Studying is a Gas!
Unit 3 Study Guide
ü Know the main points of the Kinetic Theory of Gases
ü Know what causes pressure…elastic collisions between gas particles and the container (if in a sealed
vessel)…more or less particles changes pressure: this can be helpful when answering questions about
reactions going to completion (comparing moles/particles of gaseous reactants versus
moles/particles of gaseous products)
ü Know what can cause pressure to increase (more particles, decreased container volume, increased
temperature/KE of particles) or decrease (less particles, increased container volume, decreased
temperature/KE of particles)
ü If gas particles get close enough together, intermolecular forces of attraction can cause them to
stay together…aka, become a liquid (liquefy). This can be accomplished through increased pressure,
decreased container volume and/or decreased temp, the same variables that make gases more dense
ü If temperature is held constant, the average kinetic energy stays the same!
ü Avogadro’s Law (1 mole of any gas at STP = 22.4 L) means different samples of gas at STP have the
same P, V, T, and number of particles (moles), but NOT mass/density!
ü Remember the difference between SPEED of gas particles and KE…Speed depends on size (mass –
effusion): particles can have different speeds with the same KE, as KE depends on mass and speed
(1/2mv2) and is measured as an average (temperature, on the Kelvin scale)
ü 100oC to 300oC is NOT an increase in temperature of a factor of 3! (100K to 300K is!)
ü A sample of gas doesn’t automatically weigh less than a liquid or solid…for example, when a substance
changes phase, its MASS does NOT change! (25 g of ice melts to become 25 g of water which vaporizes
to become 25 g of steam)
ü Gases deviate from Ideal behavior at lower temperatures and higher pressures; IMF’s lower the actual
pressure, and the volume of particles increases the actual pressure
ü Understand how to interpret the Maxwell-Boltzmann distribution curve for gases at different
temperatures
ü Know what information is given to you in your test taking packet so you are not unnecessarily
memorizing things: Ideal Gas Law (from which you can see Boyle’s, Charles’s, Gay-Lussac’s and the
Combined Gas Laws!); mole fraction (X) equation and how it relates to pressure of gases in a
nonreactive mixture as well as Dalton’s Law of Partial Pressure for nonreactive/inert gas mixtures;
conversion from Celsius to Kelvin; equation for KE; R constants for kPa (8.314), atm (0.08206) and
torr/mmHg (62.36); conversion between atm and torr/mmHg; STP conditions (273.15 K = 0°C); and
22.4 L/mol for an Ideal gas at STP
And be able to do these calculations:
Boyle’s Law
Charles’s Law
Avogadro’s Law
Combined Gas Law
PV=nRT
Find Molar Mass and Density of gases as
well as do Stoichiometry problems using
PV=nRT
Find mystery metal “M” like #5 on “R” lab