Equivalent weight of `H_(3)PO_(4)` in each of the reaction will be respectively - `H_(3)+OH^(-)rarrH_(2)PO_(4)+H_(2)`
`H_(3)PO_(4)+2OH^(-)rarrHPO_(4)^(2-)+2H_(2)O`
`H_(3)PO_(4)+2OH^(-)rarrPO_(4)^(3-)+3H_(2)O`

Options

A. `98,49,32.67`
B. `49,98,32.67`
C. `98,32.67,49`
D. `32.67,49,98`

Answer

To determine the equivalent weight of \( H_3PO_4 \) in the given reactions, we will follow these steps:

### Step 1: Calculate the Molecular Weight of \( H_3PO_4 \)
The molecular weight of \( H_3PO_4 \) can be calculated using the atomic weights of its constituent elements:
- Hydrogen (H): 1 g/mol
- Phosphorus (P): 31 g/mol
- Oxygen (O): 16 g/mol

The formula for \( H_3PO_4 \) is:
\[ \text{Molecular weight} = (3 \times 1) + (1 \times 31) + (4 \times 16) \]
Calculating this gives:
\[ \text{Molecular weight} = 3 + 31 + 64 = 98 \text{ g/mol} \]

### Step 2: Determine the Number of Replaceable \( H^+ \) Ions in Each Reaction
The equivalent weight of an acid is calculated using the formula:
\[ \text{Equivalent weight} = \frac{\text{Molecular weight}}{\text{Number of replaceable } H^+ \text{ ions}} \]

#### Reaction 1:
\[ H_3PO_4 + OH^- \rightarrow H_2PO_4^- + H_2 \]
In this reaction, one \( H^+ \) ion is replaced. Therefore, the number of replaceable \( H^+ \) ions = 1.

\[ \text{Equivalent weight} = \frac{98}{1} = 98 \text{ g/equiv} \]

#### Reaction 2:
\[ H_3PO_4 + 2OH^- \rightarrow HPO_4^{2-} + 2H_2O \]
In this reaction, two \( H^+ \) ions are replaced. Therefore, the number of replaceable \( H^+ \) ions = 2.

\[ \text{Equivalent weight} = \frac{98}{2} = 49 \text{ g/equiv} \]

#### Reaction 3:
\[ H_3PO_4 + 2OH^- \rightarrow PO_4^{3-} + 3H_2O \]
In this reaction, three \( H^+ \) ions are replaced. Therefore, the number of replaceable \( H^+ \) ions = 3.

\[ \text{Equivalent weight} = \frac{98}{3} \approx 32.67 \text{ g/equiv} \]

### Final Results
The equivalent weights of \( H_3PO_4 \) in the three reactions are:
1. For Reaction 1: 98 g/equiv
2. For Reaction 2: 49 g/equiv
3. For Reaction 3: 32.67 g/equiv

### Summary of Equivalent Weights
- Reaction 1: 98 g/equiv
- Reaction 2: 49 g/equiv
- Reaction 3: 32.67 g/equiv