What is the molar mass of an unknown gas if 0.948 g of the gas occupies a 2.50 L vessel and its temperature and pressure were measured and found to be 65°C and 250. torr, respectively?

Answer 1

Ideal gas law:

PV = nRT

P = pressure = 250. torr

V = volume = 2.50 L

n = moles = ?

R = gas constant = 62.36 L-torr/Kmol (note to use the proper gas constant have torr as units)

T = temperature in K = 65 + 273 = 338K

Solving for n, we have...

n = moles = PV/RT = (250.torr)(2.50 L) / (62.36 Ltorr/Kmol)(338K)

n = 0.02965 moles

Molar mass = gram/moles = 0.948 g / 0.02965 moles

Molar mass = 31.97g/mol = 32.0 g/mol