A gas has a volume of 2.5 L at a pressure of 100 kPa. If the temperature is kept constant, what is the volume of the gas when the pressure is increased to 250 kPa?

This problem involves a change in pressure and volume of a gas at constant temperature, which is described by Boyle's Law: $P_1V_1 = P_2V_2$.

Given:
Initial volume, $V_1 = 2.5 \text{ L}$
Initial pressure, $P_1 = 100 \text{ kPa}$
Final pressure, $P_2 = 250 \text{ kPa}$
Final volume, $V_2 = ?$

$$250 \text{ kPa} \cdot \text{L} = (250 \text{ kPa})V_2$$ $$V_2 = \frac{250 \text{ kPa} \cdot \text{L}}{250 \text{ kPa}}$$ $$V_2 = 1.0 \text{ L}$$

The volume of the gas at $250 \text{ kPa}$ is $\boxed{\text{1.0 L}}$.