Determine the number of moles of sulfur trioxide produced when 3.5 moles of oxygen gas is consumed in the reaction

The balanced chemical reaction would be:

2SO2 + O2 = 2SO3

We are given the amount of oxygen to be used. We calculate as follows:

3.5 moles O2 ( 2 mol SO3 / 1 mol O2 ) = 7 mol SO3 is produced from the reaction. 

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