# How could sulfur be oxidized to SO_3 by the action of NO_3^(-)?

##### 1 Answer
Jan 30, 2016

Sulfur is oxidized to sulfur trioxide. Nitric acid is reduced to nitric oxide, $N {O}_{2}$. Here, we do NOT use oxygen gas as a reactant, and use standard redox processes.

#### Explanation:

Oxidation:

$S + 3 {H}_{2} O \rightarrow S {O}_{3} + 6 {H}^{+} + 6 {e}^{-}$ $\left(i\right)$

Zerovalent sulfur is oxidized to $S \left(V {I}^{+}\right)$.

Reduction:

$N {O}_{3}^{-} + 2 {H}^{+} + {e}^{-} \rightarrow N {O}_{2} + {H}_{2} O$ $\left(i i\right)$

So, $6 \times \left(i i\right) + \left(i\right) =$

$S + 6 N {O}_{3}^{-} + 6 {H}^{+} \rightarrow S {O}_{3} + 6 N {O}_{2} + 3 {H}_{2} O$; alternatively:

$S + 6 H N {O}_{3} \rightarrow S {O}_{3} + 6 N {O}_{2} + 3 {H}_{2} O$

This is balanced with respect to mass and charge. It would not be a feasible reaction in practical terms. Industrially, sulfur trioxide is produced from sulfur dioxide and oxygen directly with some form of supported catalysis. It must be an incredible dirty and smelly process.