Determining Oxidation State

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Layal Suboh 1I
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

Determining Oxidation State

Postby Layal Suboh 1I » Wed Feb 20, 2019 4:38 pm

Hello,

Today in lecture Dr. Lavelle discussed the chem reaction 8H+ + MnO4- + 5Fe2+ --> Mn2+ +5Fe3+ + 4H2O

How did we determine that iron was oxidized and lost 5 electrons? I know that manganese was reduced because its oxidation number went from +7 to +2, and iron was oxidized because it went from 2+ to 3+, but how do you know that iron lost 5 electrons?


Thanks

hazelyang2E
Posts: 57
Joined: Fri Sep 28, 2018 12:23 am

Re: Determining Oxidation State

Postby hazelyang2E » Wed Feb 20, 2019 4:43 pm

The reason why iron lost 5 electrons is because the entire oxidation reaction of Fe2+ --> Fe3+ + 1e- was multiplied by 5 so that the 5e- in the reduction reaction (8H+ + MnO4- + 5e- --> Mn2+ + 4H2O) would cancel out in the overall oxidation reduction reaction.

Emma Scholes 1L
Posts: 62
Joined: Fri Sep 28, 2018 12:18 am

Re: Determining Oxidation State

Postby Emma Scholes 1L » Wed Feb 20, 2019 4:44 pm

You know Fe lost 5 electrons because originally there are 5 Fe 2+ which has a total charge of 10+. After the reaction there is 5 Fe 3+ which has a total charge of 15+. In order to go from 10+ to 15+, 5 electrons must be lost.


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