For which of the following compound equivalent weight is equal to molecular weight

Options

A. `H_(2)SO_(4)`
B. `H_(3)PO_(2)`
C. `H_(3)PO_(4)`
D. `H_(3)PO_(3)`

Explanation

To determine which compound has an equivalent weight equal to its molecular weight, we need to understand the concept of equivalent weight and the n-factor.

### Step-by-Step Solution:

1. **Understanding Equivalent Weight**:
Equivalent weight is defined as the molecular weight divided by the n-factor. The formula is:
\[ \text{Equivalent Weight} = \frac{\text{Molecular Weight}}{n \text{-factor}} \]
For equivalent weight to equal molecular weight, the n-factor must be 1.

2. **Identifying n-factor**:
The n-factor for acids is determined by the number of H⁺ ions that can be replaced or donated. We will analyze each compound provided in the question to find their n-factors.

3. **Analyzing H₂SO₄ (Sulfuric Acid)**:
- Structure: H₂SO₄ has two replaceable H⁺ ions.
- n-factor = 2 (since it can donate 2 H⁺ ions).
- Conclusion: H₂SO₄ does not have an n-factor of 1.

4. **Analyzing H₃PO₂ (Phosphorous Acid)**:
- Structure: H₃PO₂ has one replaceable H⁺ ion.
- n-factor = 1 (only one H⁺ can be replaced).
- Conclusion: H₃PO₂ has an n-factor of 1.

5. **Analyzing H₃PO₄ (Phosphoric Acid)**:
- Structure: H₃PO₄ has three replaceable H⁺ ions.
- n-factor = 3 (it can donate 3 H⁺ ions).
- Conclusion: H₃PO₄ does not have an n-factor of 1.

6. **Analyzing H₃PO₃ (Phosphorous Acid)**:
- Structure: H₃PO₃ has two replaceable H⁺ ions.
- n-factor = 2 (it can donate 2 H⁺ ions).
- Conclusion: H₃PO₃ does not have an n-factor of 1.

7. **Final Conclusion**:
The only compound among the options that has an n-factor of 1 is H₃PO₂. Therefore, the equivalent weight of H₃PO₂ is equal to its molecular weight.

### Answer:
H₃PO₂ (Phosphorous Acid) is the compound for which the equivalent weight is equal to the molecular weight.