Chem
posted by B .
A chemist was asked to find the molecular mass of a gas. She massed the gas and found that 3.73 g of the gas occupied 300 cm3 at 25°C and 92.4 kPa. What is the molecular weight of the gas?

PV=nRT
solve for n. Now knowing the number of moles, you know the mass of n moles, so you can get the mol mass. 
Use PV = nRT to calculate n = number of mols.
Then use mols = g/molar mass to calculate molar mass. Post your work if you get stuck.