Boyle’s Law, also known as Mariotte’s Law or the Boyle-Mariotte Law, states that pressure and volume are inversely proportional as long as moles (n) and temperature (T) are held constant.
In a closed container, pressure represents the downward force applied to it while the volume represents the free space inside of it. According to Boyle’s Law, as the pressure on a container increases then the inside volume will decrease and vice-versa.
This opposing relationship can be illustrated by the following pressure-volume graph:
The inverse relationship between pressure and volume at a constant mass for a gas at a fixed temperature is illustrated by the expression:
Boyle’s Law Formula
The Ideal Gas Law is presented as:
If moles (n) and temperature (T) are held constant then the formula simplifies into:
In this form k represents our constant and when dealing with two sets of data for pressure and volume we obtain the Boyle’s Law Formula as:
Now let’s use it in a practice problem.
PRACTICE: A gas occupies 4.23 L at 2.25 atm. What is the volume at 3.46 atm?
STEP 1: Identify the variables given.
STEP 2: Isolate the missing variable for the second volume (V2).
Beyond Boyle’s Law
Boyle’s Law represents one of the Simple Gas Laws besides Charles Law, Avogadro’s Law and Gay-Lussac’s Law. In order to understand non-ideal gases we must examine the kinetic theory of gases and the Van der Waals equation.