In the reaction `CA(OH)_(2)+H_(3)PO_(4) rarr Ca_(3)(PO_(4))_(2)+H_(2)O`, the equivalent mass of `H_(2)`O is: (M molecular mass)

Options

A. (a)M
B. (b)M/2
C. (c )M/3
D. (d)M/6

Explanation

To find the equivalent mass of water (H₂O) in the given reaction, we can follow these steps:

### Step 1: Understand the Reaction
The reaction provided is:
\[ \text{Ca(OH)}_2 + \text{H}_3\text{PO}_4 \rightarrow \text{Ca}_3(\text{PO}_4)_2 + \text{H}_2\text{O} \]

This is a neutralization reaction where calcium hydroxide reacts with phosphoric acid to produce calcium phosphate and water.

### Step 2: Identify the Role of Water
In this neutralization reaction, water (H₂O) is formed from the combination of hydrogen ions (H⁺) from the acid and hydroxide ions (OH⁻) from the base.

### Step 3: Determine the n-factor of Water
The n-factor of a substance in a reaction is defined as the number of moles of H⁺ ions or OH⁻ ions that one mole of the substance can neutralize or produce.

For water (H₂O):
- It is formed from one H⁺ ion and one OH⁻ ion.
- Therefore, the n-factor of water is 1.

### Step 4: Calculate the Equivalent Mass
The equivalent mass (or equivalent weight) of a substance can be calculated using the formula:
\[ \text{Equivalent Mass} = \frac{\text{Molecular Mass}}{\text{n-factor}} \]

For water:
- The molecular mass of water (H₂O) is approximately 18 g/mol.
- Since the n-factor of water is 1, we can substitute these values into the formula.

Thus, the equivalent mass of water is:
\[ \text{Equivalent Mass of H}_2\text{O} = \frac{18 \, \text{g/mol}}{1} = 18 \, \text{g} \]

### Final Answer
The equivalent mass of H₂O is equal to its molecular mass, which is \( M \).