0.52 g of a dibasic acid required 100 mL of 0.2 N NaOH for complete neutralization. The equivalent weight of acid is:

Options

A. 26
B. 52
C. 104
D. 156

Explanation

To find the equivalent weight of the dibasic acid, we can follow these steps:

### Step 1: Understand the Concept of Normality
Normality (N) is defined as the number of equivalents of solute per liter of solution. In this case, we are dealing with a dibasic acid, which means it can donate two protons (H⁺ ions) per molecule.

### Step 2: Calculate the Number of Equivalents of NaOH
We know that:
- Normality of NaOH = 0.2 N
- Volume of NaOH = 100 mL = 0.1 L

To find the number of equivalents of NaOH used:
\[ \text{Number of equivalents of NaOH} = \text{Normality} \times \text{Volume (in L)} = 0.2 \, \text{N} \times 0.1 \, \text{L} = 0.02 \, \text{equivalents} \]

### Step 3: Relate the Equivalents of Acid to the Equivalents of Base
Since the acid is dibasic, it will provide two equivalents per mole. Therefore, the number of equivalents of the dibasic acid will also be equal to the number of equivalents of NaOH used for neutralization:
\[ \text{Number of equivalents of acid} = 0.02 \, \text{equivalents} \]

### Step 4: Calculate the Equivalent Weight of the Acid
The equivalent weight of a substance is given by the formula:
\[ \text{Equivalent weight} = \frac{\text{Weight of the substance}}{\text{Number of equivalents}} \]
Given that the weight of the dibasic acid is 0.52 g, we can substitute the values:
\[ \text{Equivalent weight of acid} = \frac{0.52 \, \text{g}}{0.02 \, \text{equivalents}} = 26 \, \text{g/equiv} \]

### Final Answer
The equivalent weight of the dibasic acid is **26 g/equiv**.

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