Ideal Gas Law

Ideal Gas

Imaginary gas that conforms to all of the assumptions of the kinetic molecular theory (Day 1)

Real Gas

Can sometimes conform to all of the assumptions of the kinetic theory it can behave ideally

Does not behave ideally at high pressures and/or low temperatures

Ideal Gas Law

P = pressureV = Volume (L) n = number of moles R = ideal gas constantT = temperature (K)

P V = n R T

R: Ideal Gas Constant

R = 0.0821 L atm K mol

R = 62.4 L mmHg K mol

Choose R so that the pressure units match the pressure units in the

problem.

Example #1:

What is the pressure (in mm Hg) exerted by 85.5 g of CO2 at 27˚C if the gas is contained in a 15.0 L container?

P = ?

V = 15.0 L

n = ? (85.5 g)

R = 62.4 62.4 L mm HgL mm Hg

K molK mol

T = 27oC + 273 = 300 K

Example #1:

PV = nRTP = nRT

V

Example #2:What is the mass of 120 L of SO2 at a

temperature of 40˚C and a pressure of 1.85 atm?

P = 1.85 atm

V = 120 L

n = ??? (but want grams)

R = 0.0821 L atm

K mol

T = 40oC + 273 = 313 K

Example #2:

PV = nRT

n = PVRT

We can also derive many formulas from PV=nRT to determine other values…Molar Mass = DRT

PMolar Mass = # grams

# moles (n)

Density = P*Molar Mass

RT

Example 3What is the molar mass of a gas if 0.628g of the gas occupies a volume or 150 mL at 25˚C and 7456 mm Hg pressure?

Molar Mass = # g 0.628 g

# mol

Use PV=nRT to find the moles:

n = PV

RT