Boyle’s Law
Boyle’s Law can be used to compare changing conditions for a gas. We use
This equation can be used to calculate any one of the four quantities if the other three are known.
Sample Problem: Boyle’s Law
A sample of oxygen gas has a volume of 425 mL when the pressure is equal to 387 kPa. The gas is allowed to expand into a 1.75 L container. Calculate the new pressure of the gas.
Step 1: List the known quantities and plan the problem.
Known

P1=387 kPa 
V1=425 mL 
V2=1.75 L=1750 mL
Unknown

P2=? kPa
Use Boyle’s Law to solve for the unknown pressure
Step 2: Solve.
First, rearrange the equation algebraically to solve for
Now substitute the known quantities into the equation and solve.
Step 3: Think about your result.
The volume has increased to slightly over 4 times its original value and so the pressure is decreased by about
Summary
 The volume of a gas is inversely proportional to pressure.