STATEMENT-1 : In the given reaction, `NaOH+H_(3)PO_(4)rarr NaH_(2)PO_(4)+H_(2)O` equivalent mass of `H_(3)PO_(4)` is `M//3`
STATEMENT-2 : `H_(3)PO_(4)` is tribasic acid.

Options

A. If both the statement are TRUE and STATEMENT -2 is the correct explanation of STATEMENT-1
B. If both the statement are TRUE but STATEMENT-2 is NOT the correct explanation of STATEMENT-1
C. If STATEMENT- is 1 TRUE and STATEMENT-2 is FALSE
D. If STATEMENT-1 is FALSE and STATEMENT-2 is TRUE

Answer

To solve the problem, we will analyze both statements provided and determine their validity step-by-step.

### Step 1: Understanding the Reaction
The reaction given is:
\[ \text{NaOH} + \text{H}_3\text{PO}_4 \rightarrow \text{NaH}_2\text{PO}_4 + \text{H}_2\text{O} \]

### Step 2: Identifying the Acid and Its Properties
In this reaction, \( \text{H}_3\text{PO}_4 \) (phosphoric acid) is acting as an acid. It can donate protons (H⁺ ions) to the base (NaOH).

### Step 3: Determining the Equivalent Mass
The equivalent mass of an acid is calculated using the formula:
\[ \text{Equivalent mass} = \frac{\text{Molecular mass}}{n} \]
where \( n \) is the number of replaceable H⁺ ions (or OH⁻ ions for bases).

### Step 4: Finding the n Factor for \( \text{H}_3\text{PO}_4 \)
- \( \text{H}_3\text{PO}_4 \) is a tribasic acid, meaning it can donate up to 3 H⁺ ions.
- In the reaction, \( \text{H}_3\text{PO}_4 \) donates 1 H⁺ ion to form \( \text{NaH}_2\text{PO}_4 \). Therefore, in this specific reaction, the n factor is 1.

### Step 5: Calculating the Equivalent Mass of \( \text{H}_3\text{PO}_4 \)
Given that the molecular mass of \( \text{H}_3\text{PO}_4 \) is \( M \):
\[ \text{Equivalent mass} = \frac{M}{n} = \frac{M}{1} = M \]

### Step 6: Evaluating Statement 1
Statement 1 claims that the equivalent mass of \( \text{H}_3\text{PO}_4 \) is \( \frac{M}{3} \). Since we calculated it to be \( M \), this statement is **incorrect**.

### Step 7: Evaluating Statement 2
Statement 2 states that \( \text{H}_3\text{PO}_4 \) is a tribasic acid. Since it can donate 3 H⁺ ions, this statement is **correct**.

### Conclusion
- Statement 1 is false.
- Statement 2 is true.

Thus, the correct option is that Statement 1 is incorrect and Statement 2 is correct.