0.126 g of acid required 20 mL of 0.1 N NaOH for complete neutralisation. The equivalent mass of an acid is

Options

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

Explanation

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

### Step 1: Understand the given data
We are given:
- Mass of acid = 0.126 g
- Volume of NaOH = 20 mL
- Normality of NaOH = 0.1 N

### Step 2: Convert volume of NaOH from mL to L
To convert the volume from mL to L, we use the conversion factor \(1 \, \text{L} = 1000 \, \text{mL}\):
\[ \text{Volume of NaOH in L} = \frac{20 \, \text{mL}}{1000} = 0.020 \, \text{L} \]

### Step 3: Calculate the number of equivalents of NaOH
Normality (N) is defined as equivalents per liter. Therefore, the number of equivalents of NaOH can be calculated as:
\[ \text{Equivalents of NaOH} = \text{Normality} \times \text{Volume in L} = 0.1 \, \text{N} \times 0.020 \, \text{L} = 0.002 \, \text{equivalents} \]

### Step 4: Use the equivalence principle
In a neutralization reaction, the equivalents of the acid will be equal to the equivalents of the base. Thus, the equivalents of the acid is also:
\[ \text{Equivalents of acid} = 0.002 \, \text{equivalents} \]

### Step 5: Calculate the equivalent mass of the acid
The equivalent mass (or equivalent weight) of the acid can be calculated using the formula:
\[ \text{Equivalent mass} = \frac{\text{Mass of acid}}{\text{Equivalents of acid}} = \frac{0.126 \, \text{g}}{0.002 \, \text{equivalents}} = 63 \, \text{g/equiv} \]

### Conclusion
The equivalent mass of the acid is **63 g/equiv**.

---