1. DO NOW: Complete on the BACK of the HW WS!
A gas has a pressure of 0.12 atm at 21.0 °C. What is the pressure at standard temperature?
2. If I have 5.6 L of gas in a piston at a pressure of atm and compress the gas until its volume is L, what will the new pressure inside the piston be?
3. If I have 45 liters of helium in a balloon at 250 C and increase the temperature of the balloon to C, what will the new volume of the balloon be?

2. Notes
Unit: Gas Laws
Combined Gas Law

3. After today you will be able to…
Explain the effect on gas properties using the Combined Gas Law
Calculate an unknown pressure, temperature, or volume by solving algebraically

4. The Combined Gas Law
The combined gas law is a single expression that combines Boyle’s, Charles’s, and Gay-Lussac’s Laws.
This gas law describes the relationship between temperature, pressure, and volume of a gas.
It allows you to do calculations where only the amount of gas is constant.
RB + JC + JG-L = BFFs!

5. P1V1 P2V2 T1 T2 = The Combined Gas Law
Helpful hint: You are able to get which law you need by covering the variable that is not mentioned in the problem! There is no need to memorize 4 individual laws, just memorize the Combined Gas Law and you can derive all of the others!
If there is no mention of pressure in the problem, cover P up and you are left with the relationship between T and V. (aka Charles’s Law!)
If there is no mention of volume in the problem, cover V up and you are left with the relationship between T and P. (aka Gay-Lussac’s Law!)
For example, if there is no mention of temperature in the problem, cover T up and you are left with the relationship between P and V. (aka Boyle’s Law!)
P1V1 P2V2
T T2 =

6. The Combined Gas Law P1 V1 P2 V2 = T1 T2 P2 467mmHg = P1= V1= T1= P2=
A gas occupies 3.78L at 529mmHg and 17.2°C. At what pressure would the volume of the gas be 4.54L if the temperature is increased to 34.8°C?
P1=
V1=
T1=
P2=
V2=
T2=
P1 V1 P2 V2
T T2 =
529mmHg
3.78L
17.2°C + 273= 290.2K
(529mmHg)
(3.78L)
(P2)
(4.54L) ? =
(290.2K)
(307.8K)
4.54L
467mmHg
34.8°C + 273= 307.8K P2 =

7. Questions? Complete WS