A flask with a volume of 3.16 L contains 9.33 g of an unknown gas at 32.0°C and 1.00 atm. What is the molar mass of the gas? (R = 0.08206 L • atm/K • mol)
A) 7.76 g/mol
B) 66.1 g/mol
C) 73.9 g/mol
D) 81.4 g/mol
E) 144 g/mol

Question

Quizplus · Accepted Answer

We can use the ideal gas law to find the number of moles of the gas present:

PV = nRT

n = (PV)/(RT)

n = (1.00 atm)(3.16 L)/(0.08206 L・atm/K・mol)(305.15 K)
n = 0.1339 mol

We can then use the formula for molar mass:

M = m/n

M = 9.33 g/0.1339 mol

M = 69.6 g/mol

Therefore, the molar mass of the unknown gas is approximately 73.9 g/mol (rounded to one decimal place). The closest answer choice is C: 73.9 g/mol.

A Flask with a Volume of 3