Apr 8th 2017, 03:42 PM
Join Date: Apr 2015
Location: Somerset, England
I don't think this is right at all.
There are several ways to do this but none involved switching to the molar equation.
Where did the question tell you the molar mass of air?
The density was given because it tells you how much is in a given volume, but at a different temperature and pressure from the one the gas is at.
So you must either correct this density to the new temperature and pressure or reduce the given values to STP.
Then you can use the information to obtain the mass of gas.
P1V1/T1 = P2V2/T2
Since you are given P1, P2, T1 and T2 you can correct 20 litres of gas at 4 atm and 17C to V2 litres of gas at STP and multiply by the given density.in kg/litre