1. The Ideal Gas Law

2. Real Gas Behaviour
There are several assumptions in the kinetic molecular theory that describe an ideal gas
Gas molecules have zero volume
Forces of attraction/repulsion are zero
Molecules move in straight lines
Collisions are completely elastic
However, at high pressure and low temperature there are problems with these assumptions
In very small volumes there will be many more interactions and collisions
The volumes of the gas molecules is now a significant fraction of the container

3. Real Gas
Ideal Gas
In some cases (polar molecules), mild attractions exist between particles (volume is mildly decreased)
No attractions exist between particles (no IMF)
Gas particles occupy space
Gas particles have no volume
Some gases do condense at low temperature and high pressure
Ideal gases will NOT condense into liquid
“Mostly” obey the gas laws
Obey gas laws perfectly
Constant RANDOM motion
Motion of particles is always in straight lines

4. The Ideal Gas Law Boyle’s Law: PV = k or V = k P
Charles’ Law: V = k or V = aT T
Avogadro’s Law: V = b or V = bn n
V = kab X nT
V = RnT or PV = nRT

5. PV= nRT Unit Analysis! P = pressure (kPa) V = volume (L) PV = nRT
R = PV nT
R = (kPa)(L)
(mol)(T)
R = kPa·L/mol·K
P = pressure (kPa)
V = volume (L)
n = amount (mol)
T = temperature (K)
R = ??

6. Try These…
Use the ideal gas law to calculate the molar volume of a gas at SATP.
A cylinder of laughing gas (N2O) has a diameter of 23.0 cm and a height of 140 cm. The pressure is 108 kPa at a temperature of 294 K. How many grams of laughing gas are in the cylinder?
Hint: Vcylylinder = r2h

7. Homework
Read p
P. 445 #3,4,6
P. 448 #1-6