Equivalent weight of `H_(3) PO_(2)` is (`M rarr` molecular weight)

Options

A. `(M)/(1)`
B. `(M)/(2)`
C. `(M)/(3)`
D. `(M)/(4)`

Answer

To find the equivalent weight of \( H_3PO_2 \) (phosphorous acid), we will follow these steps:

### Step 1: Identify the Molecular Weight
The molecular weight (M) of \( H_3PO_2 \) is the sum of the atomic weights of all the atoms in the molecule.

- Hydrogen (H) has an atomic weight of approximately 1 g/mol.
- Phosphorus (P) has an atomic weight of approximately 31 g/mol.
- Oxygen (O) has an atomic weight of approximately 16 g/mol.

Calculating the molecular weight:
\[ M = (3 \times 1) + (1 \times 31) + (2 \times 16) = 3 + 31 + 32 = 66 \text{ g/mol} \]

### Step 2: Determine the n-factor
The n-factor of an acid is defined as the number of moles of hydrogen ions (H\(^+\)) that can be provided by one mole of the acid.

For \( H_3PO_2 \):
- It is a monobasic acid, meaning it can donate one proton (H\(^+\)) per molecule.
- Therefore, the n-factor of \( H_3PO_2 \) is 1.

### Step 3: Calculate the Equivalent Weight
The formula for equivalent weight is given by:
\[ \text{Equivalent Weight} = \frac{\text{Molecular Weight}}{\text{n-factor}} \]

Substituting the values:
\[ \text{Equivalent Weight} = \frac{M}{1} = M \]

### Conclusion
Thus, the equivalent weight of \( H_3PO_2 \) is equal to its molecular weight (M).

### Final Answer
The equivalent weight of \( H_3PO_2 \) is \( M \).

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