Chem - Ch 5

4 Properties of Gases

4 Properties of Gases

• They fill any container

• Easily compressed

• Mix completely w/ other gases

• Exert pressure

Boyle’s Law

Pressure is inversely related to volume

Four variables that impact gases

Pressure, volume, moles, and temperature

Charles’s Law

Volume is directly related to temperature

Avogadro’s Law

Volume is directly related to moles

Ideal Gas Law

PV=nRT

STP

Standard temp and pressure ( 273 degrees K and 1 atm)

Combined Gas Law

P1V1/n1T1 = P2V2/n2t2

Formula for molar mass

grams/mols

Formula for density

m/v

Formula for density in terms of PV=nRT

P/RT = n/V

Gay-Lussac’s Law

The volume of any two gases in a reaction at constant temp/press is equal to the mol ratios

Partial Pressure Equation

naRT/V + nbRT/V = Ptotal

Mole Fractions

mol a/total mol x Ptotal = Pa

Kinetic Molecular Theory

Gases are made of small particles in constant motion. The collision of these particles with the walls causes pressure. Kinetic energy is directly related to temperature. As temp increases, speed increases, collisions increase, and pressure increases.

Formula for speed

U = (3RT/M)^1/2

Graham’s Law

Smaller particles effuse faster

Effusion

The flow of gas particles through a small hole

Units for speed

mols/seconds

Formula for effusion

Ub/Ua = (MMa/MMb)^1/2

Non-Ideal conditions

High pressure and low temps

What happens at low temperatures that makes PV = nRT not work?

The particles slow down and attractive forces take over.

What happens at high pressures that makes PV = nRT not work?

The particles are pushed together and attractive forces take over. At very high pressures, the size of the particles prevent the volume from getting any smaller.