A 1.95 g sample of an unknown gas at 63 ∘ C and 1.10 atm is stored in a 1.75 L flask. What is the density of the gas?

Question

What is the molar mass of the gas?

Answer 1

Let us use the ideal gas law to find the number of moles of gas present.

PV = nRT

P = 1.10 atm

V = 1.75 L

R = 0.0821 Latm/Kmol

T = 63 + 273 = 336K

n = moles = PV/RT

n = (1.10 atm)(1.75 L)/(0.0821 Latm/Kmol)(336K)

n = 0.06978 moles

molar mass = 1.95 g/0.06978 moles = 27.9

density of gas = 1.95 g/1.75 L = 1.11 g/L