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Which process is an oxidation?


A] 2 H+(aq) + CO32-(aq) H2O(l) + CO2(g)

B] Fe3+(aq) Fe2+(aq)

C] 2 CrO42-(aq) + 2 H+(aq) Cr2O72-(aq) + H2O(l)

D] Ba2+(aq) + CrO42-(aq) BaCrO4(s)

E] MnO2(s) MnO4-(aq

Verified Answer :

syed514

The problem has to do with oxidation states of the matter. The oxidation state of oxygen will always be -2 with the exception of peroxides which will have a state of -1. The overall balanced state of chemical compounds will be 0, so the oxidation state of Mn in MnO2 will be +4. The oxidation state of MnO4- will then be +7 to balance out to the negative one charge. The state change from +4 to +7 is 3, thus three electrons have to be lost in order for this to happen; a loss of a charge of -3 results in an increase of charge of 3. Oxidation is always the process of 'losing' electrons.

E] MnO2(s) MnO4-(aq

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