# What is the mass of a gas that occupies 48.9 liters, has a pressure of 724 torr, a temperature of 25°,C and a molecular weight of 345 g?

May 24, 2014

For this question, we're going to start with the Ideal Gas Law

$P V = n R T$

We know $n$ is the number of moles of the gas, which we can find by taking the mass of the gas ($m$) and dividing it by the molecular weight ($M$). Substituting this in we get:

$P V = \frac{m R T}{M}$

Solving this for $m$:

$m = \frac{P V M}{R T}$

Looking up the value for R with our units, gives us a value of 62.36367.

Plug in our numbers (Remember to convert Celsius to Kelvin and solve to get an answer of approximately 657g.