Oxidation Numbers

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Oxidation Numbers

Postby 605168557 » Sat Mar 16, 2019 10:47 pm

How do you know the oxidation number for a species? For example in the reaction MnO4- (aq) + H2C2O4 (aq) --> Mn2+ (aq)+ CO2 (g) the oxidation number for Mn decreases from +7 to +2 and the oxidation number for C increases from +3 to +4 but how do you get these values other than the +2 that is shown on the product side for Mn2+ ? because that is the first step before balancing anything and I'm confused as to how that is already known.

MariahClark 2F
Posts: 60
Joined: Wed Nov 15, 2017 3:04 am

Re: Oxidation Numbers

Postby MariahClark 2F » Sat Mar 16, 2019 10:53 pm

It is helpful to memorize the oxidation numbers for common elements like for oxygen and hydrogen. So for example, in MnO4 minus; oxygen's oxidation number is -2. There are 4 oxygens which totals up to a -8. A +8 would be needed to balance out the compound but since the compound is -1, Mn's oxidation number should be +7. I hope this makes sense to you because it can be sort of confusing.

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