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Solution: Which element is oxidized and which is reduced in the follow...


Which element is oxidized and which is reduced in the following reactions?

(b) 3 Fe(NO3)2 (aq) + 2 Al (s) → 3 Fe (s) + 2 Al(NO 3)3 (aq)

Video Transcript

Hey guys, so here we have a balanced chemical equation and from this balanced chemical equation we're going to have to figure out what elements have been oxidised and what elements have been reduced. To help us with this remember our chart, Leo the lion goes GER, to guide us. So the reaction that we're looking at here is we have 3 moles of iron 2 nitrate reacts with 2 moles of aluminium solid to produce 3 moles of iron solid plus 2 moles of aluminium nitrate.

Now here's a thing, first of all our polyatomic ion of nitrate does not change. It's NO3 on both sides and if the composition or the way the polyatomic looks doesn't change then the oxidation numbers in it don't change. So it's NO3 on both sides so just ignore it. Here we're looking at iron, here this 2 came from the iron meaning this is the iron 2 ion so its oxidation over here is +2 and then we're going to say aluminium here is by itself in its natural or standard state so it's zero, same thing here with this iron, by itself in its standard natural state so it's zero. 3 here came from aluminium so here its oxidation number is +3.

Now, we're going to say that this is FE2+ on the reactant side, it goes from being +2 to being in this form where it's zero. So it's oxidation number decreased so FE2+ has been reduced. Now we're looking at aluminium solid here, aluminium solid goes from being zero to being in its +3 form here so it's oxidation number increased therefore aluminium solid was oxidised. So that's what we would say in terms of what's been oxidised and what's been reduced.