1. Boyle’s Law
Pressure and Volume

2. Background
The first careful experiments on gasses were performed by Robert Boyle (1600s)
Boyle studied the relationship between the pressure of a trapped gas and its volume
Boyle’s Observations:
As the pressure increases, the volume of trapped gas decreases
P = Pressure
V = Volume
k = a constant at a specific temperature for a given amount of gas
PV = k

3. Boyle’s Law
Boyle observed that as pressure increases, volume decreases, and vice versa
The relationship is proportional
If we know the volume of a gas at a given pressure, we can predict the change in volume if the pressure is changed
P1V1 = k
and
P2V2 = k
we can say: P1V1 = k = P2V2
Or just: P1V1 = P2V2

4. Calculating Volume
A 1.5-L sample of gaseous CCl2F2 is contained at a pressure of 56 torr. If the pressure is changed to 150 torr at a constant temperature,
Will the volume of the gas increase or decrease?
What will be the new volume of the gas?
Step 1: write down the information given:
P1 = 56 torr P2 = 150 torr
V1 = 1.5 L V2 = ?
Step 2: use Boyle’s law to solve:
(56)(1.5)= (150)(V2)
V2 = (56)(1.5)
150
V2 = 0.56 L

5. Calculating Pressure
In a car engine the gaseous fuel-air mixture enters the cylinder and is compressed by a moving piston before it is ignited. In a certain engine the initial cylinder volume is L. After the piston moves up, the volume is L. The mixture initially has a pressure of 1.00 atm. Calculate the pressure of the compressed mixture.
Step 1: write down the information given:
P1 = 1.00 atm P2 = ?
V1 = L V2 = L
Step 2: use Boyle’s law to solve:
(1.00)(0.725)= (P2 )(0.075)
P2 = (1.00)(0.725)
0.075
P2 = 9.7 atm

6. Boyle’s Law Practice Problems:
Calculate the missing quantity:
V = 249mL at 764 mm Hg; V = ? At 654 mm Hg
V = 1.04 L at 1.21 atm; V = ? At atm
V = 525 mL at 1.09 atm; V = 122 mL at ? Atm
V = 2.79 mL at 20.2 atm; V = 209 mL at ? Atm
V = 52.1 L at 755 mm Hg; V = ? At 761 mm Hg
What pressure would be needed to compress 25.1 mL of Hydrogen at 1.01 atm to 25% of its original volume?
If the pressure on a 1.04-L sample of gas is doubled, what will be the new volume of the gas?
A 1.04-L sample of gas at 759 mm Hg pressure is expanded until its volume is 2.24 L, what will the pressure be in the expanded gas sample be?