Unit 7: Gas Laws

Boyle’s Law

CP Chemistry

Boyle’s Law

At constant temperature, the volume of a given amount of gas varies inversely with the pressure.

P1V1 = P2V2 (Temp. and gas particles are constant)

Pressure and Volume units must be the same on both sides of the equation!

Pressure vs Volume y = 7.5565x-0.9041

R2 = 0.9997

0

0.5

1

1.5

2

0 5 10 15 20 25

Volume (mL)

Pressu

re (

atm

)

Pressure vs Volume y = 8.3329x + 0.0994

R2 = 0.9986

0

0.5

1

1.5

2

0 0.05 0.1 0.15 0.2 0.25

Volume (1/mL)

Pressu

re (

atm

)Boyle’s Law Graph

Pressure vs. 1/volume Slope = P

1/V

PV = Constant

Problem #1

A sample of helium gas in a balloon is compressed from 4.0L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0L volume is 2 atm, what will the pressure be at 2.5L? P1V1 = P2V2

P1= 2atm P2= ? V1= 4.0L V2= 2.5L

(2atm)(4.0L) = (P2)(2.5L)

P2 = 3.2 atm(2atm)(4.0L) = P2

(2.5L)

Sample Problem #2A sample of carbon dioxide gas in a container is

compressed at a constant temperature. If the initial volume is 560mls and the pressure of the gas changes from 830torr to 1250 torr, what will the new volume be?

P1V1 = P2V2

P1= 830 torr P2= 1250 Torr V1= 560mL V2= ? mLs

(830torr)(560mL) = (1250torr)(V2)

V2 = (830torr)(560mL) (1250Torr)

V2 = 372 mLs

Boyle’s Law Video

Gas Properties link for take home lab

http://phet.colorado.edu/simulations/