Question

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
temp.= 298K

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.

Answer 1

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