.
- Therefore, both the assertion and the reason are correct, and the reason correctly explains the assertion.

### Final Answer:
- The assertion (A) is true, and the reason (R) is also true and provides the correct explanation for the assertion.