pH of a 0.001 M NaOH solution will be

Options

A. 9
B. 3
C. 11
D. 12

Answer

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

### Step 1: Determine the concentration of OH⁻ ions
Since NaOH is a strong base, it completely dissociates in water. Therefore, the concentration of OH⁻ ions in a 0.001 M NaOH solution is also 0.001 M.

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

### Step 2: Calculate the pOH of the solution
The pOH can be calculated using the formula:

\[ \text{pOH} = -\log[\text{OH}^-] \]

Substituting the concentration of OH⁻:

\[ \text{pOH} = -\log(0.001) = -\log(10^{-3}) = 3 \]

### Step 3: Calculate the pH of the solution
We can find the pH using the relationship between pH and pOH:

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

Substituting the value of pOH:

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

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

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