Unit 7 Gas Laws

Gases Gases (g): Transparent, compressible, expand without limit, have no shape/volume. **Take the shape and volume of their container.

Gases exert pressure: STP: defined as standard temperature and pressure *Found on Table A 1atm 101.3kPa *Pressure can also be 760 torr or 760 mm Hg

Kinetic Molecular Theory of Gases Ideal Gas Laws Ideal gases are those whose gas particles (molecules): travel in random, constant, straight line motion. (*At absolute zero, all kinetic energy ceases, so all particles stop moving.)

are separated by great distances relative to the size of the molecule so that the volume of the actual molecule is considered negligible.

have no real attractive forces between them. have collisions that may result in the transfer of energy between particles {but remember overall energy is conserved} ENERGY

Real Gases Real gases do have volumes and do exhibit attractive forces between their particles or we would have no atmosphere!

For real gases to behave like ideal gases: Temperature must be high Pressure must be low The two most common real gases that behave most like ideal gases are H 2 and He because they are the smallest and least dense

Avagadro’s Hypothesis under the same conditions of temperature and pressure, 2 equal volumes of two different gases will have the same number of particles regardless of their masses. At STP, this number of particles is Avogadro’s number, which is 6.02 x 10 23

The Combined Gas Law The pressure a gas exerts on its surroundings is related to its temperature and volume such that: FORMULA: P 1 V 1 = P 2 V 2 T 1 T 2 *note* Temperature must be in KELVIN!!! Pressure 1 and 2 and Volume 1 and 2 must be in the same units. See examples

Boyle’s Law As long as temperature remains constant, pressure and volume of a gas will affect each other inversely FORMULA: P 1 V 1 = P 2 V 2 See example

Charles Law  As long as the pressure on a given mass of a gas remains constant, the temperature and volume will affect each other directly.  FORMULA: V 1 = V 2 T 1 T 2  See example Temp Vol

Gay-Lussac’s Law As song as the volume of a given mass of a gas remains constant, the temperature and pressure will affect each other directly.  FORMULA: P 1 = P 2 T 1 T 2 To graph this relationship: Pressure Temp