# How do we represent the oxidation of oxalate ion by permanganate ion?

## How do we represent the oxidation of oxalate ion by permanganate ion by the half-equation method? What colour change would we observe in the titration?

Sep 11, 2017

$\text{Permanganate ion}$ is coloured a bright purple....

#### Explanation:

And conveniently, it is reduced to $M {n}^{2 +}$, which is almost colourless. This change is very recognizable, and the stoichiometric endpoint is very accessible.

$\text{Reduction half equation:}$

${\underbrace{M n {O}_{4}^{-}}}_{\text{bright purple}} + 8 {H}^{+} + 5 {e}^{-} \rightarrow M {n}^{2 +} + 4 {H}_{2} O \left(l\right)$ $\left(i\right)$

$\text{Oxidation half equation:}$

${C}_{2} {O}_{4}^{2 -} \rightarrow 2 C {O}_{2} \left(g\right) + 2 {e}^{-}$ $\left(i i\right)$

And so we take $2 \times \left(i\right) + 5 \times \left(i i\right)$ to give.....

$2 M n {O}_{4}^{-} + 5 {C}_{2} {O}_{4}^{2 -} + 16 {H}^{+} \rightarrow 2 M {n}^{2 +} + 10 C {O}_{2} \left(g\right) + 8 {H}_{2} O \left(l\right)$