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.
Boyle’s Law
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.
Inversion Relationship of Pressure & Volume
This opposing relationship can be illustrated by the following pressure-volume graph:
PV 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 Expression
Boyle’s Law Formula
The Ideal Gas Law is presented as:
Ideal Gas Law
If moles (n) and temperature (T) are held constant then the formula simplifies into:
Ideal Gas Law (Simplified)
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:
Boyle's Law Formula
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.
Identifying given variables (Boyle's Law)
STEP 2: Isolate the missing variable for the second volume (V2).
Solving missing variable (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.
