How do you do redox titration problems?

1 Answer
anor277
Jul 11, 2017

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.

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