Ch' 11 Molecular Composition of Gases

1
Ch. 11 Molecular Composition of Gases

• If the volume of a gas in the product and
  reactant of a chemical equation is left at a
  constant temp. and pressure, then it can be shown
  as a ration.
• Avogadros principle says that equal volumes of
  gases at the same temp. and pressure contain
  equal numbers of molecules.

2

• V kn
• Volume constant x number of moles
• The volume of a gas is directly proportional to
  the number of moles of a gas. (At a constant
  temp. and pressure)
• Each gas will occupy the same volume at the same
  temp. and pressure ? Avogadros principle.
• Standard molar volume of a gas is the volume
  occupied by 1 mole of a gas at STP? 22.4 L

3

• The molar mass of a gas 1 mol. of a gas 22.4
  L of a gas at STP.
• Sample Problem 11-1
• Sample Problem 11-2
• Ideal Gas Constant ? R PV/nT
• Ideal gas law relation between temp., pressure,
  volume, and of moles of a gas.
• Sample Problems 11-3 to 11-5
• Mass / molar mass of moles
• PV mRT/M

4

• PV nRT or PV mRT/M
• Sample Problem 11-6
• Density mass / volume
• P mRT/VM
• D MP / RT

5
Stoichiometry of Gases

• 1. Volume to Volume
• Volume A ? Volume B
• Volume A x mol. B / mol. A VOLUME B
• Sample Problem 11-7

6

• 2. Volume to Mass
• Volume A ? Mol. A ? Mol. B ? mass B
• USE n PV / RT to convert volume to mass
• Mol. A x mol. B / mol. A mol. B x molar
  mass B MASS B
• Sample Problem 11-8

7

• 3. Mass to Volume
• Mass A ? Mol. A ? Mol. B ? Volume B
• Mass A / Molar mass A x mol. B / mol. A
  mol. of B
• Use V nRT/P to covert mol. of B into volume of
  B
• Sample Problem 11-9