Stoichiometry problem?

Just to do it quicker: R is a constant and in this case n doesn't change. So you can just use the equation P1V1/T1 = P2V2/T2, where P1, V1, T1 - numbers from the first experiment, P2, V2, T2 - from the second. as far as it is the ratio, here it doesn't matter, in which units will you input the values, they just have to be the same on the two sides. The answer still is 16L ;)