Ideal Gas Law

Ideal Gas Law Equation

PV = nRT (Relates pressure, volume, moles, and temperature of a sample of gas).

Ideal Gas Law Variables

P = pressure in atm; V = volume in L; n = moles of gas; R = universal gas constant; T= temperature in Kelvin = Celsius + 273.15

Macroscopic Properties and Ideal Gas Law

The macroscopic properties of ideal gases (P, V, T, n) are related through the ideal gas law.

Graphical Representations

Graphical representations of the relationships between P, V, T, n are useful to describe gas behavior.

Boyles's Law (Relationship)

As gas pressure increases, gas volume decreases.

Boyles's Law (Formula)

P1V1 = P2V2

Charles's Law (Relationship)

As gas pressure increases, gas volume decreases

Charles's Law (Formula)

V1/T1 = V2/T2

Avogadro's Law (Relationship)

As the number of moles of a gas increases, gas volume increases (at constant P and T

Avogadro's Law (Formula)

V1/n1 = V2/n2

Dalton's Law of Partial Pressure

The total pressure of a mixture of ideal gases is the sum of the partial pressures exerted by each component.

Dalton's Law of Partial Pressure (Formula)

Ptotal = Pa + Pb + Pc + …

Partial Pressure (using Mole Fraction)

The partial pressure of a gas is equal to its mole fraction multiplied by the total pressure (Pa = Xa * Ptotal)

Mole Fraction ($\text{X}_{\text{A}}$)

The moles of component a divided by the total moles of gas Xa = moles A/total moles

Molar Mass (from Ideal Gas Law)

molar mass = (density (g/L) x R x Kelvin Temperature)/Pressure

Gases Collected Over Water

The total pressure in the container is the pressure of the collected dry gas plus the water vapor pressure (must subtract Pwatervapor from Ptotal)