The Gas Laws

Units- are used to identify each variable

• Volume- mL, L, cm3

• Temperature- if given in °C convert to

Kelvin- K

• Pressure- atm, torr, mmHg, psi (lbs/in2), kPa

Boyle’s LawPressure –Volume relationship

•For a given mass of gas, at constant temperature, the volume of the gas varies inversely with pressure.

IF PRESSURE INCREASES VOLUME___________

IF PRESSURE DECREASES VOLUME___________Equation:

P1 x V1 = P2 x V2

•Subscript 1 represents starting conditions.•Subscript 2 represents final conditions.•P= Pressure•V= Volume•Temperature is NOT included because it remains constant

Why would the temperature have to remain constant?

Boyle’s Law Example

A gas with a volume of 4L at a pressure of 90 kPa is allowed toexpand until the pressure drops to 20 kPa. What is the new volume?

Step 1: Determine values

P1=

V1=

P2=

V2=

Step 2:

Plug into equation

Step 3:

Solve for unknown

Step 4:

Check work

Charles’ LawVolume- temperature relationship

•For a given mass of gas, the volume of the gas is directly proportional

to its Kelvin temperature if pressure is held constant.

Temperature is always in Kelvin.10 °C + 273= 283 K25 °C + 273= 298K

Equation:V1 = V2

T1 T2

Charles’ Law Example

• A balloon at 27 °C has a volume of 4.0 L. The balloon is heated to 57 °C. What is the new volume?

Step 1: Determine values

V1=

T1=

V2=

T2=

Step 2:

Plug into equation

Step 3:

Solve for unknown

Step 4:

Check work

Gay-Lussac’s LawPressure –Temperature relationship

•For a given mass of gas, the pressure is directly proportional to its

Kelvin temperature if volume is held constant.

Equation:P1 = P2

T1 T2

http://www.marymount.k12.ny.us/marynet/06stwbwrk/06gas/1amcslussac/amcsgaylussac.html

Gay-Lussac’s Example

Step 1: Determine values

P1=

T1=

P2=

T2=

Step 2:

Plug into equation

Step 3:

Solve for unknown

Step 4:

Check work

A sample of gas in a rigid container at 10 °C is at a pressure of 800 torr. What temperature will be necessary to change the pressure to 1100 torr?