What is the reaction between sulfur dioxide, $"SO"_2$ , and potassium dichromate, $"K"_2 "Cr"_2"O"_7$ ?

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Answer 1 · 2017-04-01T15:07:46

In presence of $"H"_2"SO"_4$ ,potassium dicromate reacts with $"SO"_2$ as following.

$3"SO"_2$ + $"K"_2"Cr"_2"O"_7$ + $"H"_2"SO"_4$ $->$ $"K"_2"SO"_4$ + $"Cr"_2("SO"_4)_3$ + $"H"_2"O"$

Answer 2 · 2017-04-01T15:13:34

Well, we would assume that $"sulfur dioxide"$ is oxidized to $"sulfur trioxide"$ .

I think this is done industrially by $V_2O_5$ .

But sulfur is oxidized to from $S(+IV)$ to $S(+VI):$

$SO_2(g) +H_2O(l) rarr SO_3(g) +2H^(+) + 2e^(-)$ $(i)$

And dichromate is reduced from $Cr(+VI)$ to $Cr(+III):$

$Cr_2O_7^(2-) +14H^(+) +6e^(-)rarr 2Cr^(3+) +7H_2O(l)$ $(ii)$

We add $3xx(i) + (ii)$ to eliminate the electrons:

$Cr_2O_7^(2-) +8H^(+) +3SO_2(g) rarr 2Cr^(3+) +4H_2O(l)+3SO_3(g)$

Are mass and charge balanced? This is your problem not mine.

What is the reaction between sulfur dioxide, "SO"_2"SO"_2, and potassium dichromate, "K"_2 "Cr"_2"O"_7"K"_2 "Cr"_2"O"_7 ?