The volume of a sample of hydrogen gas was decreased from 12.85 L to 6.14 L at constant temperature. If the final pressure exerted by the hydrogen gas sample was 7.40 atm, what pressure did the hydrogen gas exert before its volume was decreased?

Answer: 3.79 atm Explanation: Assuming ideal behavior, the gas sample should satisfy the Boyle's law, which states that P ⋅ V = a constant when temperature is held constant. [1] In other words, the pressure the gas exerts is inversely related to the volume of the airtight container. Therefore P 1 ⋅ V 1 = P 2 ⋅ V 2 P 1 = P 2 ⋅ V 2 V 1 = P 2 ⋅ V 2 V 1 Evaluate with V 1 = 13.16 L, V 2 = 6.45 L, P 2 = 7.73 atm as given in the question: P 1 = 7.73 atm ⋅ 6.45 L 13.16 L = 3.79 atm (rounded to three significant figures)