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Redox half equations?

Hi does anyone have any tips for working out half equations and then using 2 half equations to form the full equation?

Eg
What would the half equations be for:

MnO4- + 8H+ + 5Fe2+ ——> Mn3+ +5Fe3+ + 4H2O


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Original post by ImAz
Hi does anyone have any tips for working out half equations and then using 2 half equations to form the full equation?

Eg
What would the half equations be for:

MnO4- + 8H+ + 5Fe2+ ——> Mn3+ +5Fe3+ + 4H2O


Posted from TSR Mobile


You have to select first the species that is oxidised (or reduced) and it's product.

In your example there is one species with iron in on the LHS and one on the RHS.

Start there.

Balance the half equation by addition of hydrogen ions, water or just electrons. In this case you only need electrons.

Fe2+ --> Fe3+ + 1e

Then deal with the manganese species:

MnO4- --> Mn2+

You need to remove four oxygen atoms from the LHS. You do this by adding eight hydrogen ions. This makes four water molecules on the RHS.

The manganese atom changes from +7 to +2 so it must absorb 5 electrons on the LHS

MnO4- + 8H+ + 5e --> Mn2+ + 4H2O

and hey presto!
Reply 2
Avatar for Borek
Borek
4
Mn3+ or Mn2+?
Reply 3
Avatar for ImAz
ImAz
OP
6
Original post by charco
You have to select first the species that is oxidised (or reduced) and it's product.

In your example there is one species with iron in on the LHS and one on the RHS.

Start there.

Balance the half equation by addition of hydrogen ions, water or just electrons. In this case you only need electrons.

Fe2+ --> Fe3+ + 1e

Then deal with the manganese species:

MnO4- --> Mn2+

You need to remove four oxygen atoms from the LHS. You do this by adding eight hydrogen ions. This makes four water molecules on the RHS.

The manganese atom changes from +7 to +2 so it must absorb 5 electrons on the LHS

MnO4- + 8H+ + 5e --> Mn2+ + 4H2O

and hey presto!


This is AMAZING!
You've literally made it so easy for me to understand haha
Thanks!


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