A 0.333-g sample of an unknown pure gas occupies a volume of 0.255 L at a pressure of 1.00 atm and a temperature of 100.0 °C. The unknown gas is ________.
A)xenon
B)neon
C)krypton
D)helium
E)argon

Question

Quizplus · Accepted Answer

Using the ideal gas law, PV = nRT, we can calculate the molar mass of the gas. First, convert the temperature to Kelvin (100.0 °C = 373.15 K). The ideal gas constant R is 0.0821 L·atm/mol·K. Solving for n (moles of gas), n = PV/RT = (1.00 atm)(0.255 L) / (0.0821 L·atm/mol·K)(373.15 K) = 0.00834 mol. The molar mass is then mass/n = 0.333 g / 0.00834 mol = 39.9 g/mol, which corresponds to argon.

A 0333-G Sample of an Unknown Pure Gas Occupies a Volume