How to formulate and balance a redox equation under acidic conditions

In a reaction between  MnO4- and Fe2+ we are told MnO4- goes to Mn2+ and Fe2+ goes to Fe3+. We then need to derive the redox equation for the reaction occuring. First we need to idenfity which species are being reduced and which are oxidised. We can use ' OIL RIG' when referring to electrons to help us.OxidationIsLoss of electronsReduction Is Gain of electronsMnO4- (where Mn has a +7 oxidation state) gains electrons, hence is reduced, to Mn2+ and Fe2+ loses electrons, hence oxidised, to Fe3+. Starting with the reduction half equation,    1. Write out the reactant and product                   MnO4-        ------>   Mn2+2. Use H2O to balance the oxygen                    MnO4-        ------>   Mn2+ + 4H2O3. Use H+ (as under acidic conditions) to thenbalance the other side of the equation                  MnO4- + 8H+        ------>   Mn2+ + 4H2​O4. Add electrons to balance the charges                MnO4- + 8H+ + 5e-    ------>   Mn2+ + 4H2​OFor the oxidation half equation,1. Write out the reactant and product                  Fe2+   ------->   Fe3+2. Balance the equation using electrons                Fe2+ ------->   Fe3+ + e-To combine the reduction and oxidation half equations we need to have the same number of electrons. Multiply the oxidation half equation by 5 to give us 5Fe2+  ------->   5Fe3+ + 5e-Then add the two half equations together, canceling any like terms (the electrons) from both sides. The overall redox equation is therefore 5Fe2+ + MnO4- + 8H+   ------>  5Fe3+ + Mn2+ + 4H2​O 

KD
Answered by Kiera D. Chemistry tutor

3241 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

a) How can an element be classified as a transition metal, considering only electronic arrangement? (1 mark) b) In terms of electrons, why is aqueous copper(II) sulphate solution red? (3 marks) c) EDTA is a bidentate ligand. What is a bidentate ligand?(2)


What are optical isomers?


What is a disproportionation reaction?


Calculate the mass of sodium amide needed to obtain 550 g of sodium azide, assuming there is a 95.0% yield of sodium azide. Give your answer to 3 significant figures.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning