1. Warm Up: “More Combined Gas Law Questions”
Today: Ideal Gas Law
Learning Targets:
I can use the combined gas law to calculate the effects of changing variables of gases.
I can use the ideal gas law to make predictions about an ideal gas scenario.
Homework: None

2. More Combined Gas Law Practice
A gas occupies a volume of L. The original temperature was cooled to 7.71 ºC and the resulting volume was L. What was the original temperature of the gas?
An aerosol can has a pressure of 3.2 atm of compressed difluoroethane gas. The can begins at room temperature (298K) and is chilled until the pressure reads 2.4 atm . What is the new temperature of the gas in the can?
500.0 mL of hydrogen at 20.0ºC and 121 kPa changed to STP. What is the new volume of the gas?

3. The Ideal Gas Law

4. Three Assumptions about Gases
assume
ideal
We that we live in an world where:
Gases move randomly in linear paths
The distance between molecules is very large (gases take up a much larger volume than the size of their atoms)
Gases undergo elastic collisions – ignore any intermolecular forces that would stick gases together when they collide

5. Real Gases vs. Ideal Gases
Gases are assumed to behave ideally under normal conditions
The behavior of gases deviates from ideal under:
HIGH pressures (gas molecules pushed closer together… more likely to feel intermolecular forces)
LOW temperatures (gas molecules move very slowly and can condense into liquid if they stick together… intermolecular forces!)

6. Why are these assumptions important?
PV = nRT
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7. PV = nRT P V n R T The Ideal Gas Law RESSURE OLUME MOLES GAS CONSTANT
EMPERATURE
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8. The MysteRious R
R is a constant that is determined from the state of gases at STP.
At STP: 1 mole of a gas takes up 22.4 L
PV = nRT
R = PV
(1 atm)(22.4L) =
= atm · L nT
mol · K
(1 mol)(273K)
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9. Ideal Gas Law Problems PV = nRT V = nRT P V = 49.8 L V =
1.007 atm
2.05 mols of a gas are stored at 102 kPa at
25.0ºC. What is the volume this gas takes up?
PV = nRT
V = nRT P
V =
(2.05 mols)( atm · L)(298 K)
(1.007 atm)(mol · K)
V = 49.8 L

10. Ideal Gas Law Problems PV = nRT P = nRT V P = 4.9 atm P =
1.00 moles of a gas is stored in a 5.0 L
container at a temperature of 298 K. What is
the pressure of the gas?
PV = nRT
P = nRT V
P =
(1.00 mols) atm· L)(298 K)
(5.0 L)(mol · K)
P = 4.9 atm

11. Ideal Gas Law Problems PV = nRT n = PV RT 1.55 mol n =
Nitrogen gas is stored at a pressure of
523kPa in a container that is 6.3 L big at
255 K. How many grams of nitrogen are in
the container?
5.16 atm
PV = nRT
n = PV RT
1.55 mol
n =
(5.16 atm)(mol · K)(6.3L) =
( atm · L)(255 K)
1.55 mol N2
28.02 g N2 x
= g N2
1 mol N2