1. Every element has an atomic mass
Hydrogen
Oxygen
Carbon
Sodium
………
Every element has an atomic mass
Measured in
atomic mass units (u)
(1 u = x kg)

2. Molecules – combinations of atoms
2 Hydrogens
Every element has an atomic mass
Which is Measured in
atomic mass units (u)
(1 u = x kg)
1 Oxygen
Molecules – combinations of atoms
Molecular mass = 2 (mH) + 1 (mO)
= 2 ( u) + 1 ( u)
= u
Objects contain billions of particles
1 mole of particles = x 1023 particles = NA
Avogadro’s Number
(The SI unit for quantity of a substance)

3. A mole (mol) is defined as the number of grams of a substance that is numerically equal to the molecular mass of the substance:
1 mol H2 has a mass of 2 g
1 mol Ne has a mass of 20 g
1 mol CO2 has a mass of 44 g
The number of moles in a certain mass of material:
The number of moles in a certain number of particles:

4. k = Boltzmann’s Constant = 1.38 x 10-23 J/K = R/NA
The Ideal Gas Law
PV=nRT
P = Pressure (Pa)
V = Volume (m3)
n = # of moles (mol)
R = 8.31 J/mol K
= (L.atm)/(mol.K)
If N = # of particles
T = Temp. (K)
PV=NkBT
k = Boltzmann’s Constant = 1.38 x J/K = R/NA
Web Link: Ideal Gas

5. PV=nRT PV=nRT Ideal Gas at Constant Temperature (Isothermal)
PV=constant
Boyle’s Law
constant
PiVi= PfVf or
Ideal Gas at Constant Pressure
Charles’ Law
PV=nRT
constant or

6. A gas is contained in an 8.0 x 10-3 m3 vessel at 20 °C
and a pressure of 9.0 x 105 N/m2.
(a) Determine the number of moles of gas in the vessel.
A gas is contained in an 8.0 x 10-3 m3 vessel at 20 °C
and a pressure of 9.0 x 105 N/m2.
(b) How many molecules are in the vessel?

7. A cylinder with a moveable piston contains gas at a temperature of 27 oC, a volume of 1.5 m3, and an absolute pressure of 0.20 x 105 Pa.
What will be its final temperature if the gas is compressed to 0.70 m3 and the absolute pressure increases to 0.80 x 105 Pa?
1.5 m3
27 oC
0.20 x 105 Pa
0.70 m3
0.80 x 105 Pa