An aqueous solutions of 1 M NaCl and 1 M HCl is :

Options

A. not a buffer but `pH lt 7`
B. not a buffer but `pH gt 7`
C. a buffer with `pH lt 7`
D. a buffer with `pH gt 7`

Explanation

To determine whether an aqueous solution of 1 M NaCl and 1 M HCl is a buffer, we need to analyze the components of the solution and their properties.

### Step-by-Step Solution:

1. **Identify the Components**:
- The solution contains 1 M NaCl and 1 M HCl.
- NaCl is a salt formed from the strong base NaOH and the strong acid HCl.
- HCl is a strong acid.

2. **Understand the Nature of NaCl**:
- NaCl is a neutral salt because it is derived from a strong acid (HCl) and a strong base (NaOH).
- In solution, NaCl dissociates into Na⁺ and Cl⁻ ions, which do not affect the pH significantly.

3. **Analyze HCl**:
- HCl is a strong acid that completely dissociates in water to produce H⁺ ions.
- The concentration of H⁺ ions in the solution will be equal to the concentration of HCl, which is 1 M.

4. **Determine if the Solution is a Buffer**:
- A buffer solution typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
- In this case, we have a strong acid (HCl) and a neutral salt (NaCl), which does not provide a weak acid or weak base.
- Therefore, this combination does not meet the criteria for a buffer solution.

5. **Conclusion on pH**:
- Since HCl is a strong acid, the pH of the solution will be less than 7.
- The pH can be calculated using the formula:
\[ \text{pH} = -\log[H^+] \]
- For a 1 M HCl solution:
\[ \text{pH} = -\log(1) = 0 \]
- Thus, the pH is significantly less than 7, confirming that the solution is acidic.

### Final Answer:
The aqueous solution of 1 M NaCl and 1 M HCl is **not a buffer**, and the pH of the solution is **less than 7**.

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