This law states that if a pressure of a gas is increased, the volume of the gas is decreased. Study the following figures.
This law can be mathematically expressed as:
P1V1=P2V2
where:
- P1 = initial pressure
- V1 = initial volume
- P2 = final pressure
- V2 = final volume
Any units of pressure and volume may be used. However, uniformity must be observed.
Pressure Units
- 1 atmosphere (atm) = 760mm Hg = 760 torr = 150000 Pascal (Pa)
Volume Units
- 1 Liter = 1000 mL
- 1mL = 1 cm3
Problem Solving Reminders:
- Analyze the given problem.
- List down the given values and what is asked.
- Identify the formula to be used.
- Write solutions clearly.
- Analyze if you have the correct answer.
Sample Problem #1:
Two hundred milliliter of gas is contained in a vessel under a pressure of 850mm Hg. What would be the new volume of the gas if the pressure is changed to 1000mm Hg?
Given:
P1= 850 mm Hg
V1= 200 cm3
P2= 1000 mm Hg
V2= ?
Equation: P1V1 = P2V2- Solution:
P1V1 = P2V2
(850mm Hg)(200cm3)=(1000mm Hg) V2
(850mm Hg)(200cm3)= V2
(1000mm Hg)
170 cm3 = V2
Sample Problem #2:
A 2.5 liter sample of a gas is collected at a pressure of 1.25 atm. Calculate the pressure needed to reduce the volume of a gas to 2.0 liters. The temperature remains unchanged.
- Given:
P1= 1.25 atm
V1= 2.5 liter
P2= ?
V2= 2.0 liters
Equation: P1V1 = P2V2
Solution:
P1V1 = P2V2
(1.25 atm)(2.50 L) = P2 (2.0 L)
(1.25 atm)(2.50 L) = P2
(2.0L)
P2 = 1.56 atm
