How many moles of `H_2O` form when 25.0 mL of 0.10 M `HNO_3` solution is completely neutralised by NaOH?

Answer

To determine how many moles of \( H_2O \) are formed when 25.0 mL of 0.10 M \( HNO_3 \) solution is completely neutralized by NaOH, we can follow these steps:

### Step 1: Write the balanced chemical equation
The reaction between sodium hydroxide (NaOH) and nitric acid (HNO3) can be represented as:
\[ \text{NaOH} + \text{HNO}_3 \rightarrow \text{H}_2\text{O} + \text{NaNO}_3 \]
From the equation, we can see that 1 mole of \( HNO_3 \) reacts with 1 mole of \( NaOH \) to produce 1 mole of \( H_2O \).

### Step 2: Calculate the number of moles of \( HNO_3 \)
To find the number of moles of \( HNO_3 \) in the solution, we use the formula:
\[ \text{Number of moles} = \text{Molarity} \times \text{Volume (in liters)} \]
Given:
- Molarity of \( HNO_3 = 0.10 \, \text{M} \)
- Volume of \( HNO_3 = 25.0 \, \text{mL} = 25.0 \times 10^{-3} \, \text{L} \)

Now, substituting the values:
\[ \text{Number of moles of } HNO_3 = 0.10 \, \text{mol/L} \times 25.0 \times 10^{-3} \, \text{L} = 0.0025 \, \text{mol} \]

### Step 3: Determine the number of moles of \( H_2O \) produced
From the balanced equation, we see that 1 mole of \( HNO_3 \) produces 1 mole of \( H_2O \). Therefore, the number of moles of \( H_2O \) produced will be equal to the number of moles of \( HNO_3 \) used:
\[ \text{Number of moles of } H_2O = 0.0025 \, \text{mol} \]

### Final Answer
The number of moles of \( H_2O \) formed is:
\[ \boxed{0.0025 \, \text{mol}} \]

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