pH of 0.1 N NaOH(aq) solution

Options

A. 2.7
B. 4.7
C. 7
D. 13

Answer

To find the pH of a 0.1 N NaOH aqueous solution, we can follow these steps:

### Step 1: Understand Normality and Molarity
Normality (N) is related to molarity (M) through the equation:
\[ \text{Normality} = \text{Molarity} \times n \]
where \( n \) is the number of equivalents. For NaOH, which is a strong base, it dissociates completely to give one hydroxide ion (OH⁻) per molecule. Therefore, the n factor for NaOH is 1.

### Step 2: Convert Normality to Molarity
Since the n factor for NaOH is 1, the normality is equal to the molarity:
\[ \text{Molarity} = 0.1 \, N = 0.1 \, M \]

### Step 3: Determine the Concentration of OH⁻ Ions
In a 0.1 M NaOH solution, the concentration of hydroxide ions (OH⁻) is also 0.1 M because NaOH completely dissociates:
\[ \text{[OH⁻]} = 0.1 \, M \]

### Step 4: Calculate pOH
To find the pOH, we use the formula:
\[ \text{pOH} = -\log[\text{OH⁻}] \]
Substituting the concentration of OH⁻:
\[ \text{pOH} = -\log(0.1) = 1 \]

### Step 5: Calculate pH
We know that:
\[ \text{pH} + \text{pOH} = 14 \]
Thus, we can find the pH:
\[ \text{pH} = 14 - \text{pOH} = 14 - 1 = 13 \]

### Final Answer
The pH of a 0.1 N NaOH aqueous solution is **13**.

---