1

Graham’s Law• Gases expand to occupy the volume that is available to it.• This is Diffusion – movement from _____ concentration to

_______ concentration.• Diffusion occurs a different rates depending on the ______ of

the gas.– T and P are _______– A denser (“heavier”) gas diffuses ____ ______.– A less dense (“lighter”) gas diffuses _______.

H2 = 2g/1 mol HCl = 36.45g/1 mol N2 = 28g/1 mol

H2O = 18g/1 mol CH4 = 44g/1 mol

2

Combined Gas Law

• Relates Temperature, Volume, and Pressure of a gas• Combination of all 3 previous gas laws• ___________________________________________• FORMULA:

P1V1 = P2V2

T1 T2

(2)(20) = (4) V2 500 200

Cross multiply 2000 V2 = 8000 2000 V2 = 8000 2000 2000

V2 = 4L

(2.7)(14) = (5) (9) 345 T2

15525= 37.8 T2 T2 = 410.7 K

3

Determining Density of a Gas

• D = m/V• For 1 mole of a substance– D = formula mass/ molar volume– Molar volume = 22.4 L

Assume 1 mol of gas

Assume 1 mol of gas

D = m v

D = 44g (in 1 mole) 22.4 L (in 1 mole)

D = 1.96 g/L

D = m v

0.8 = m 22.4

m = 17.92 g ( in 1 mole)So formula mass is 17.92 g/mol

4

PV = nRTP(5.6) = (2)(0.082)(283)P = 8.29 atm

PV = nRT(1)V = (3)(0.082)(273)V = 67.16 L