What volume of 0.1M sodium hydroxide solution :a, contains 0.0025mole of sodium hydroxide?

Molarity ($M$) is defined as moles of solute per liter of solution.

$$M = \frac{\text{moles of solute}}{\text{volume of solution (L)}}$$

Given:
Moles of sodium hydroxide = 0.0025 mol
Molarity of sodium hydroxide solution = 0.1 M

$$\text{volume of solution (L)} = \frac{0.0025 \text{ mol}}{0.1 \text{ M}}$$ $$\text{volume of solution (L)} = 0.025 \text{ L}$$

$$\text{volume of solution (mL)} = 0.025 \text{ L} \times \frac{1000 \text{ mL}}{1 \text{ L}}$$ $$\text{volume of solution (mL)} = 25 \text{ mL}$$

The volume of 0.1 M sodium hydroxide solution that contains 0.0025 mole of sodium hydroxide is $\boxed{\text{0.025 L}}$ or $\boxed{\text{25 mL}}$.