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Half-reactions

Posted: Tue Feb 14, 2017 9:06 pm
by Xin Huang 3E
For half-reactions, when do we leave out the water or other substances, and when do we incorporate them?
E.g. For Q7 in Winter 2013 Midterm, I notice the answer indicates:
2Mn2+(aq)+8H2O(l) --> 2MnO4-(aq)+16H++ 10e- for the anode;
Why don't we write instead: 2Mn2+(aq) --> 2Mn7+(aq)+10e- ?

Re: Half-reactions

Posted: Tue Feb 14, 2017 9:08 pm
by Ara Yazaryan 1E
For this case water is not being included in the reaction, rather the half reaction is occurring in an acidic solution. These means we use water and H+ to balance our oxygen atoms.