7.0 moles of sulfur atoms and 10 moles of oxygen molecules are combined to form the maximum amount of sulfur trioxide, how many moles of which reactant remain unused at the end of the reaction?

1 Answer
Sep 16, 2016

S(s) +3/2O_2(g) rarr SO_3(g)

Clearly sulfur is in excess.......

Explanation:

.........And oxygen is in deficiency.

Given 10 mol of dioxygen gas, at most, 6.67 mol of sulfur trioxide can be generated. This is clearly indicated by the stoichometric equation. Should the reaction proceed to completion (which is unlikely) there will be approx. 0.33 mol sulfur unreacted.

Industrial production of sulfur trioxide (the precursor to sulfuric acid) relies on the Contact Process: oxidation to SO_2, and then catalyzed oxidation of SO_2 to SO_3. It must be an incredibly dirty and smelly process, yet it is undoubtedly vital to our industrial society.