What would occur in the reaction between $potassium permanganate$ $"potassium permanganate"$ , $K M n O_{4}$ $KMnO_4$ and $sodium sulfite$ $"sodium sulfite"$ , $N a_{2} S O_{3}$ $Na_2SO_3$ ?

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What would occur in the reaction between $potassium permanganate$ $"potassium permanganate"$ , $K M n O_{4}$ $KMnO_4$ and $sodium sulfite$ $"sodium sulfite"$ , $N a_{2} S O_{3}$ $Na_2SO_3$ ?

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Answer 1 · 2016-10-06T09:28:46

A redox reaction occurs. Sulfite should be oxidized to sulfate. Permanganate ion should be reduced to $M n^{2 +}$ $Mn^(2+)$ .

Explanation:

$Reduction half equation: M n (V I I +) \to M n (I I +)$ $"Reduction half equation: "Mn(VII+) rarr Mn(II+)$

$M n O_{4}^{-} + 8 H^{+} + 5 e^{-} \to M n^{2 +} + 4 H_{2} O$ $MnO_4^(-) +8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_2O$ $(i)$ $(i)$

$Oxidation half equation: S (I V +) \to S (V I +)$ $"Oxidation half equation: "S(IV+) rarr S(VI+)$

$S O_{3}^{2 -} + H_{2} O \to S O_{4}^{2 -} + 2 H^{+} + 2 e^{-}$ $SO_3^(2-) +H_2O rarr SO_4^(2-) + 2H^(+) + 2e^(-)$ $(i i)$ $(ii)$

Both equations are (I think) balanced with respect to mass and charge, as they must be if they reflect reality. The overall redox reaction excludes the electrons; so we take $2 \times (i) + 5 \times (i i)$ $2xx(i)+5xx(ii)$ :

$2 M n O_{4}^{-} + 5 S O_{3}^{2 -} + 6 H^{+} \to 2 M n^{2 +} + 5 S O_{4}^{2 -} + 3 H_{2} O$ $2MnO_4^(-) +5SO_3^(2-)+6H^(+)rarr 2Mn^(2+) + 5SO_4^(2-)+3H_2O$

Which is (I think) balanced with respect to mass and charge.

So what would you observe in this reaction? $M n O_{4}^{-}$ $MnO_4^-$ is strongly coloured, and gives a beautiful deep purple solution. On the other hand, $M n^{2 +}$ $Mn^(2+)$ is almost colourless (very concentrated solutions are a pale rose). And thus this redox reaction is self-indicating, and proposes that $2$ $2$ $equiv$ $"equiv"$ permanganate reacts with $5$ $5$ $equiv$ $"equiv"$ of sulfite.

How did I know the oxidation/reduction products? Experience and practice, and actually doing the titrations and observing and explaining the colour change.

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What would occur in the reaction between $potassium permanganate$ $"potassium permanganate"$ , $K M n O_{4}$ $KMnO_4$ and $sodium sulfite$ $"sodium sulfite"$ , $N a_{2} S O_{3}$ $Na_2SO_3$ ?

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What would occur in the reaction between potassium permanganate"potassium permanganate", KMnO4KMnO_4 and sodium sulfite"sodium sulfite", Na2SO3Na_2SO_3?

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What would occur in the reaction between $potassium permanganate$ $"potassium permanganate"$ , $K M n O_{4}$ $KMnO_4$ and $sodium sulfite$ $"sodium sulfite"$ , $N a_{2} S O_{3}$ $Na_2SO_3$ ?