If 1 mole of `H_(3)PO_(4)` reacts with 1 mole of `X(OH)_(2)` as shown below :
`H_(3)PO_(4)+X(OH)_(2) to XHPO_(4)+2H_(2)O " then"`

Options

A. the equivalent mass of base is `(mol.mass)/(2)`
B. the eq. mass of `H_(3)PO_(4)` is `(98)/(3)`
C. the resulting solution requires 1 mole NaOH for complete neutralization
D. minimum 1 mole of X`(OH)_(2)` is required for complete neutralization of `XHPO_(4)`

Answer

To solve the problem, we need to analyze the reaction between phosphoric acid (H₃PO₄) and the base X(OH)₂, and determine the correct statements regarding equivalent masses and neutralization.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction given is:
\[ H_3PO_4 + X(OH)_2 \rightarrow XHPO_4 + 2H_2O \]
This indicates that 1 mole of H₃PO₄ reacts with 1 mole of X(OH)₂ to produce 1 mole of XHPO₄ and 2 moles of water.

2. **Calculate the Equivalent Mass of X(OH)₂**:
- The equivalent mass is calculated using the formula:
\[ \text{Equivalent mass} = \frac{\text{Molar mass}}{\text{Valency factor}} \]
- For X(OH)₂, the valency factor is 2 because it can donate 2 OH⁻ ions.
- Therefore, the equivalent mass of X(OH)₂ is:
\[ \text{Equivalent mass of } X(OH)_2 = \frac{M}{2} \]
- This statement is correct.

3. **Calculate the Equivalent Mass of H₃PO₄**:
- The molar mass of H₃PO₄ is approximately 98 g/mol.
- H₃PO₄ can donate a maximum of 3 H⁺ ions (basicity = 3), but in this reaction, it donates only 2 H⁺ ions.
- Thus, the valency factor for this reaction is 2.
- The equivalent mass of H₃PO₄ is:
\[ \text{Equivalent mass of } H_3PO_4 = \frac{98}{2} = 49 \text{ g/equiv} \]
- The statement claiming the equivalent mass is 98/3 is incorrect.

4. **Determine Neutralization Requirements**:
- The resulting solution is XHPO₄. To neutralize XHPO₄, it will react with NaOH:
\[ XHPO_4 + NaOH \rightarrow NaXPO_4 + H_2O \]
- This indicates that 1 mole of XHPO₄ requires 1 mole of NaOH for complete neutralization. Thus, this statement is correct.

5. **Determine Minimum Requirement of X(OH)₂ for Neutralization**:
- To neutralize XHPO₄, we need to consider the reaction:
\[ XHPO_4 + X(OH)_2 \rightarrow \text{Products} \]
- Since 1 mole of XHPO₄ requires 1 mole of X(OH)₂ for neutralization, the statement that it requires a minimum of 1 mole of X(OH)₂ is incorrect. It actually requires only half a mole of X(OH)₂ for complete neutralization.

### Conclusion:
The correct statements from the options provided are:
- A: The equivalent mass of the base is molar mass by 2. (Correct)
- C: Resulting solution requires 1 mole NaOH for complete neutralization. (Correct)