Boyle’s Law is a special case of the ideal gas law in which the pressure and volume of an ideal gas are inversely proportional to each other, providing the temperature and mass of the gas are held constant. Here’s an example of how to perform a calculation using Boyle’s Law.

Boyle’s Law Review

Pressure P and Volume V are inversely proportional when Temperature T and mass n are held constant:

P ∝ 1/V where V changes by a factor of z

P_{final} = 1/z x V_{initial}

Example Problem

For example, calculate the final volume of a gas if the pressure of a 4.0 L sample is changed from 2.5 atm to 5.0 atm.

You calculate z = P_{final}/P_{initial} z = 5.0 / 2.5 z = 2

P_{final} = 1/z x V_{initial} P_{final} = 1/2 x 4.0 L P_{final} = 2.0 L