posted by Lena .
I need to find the mass of butane gas and I only know the following things (you cannot use the molar mass of butane):
volume = 80 mL
pressure = 98.23 KPa
So I found the number of mols and I got 0.003171814 mols. of butane.
But I don't know what to do after this since I can't use molar mass.
Use PV = nRT to get the number of moles, n. You already did that.
You need the molar mass to get the mass of butane. Any ideal gas with that P, V and T will have the same number of moles.
More facts are needed or the question cannot be answered