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14.17 textbook problem

Posted: Wed Feb 03, 2016 3:59 pm
by Elizabeth Hoang 2C
For 14.17, we are asked to write the balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride. How do we know which half reaction to use since we are given 4 different types (i.e. K+, MnO4-, Fe2+, Cl-)?

Re: 14.17 textbook problem

Posted: Wed Feb 03, 2016 7:22 pm
by Kim Vu 2G
I have a follow up question to this problem. So I noticed that in the solution's manual, there is no presence of Cl anywhere in the reaction. Is this because the Cl has completely dissociated due to the acidity of the reaction?

Re: 14.17 textbook problem

Posted: Thu Feb 04, 2016 2:50 pm
by Kayla Tran 1E
We ignore both the K+ and Cl- ions because they dissociate in solution and don't undergo any change. Therefore they are spectator ions and if you included them in a chemical equation for the overall reaction they would cancel out anyways. Then you are only left with Fe2+ and MnO4- to determine which is the reduction and which is the oxidation reaction.

I was wondering after you narrow it down, how do you know what the equations should be since you aren't given any products they should form?
For example how do you know MnO4- goes to Mn2+ or that Fe2+ goes to Fe3+?