Gas Laws

Gas Laws. CHEM 30A. Note: Many of the gas laws can be found by solving the Ideal Gas Law for R, and then omitting any variables that do not change. Ex...

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A. Romero 2007

Gas Laws CHEM 30A Boyle’s Law

Charles’s Law

Gay-Lussac’s Law

The Combined Gas Law

P1 V1 = P2 V2

V1 V2 = T1 T2

P1 P = 2 T1 T2

P1 V1 P V = 2 2 T1 T2

Avogadro’s Law V1 V = 2 n1 n2

Dalton’s Law of Partial Pressures Ptotal = PA + PB + PC …

The Ideal Gas Law PV= nRT M =

Graham’s Law of Effusion (for relative velocities or rates of diffusion/effusion) Rate Gas A = Rate Gas B

STP = 0ºC & 1 atm At STP: 1 mole = 22.4 L

MB

1 atm ≡ 760 torr

MA

K = °C + 273.15

    

Important Rules for Units

dRT P

P = pressure V = volume n = # of moles R = 0.08206 L·atm/K·mol T = temperature M = molar mass d = density

T must always be in Kelvin P units for conditions 1 & 2 must match V units for conditions 1 & 2 must match All P units in Dalton’s Law must match All units must match those of R in the Ideal Gas Law

Note: Many of the gas laws can be found by solving the Ideal Gas Law for R, and then omitting any variables that do not change. Example:

The Ideal Gas Law

P1 V1 P V = 2 2 n1 T1 n2 T2

PV= nRT R =

PV nT

If pressure and moles do not change in the problem, omit those variables Charles’s Law V1 V2 = T1 T2