# How would we represent the reaction of SO_2 with K_2Cr_2O_7 to give SO_3?

May 6, 2017

We would assume that the sulfur dioxide is oxidized to sulfur trioxide.

#### Explanation:

${\stackrel{I V +}{\text{SO"_2 +H_2O rarr stackrel(VI+)"SO}}}_{3} + 2 {H}^{+} + 2 {e}^{-}$ $\left(1\right)$

And dichromate is reduced to chromic ion......:

$C {r}_{2} {O}_{7}^{2 -} + 14 {H}^{+} + 6 {e}^{-} \rightarrow 2 C {r}^{3 +} + 7 {H}_{2} O$ $\left(2\right)$

And we take $3 \times \left(1\right) + \left(2\right)$ to eliminate the electrons:

$C {r}_{2} {O}_{7}^{2 -} + 8 {H}^{+} + 3 S {O}_{2} \rightarrow 2 C {r}^{3 +} + 3 S {O}_{3} + 4 {H}_{2} O$

Are charge and mass balanced? If the answer is no then we cannot accept the reaction. Industrially, the oxidant is oxygen gas. I do not know if the reaction would proceed as written.