pH of a `10^(-3)M` NaCl solution (aq) at `25^@C` is

Options

A. 7
B. 11
C. 3
D. all wrong

Answer

To find the pH of a \(10^{-3} M\) NaCl solution at \(25^\circ C\), we can follow these steps:

### Step 1: Understand the nature of NaCl
NaCl is a salt formed from the neutralization of a strong acid (HCl) and a strong base (NaOH). In aqueous solution, NaCl dissociates completely into Na\(^+\) and Cl\(^-\) ions. Since both ions do not hydrolyze in water, NaCl is considered a neutral salt.

### Step 2: Determine the effect of NaCl on pH
Since NaCl does not affect the concentration of H\(^+\) or OH\(^-\) ions in the solution, the solution remains neutral. In pure water at \(25^\circ C\), the concentration of H\(^+\) ions is \(1 \times 10^{-7} M\).

### Step 3: Calculate the pH
The pH is calculated using the formula:
\[ \text{pH} = -\log[H^+] \]
In pure water, the concentration of H\(^+\) ions is \(1 \times 10^{-7} M\):
\[ \text{pH} = -\log(1 \times 10^{-7}) = 7 \]

### Conclusion
Thus, the pH of a \(10^{-3} M\) NaCl solution at \(25^\circ C\) is **7**.

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