Chemistry 103 Help

Question

A 3.45 g sample of an unknown gas at 45 ∘C and 1.05 atm is stored in a 1.45 L flask.

What is the density of the gas?

What is the molar mass of the gas?

molar mass:

Answer 1

Density is mass / volume. Molar mass is mass / moles. We know the mass (3.45 g), and the volume (1.45 L) so we need to find the moles in order to find the molar mass.

Density = mass/volume = 3.45 g / 1.45 L = 2.38 g/L

Find moles using ideal gas law

PV = nRT

n = moles = PV/RT

n = (1.05 atm)(1.45 L) / (0.0821 Latm/Kmol)(318K)

n = 0.0583 moles

molar mass = 3.45 g / 0.0583 mols

molar mass = 59.2 g/mol