Question

How do you do redox titration problems?

Answer 1

Well you require a stoichiometrically balanced equation, which represents the redox transfer....... determination of oxalic acid by potassium permanganate is a good example.

Explanation:

`"Permanganate ion,"` `MnO_4^(-)` is a commonly used reagent for redox titrations........Why? Well because as `Mn(VII+)` it is strongly coloured RED; and `Mn(II+)`, its reduction product is almost colourless.....and we must supply the reduction half equation....

Deep purple permanganate ion, `Mn(VII+)`, is reduced to colourless `Mn^(2+)`:

`MnO_4^(-)+8H^+ + 5e^(-) rarr Mn^(2+) + 4H_2O` `(i)`

Charge and mass are balanced as required......

Meanwhile oxalic acid is oxidized to carbon dioxide.......`C(+III)rarrC(+IV)`.........

`C_2O_4^(2-) rarr 2CO_2(g)uarr+2e^-` `(ii)`

We takes `2xx(i)+5xx(ii)` to eliminate the electrons.......

`2MnO_4^(-)+6H^++5HO(O=)C-C(=O)OH(aq)rarr 2Mn^(2+) + 10CO_2(g)uarr+ 8H_2O(l)`

Vizualization of the endpoint is made easy by the disappearance of the colour of permanganate.... The stoichiometry follows the given equation.