2S+3O2=2SO3 is the equation... what mass of molecular oxygen when reacted with excess sulfur will produce 646.97 grams of SO2?

Question

The numbers in the equation are subscripts

*in front of compound are coefficients to balance the equation 

please show your work, so i can see how you did it(:

Answer 1

The question should be asking "what mass of O2 is needed to produce 646.97 g SO3 (not SO2)?

2S + 3O2 ===> 2SO3

moles of SO3 represented by 646.97 g = 646.97 g x 1 mole/80.066 g = 8.0805 moles SO3

moles of O2 needed to form 8.0805 moles SO3 = 8.0805 moles SO3 x 3 moles O2/2 moles SO3 = 12.121 moles O2

The above calculation is based on the mole ratio of 3 moles O2 : 2 moles SO3 in the balanced equation.

 

MASS O2 required = 12.121 moles O2 x 32 g/mole = 387.86 grams O2 needed.