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

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