# Question #82a89

Jun 20, 2016

I think you need to research the contact process.

#### Explanation:

AFAIK, elemental sulfur is oxidized stepwise to give $S {O}_{3}$:

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

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

The sulfur trioxide could be directly treated with water to give ${H}_{2} S {O}_{4}$. I have seen a couple of plants, and it is an incredibly dirty and smelly process. Of course, both oxidations are catalyzed; I think supported ${V}_{2} {O}_{5}$ is the catalyst of choice.

One thing the reaction has got going for it, is that both oxidations are exothermic. Sulfur trioxide may be directly converted to sulfuric acid:

$S {O}_{3} \left(g\right) + {H}_{2} O \left(g\right) \rightarrow {H}_{2} S {O}_{4} \left(a q\right)$

But this opens another can of worms. Usually sulfuric acid is reacted directly with sulfur trioxide to give oleum, ${H}_{2} {S}_{2} {O}_{7}$, which is the feedstock for ${H}_{2} S {O}_{4}$.