# What is an example of a Boyle's law practice problem?

Jul 16, 2014

Boyle's Law, a principle that describes the relationship between the pressure and volume of a gas. According to this law, the pressure exerted by a gas held at a constant temperature varies inversely with the volume of the gas. For example, if the volume is halved, the pressure is doubled; and if the volume is doubled, the pressure is halved. The reason for this effect is that a gas is made up of loosely spaced molecules moving at random. If a gas is compressed in a container, these molecules are pushed together; thus, the gas occupies less volume. The molecules, having less space in which to move, hit the walls of the container more frequently and thus exert an increased pressure.

Stated as a formula, Boyle's Law reads:

${V}_{1}$/ ${V}_{2}$= ${P}_{2}$/ ${P}_{1}$ (at constant temperature)

where ${V}_{1}$ equals the original volume, ${V}_{2}$ equals the new volume, ${P}_{1}$ the original pressure, and ${P}_{2}$ the new pressure.

An unknown gas has an initial pressure of 150 kPa and a volume of 1 L. If the volume is increased to 1.5 L, what will the pressure be now?
${V}_{1}$ = 1L ${P}_{1}$ = 150 kPa
${V}_{2}$= 1.5 L ${P}_{2}$ = ?

1L/ 1.5 L = ${P}_{2}$ / 150 kPa

${P}_{2}$ = 150 kPa x 1 L / 1.5 L

${P}_{2}$ = 100 kPa.