5.17 use the relationship between pressure and volume of a fixed mass of gas at constant temperature

P1 x V1 = P2 x V2

NOTE: this is sometimes written as P1 x V1 = constant

For example: A gas at a pressure of 250 kilopascals is compressed from a volume of 300cm3 down to a volume of 175cm3. The temperature of the gas does not change. Find the new pressure of the gas, in kilopascals.

Step 1: rearrange the equation to isolate one unknown

In this instance, we know P1, V1 and V2, and we are looking for P2. Therefore...

P2 = (P1 x V1) / V2

Step 2: substitute the known to find the unknown...

P2 = (250 x 300) / 175

P2 = 429 kPa (to 3 significant figures)

Example credit: CGP