A fixed sample of hydrogen occupies 2 L at 200 kPa. What is its volume at 400 kPa if temperature is constant? Assume ideal-gas behavior.

A) 1 L

B) 2 L

C) 4 L

D) 0.5 L

Answer: A

Explanation: Boyle’s law keeps pressure times volume constant for fixed gas amount and temperature. The pressure doubles from 200 to 400 kPa, so 2 L becomes 1 L.