6th edition, 14.17

[Hai-Lin Yeh 1J]

(a) Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride.

How would we start off this question? I'm not sure where they got Fe2+ -> Fe3+ from and MnO4- -> Mn2+

[Chem_Mod]

The best way to tackle these kinds of problems is to practice. When a half reaction contains permanganate, it's always going to have a redox pair between MnO₄^- and Mn²⁺. Same thing with iron, as the redox pair is usually between an Fe²⁺ and an Fe³⁺. Whenever you want to balance oxygens, we usually add H₂O, and then add H+ to balance the hydrogens from that added H₂O, after which we balance charge with addition of electrons.

[annabel 2A]

Why is it Fe2+ --> Fe3+ and not Fe2+ --> Fe or any of the other ones? Should we just assume that it will be Fe2+ --> Fe3+?