Gas Laws

Avogadro's Law. The Ideal Gas Law. P V = n R T. P1 V1 n1 T1. = P2 V2 n2 T2. If pressure and moles do not change in the problem, omit those variables. ...

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A. Romero 2010

Gas Laws CHEM 1A Boyle’s Law

Charles’s Law

Gay-Lussac’s Law

The Combined Gas Law

Avogadro’s Law

P1 V1 = P2 V2

V1 V = 2 T1 T2

P1 P = 2 T1 T2

P1 V1 P V = 2 2 T1 T2

V1 V2 = n1 n2

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

Root Mean Squared Velocity 3RT M

urms =

MB MA

R = 8.31451 J/K∙mol M = molar mass in kg/mol

* indicate the specific type of rate (Velocity, Rate diff., or Rate eff.)

Dalton’s Law of Partial Pressures

The Ideal Gas Law

Mole Fraction

PV= nRT

nA PA A = = ntotal Ptotal

a = van der Waals constant b = van der Waals constant A = mole fraction of A d = density M = molar mass n = # of moles P = pressure PA = partial pressure gas A R = 0.08206 L·atm/K·mol T = temperature V = volume STP = 0ºC & 1 atm

Ptotal = PA + PB + PC …

At STP: 1 mole = 22.4 L 1 atm ≡ 760 torr

dRT M = P

K = °C + 273.15 Important Rules for Units  T always in Kelvin  P1 & P2 units match  V1 & V2 units match  All P units in Dalton’s Law match  All units match those of R in the Ideal Gas Law

van der Waals Equation n Pobs + a V

2 V–nb = nRT

Atm · L2 mol2

L mol

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