The pH of a `0.001` M NaOH solution will be

Options

A. 3
B. 2
C. 11
D. 12

Answer

To find the pH of a 0.001 M NaOH solution, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the nature of NaOH**:
NaOH is a strong base, which means it completely dissociates in water. Therefore, the concentration of hydroxide ions (OH⁻) will be equal to the concentration of NaOH.

\[ \text{[OH⁻]} = 0.001 \, \text{M} = 10^{-3} \, \text{M} \]

2. **Calculate the pOH**:
The pOH can be calculated using the formula:

\[ \text{pOH} = -\log[\text{OH⁻}] \]

Substituting the concentration of hydroxide ions:

\[ \text{pOH} = -\log(10^{-3}) = 3 \]

3. **Use the relationship between pH and pOH**:
The relationship between pH and pOH at 25°C is given by:

\[ \text{pH} + \text{pOH} = 14 \]

Therefore, we can find the pH:

\[ \text{pH} = 14 - \text{pOH} = 14 - 3 = 11 \]

4. **Final Answer**:
The pH of a 0.001 M NaOH solution is **11**.