# 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?

Sep 16, 2016

$S \left(s\right) + \frac{3}{2} {O}_{2} \left(g\right) \rightarrow S {O}_{3} \left(g\right)$

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

#### Explanation:

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

Given $10$ $m o l$ of dioxygen gas, at most, $6.67$ $m o l$ 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. $0.33$ $m o l$ sulfur unreacted.

Industrial production of sulfur trioxide (the precursor to sulfuric acid) relies on the Contact Process: oxidation to $S {O}_{2}$, and then catalyzed oxidation of $S {O}_{2}$ to $S {O}_{3}$. It must be an incredibly dirty and smelly process, yet it is undoubtedly vital to our industrial society.