Question

What is the redox equation for the oxidation of potassium chloride to chlorine gas by potassium permanganate in the presence of sulfuric acid?

Answer 1

`KMnO_4 + 4H_2SO_4 + 5KCl rarr MnSO_4 + 5/2Cl_2 +3K_2SO_4 +4H_2O`

Explanation:

This is a redox reaction. Permanganate ion is reduced to `Mn^(2+)`, and chloride ion is oxidized to chlorine gas:

`"Oxidation reaction:"`

`Cl^(-) rarr 1/2Cl_2 + e^-` `(i)`

`"Reduction reaction:"`

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

In each reaction, both charge and mass are balanced (are they?). And the equations must be balanced if they reflect chemical, i.e. physical reality. The overall reaction eliminates the electrons, and thus I take `5xx(i) + (ii)`.

`MnO_4^(-) + 8H^(+) + 5Cl^(-) rarr Mn^(2+) + 5/2Cl_2 +4H_2O`

This is the same reaction as given above, however, there, we used neutral entities not ions.

What we would observe in this reaction? The intense purple/red colour of permanganate ion would dissipate to give almost colourless `Mn^(2+)` ion.