Chemistry Forums for Students > High School Chemistry Forum

half reaction of Potassium permanganate

(1/1)

tigernk:
Potassium permanganate reacts with sulfuric acid and potassium bromide to form potassium sulfate, manganese(II) sulfate, bromine, and water. Balance this equation using the half-reaction method. The reaction takes place in an acidic solution.

Donaldson Tan:
first, check your data booklet for the relevant half-equations

(1) MnO4- (aq) + 8H+ (aq)  +5e -> 4H2O (l)  + Mn2+ (aq)

(2) 2Br- (aq) -> Br2 (aq)  + 2e

Equation (1) uses up 5e while Equation (2) uses up 2e. Since the lowest common multiple between 5 and 2 is ten, we ought to apply the mole-multiplier of 2 and 5 respectively on each equation, such that they involve 10e each.

The modfied half equations would be:

2MnO4- (aq) + 16H+ (aq)  +10e -> 8H2O (l)  + 2Mn2+ (aq)

10Br- (aq) -> 5Br2 (aq)  + 10e

Next, combine both modified half-equations to obtain the final chemical equation, ie:

2MnO4- (aq) + 16H+ (aq)  + 10Br- (aq) -> 8H2O (l)  + 2Mn2+ (aq) + 5Br2 (aq)

Navigation

[0] Message Index