At standard pressure and 373 K,a 0.333-g sample of an unknown pure gas occupies a volume of 0.255 L.What is the identity of the gas?
A)xenon
B)argon
C)neon
D)helium
E)krypton

Question

Quizplus · Accepted Answer

Using the ideal gas law, $PV = nRT$, where $P$ is the pressure (1 atm for standard pressure), $V$ is the volume (0.255 L), $n$ is the number of moles, $R$ is the ideal gas constant (0.0821 L·atm/(mol·K)), and $T$ is the temperature (373 K). First, solve for $n$: $n = \frac{PV}{RT}$. Substituting the given values, $n = \frac{(1)(0.255)}{(0.0821)(373)}$, which gives $n \approx 0.00827$ moles. The molar mass of the gas is then $M = \frac{mass}{n} = \frac{0.333g}{0.00827mol} \approx 40.3$ g/mol. Argon has a molar mass of approximately 40 g/mol, making it the correct answer.

At Standard Pressure and 373 K,a 0