Every element has an atomic mass Hydrogen Oxygen Carbon Sodium ……… Every element has an atomic mass Measured in atomic mass units (u) (1 u = 1.6605 x 10-27 kg)

Molecules – combinations of atoms 2 Hydrogens Every element has an atomic mass Which is Measured in atomic mass units (u) (1 u = 1.6605 x 10-27 kg) 1 Oxygen Molecules – combinations of atoms Molecular mass = 2 (mH) + 1 (mO) = 2 (1.00794 u) + 1 (15.9994 u) = 18.0153 u Objects contain billions of particles 1 mole of particles = 6.022 x 1023 particles = NA Avogadro’s Number (The SI unit for quantity of a substance)

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:

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 = 0.0821 (L.atm)/(mol.K) If N = # of particles T = Temp. (K) PV=NkBT k = Boltzmann’s Constant = 1.38 x 10-23 J/K = R/NA Web Link: Ideal Gas

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

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?

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