What volume of sulfur trioxide would be produced by reaction of 2.56 L of oxygen with excess sulfur at STP?

The balanced chemical reaction would be:

S + O2 = SO2

2SO2 + O2 = 2SO3

We are given the amount of oxygen to be used in the reaction. This will be the starting value in the calculations. We do as follows:

2.56 L O2 (1 mol / 22.4 L) (1 mol SO2 / 1 mol O2) (2 mol SO3 / 2 mol SO2) 22.4 L / 1 mol = 2.56 mol SO3