The equivalent mass of crystalline oxalic acid `( H_(2) C_(2) O_(4) . 2H_(2) O )` is equal to the equivalent weight of -

Options

A. `Na_(2) CO_(3)`
B. `HNO_(3)`
C. KOH
D. `CH_(3) COOH`

Answer

To find the equivalent mass of crystalline oxalic acid (H₂C₂O₄·2H₂O) and determine which substance has the same equivalent weight, we will follow these steps:

### Step 1: Determine the Molecular Weight of Crystalline Oxalic Acid
The molecular formula of crystalline oxalic acid is H₂C₂O₄·2H₂O. We need to calculate its molecular weight.

- **Molecular weight of H₂C₂O₄**:
- Hydrogen (H): 1 g/mol × 2 = 2 g/mol
- Carbon (C): 12 g/mol × 2 = 24 g/mol
- Oxygen (O): 16 g/mol × 4 = 64 g/mol

Total for H₂C₂O₄ = 2 + 24 + 64 = 90 g/mol

- **Molecular weight of 2H₂O**:
- Hydrogen (H): 1 g/mol × 4 = 4 g/mol
- Oxygen (O): 16 g/mol × 2 = 32 g/mol

Total for 2H₂O = 4 + 32 = 36 g/mol

- **Total Molecular Weight of H₂C₂O₄·2H₂O**:
- Total = 90 g/mol + 36 g/mol = 126 g/mol

### Step 2: Determine the Basicity of Oxalic Acid
The basicity of an acid is defined as the number of hydrogen ions (H⁺) that can be donated by one molecule of the acid. Oxalic acid can donate 2 protons (H⁺ ions), so its basicity is 2.

### Step 3: Calculate the Equivalent Mass of Oxalic Acid
The formula for equivalent mass is given by:

\[ \text{Equivalent Mass} = \frac{\text{Molecular Weight}}{\text{Basicity}} \]

Substituting the values we have:

\[ \text{Equivalent Mass} = \frac{126 \text{ g/mol}}{2} = 63 \text{ g/equiv} \]

### Step 4: Compare with Given Options
Now we need to check which of the given options has an equivalent mass of 63 g/equiv.

1. **Na₂CO₃**:
- Molecular weight = (23×2) + (12) + (16×3) = 46 + 12 + 48 = 106 g/mol
- Basicity = 2 (it can donate 2 Na⁺ ions)
- Equivalent mass = 106 g/mol / 2 = 53 g/equiv

2. **HNO₃**:
- Molecular weight = 1 + 14 + (16×3) = 1 + 14 + 48 = 63 g/mol
- Basicity = 1 (it can donate 1 H⁺ ion)
- Equivalent mass = 63 g/mol / 1 = 63 g/equiv

3. **Other options** (not calculated, but given in the transcript):
- Equivalent mass = 56 g/equiv and 60 g/equiv respectively.

### Conclusion
The equivalent mass of crystalline oxalic acid (63 g/equiv) is equal to the equivalent weight of **HNO₃**.