oxidation-reduction

Your equations looks okay to me. Only one molecules of chlorine is reduced to ions. The other two Cl- ions in FeCl2 are unchanged.

Found this question in my NAS book and I just dont get something.

Q is

Separate oxidation-reduction reactions in half equations.

2FeCl2 + Cl2 --> 2FeCl3

I can see it must be something on the lines of

Fe2+ ---> Fe3+ + e-
Cl2 + 2e- --> 2Cl-

But that combines to give

2Fe2+ + Cl2 ----> 2Fe3+ 2Cl-
(I can perhaps see how 2Fe3+ 2Cl- will give FeCl3
But what about the FeCl2?? What am I missing?)


Thanks.

Are we talking about spectator ions of something?

What bothers me is when I work the other way round ,use my 2 half equations and then combine - I dont get back to their original. Can I just shove in some Cl- and call them spectator ions or something?

That combines to 2Fe2+ + Cl2 ==> 2Fe3+ + 2Cl-
Then add in 4 spectator Cl- ions to each side to give:

2Fe2+ + Cl2 + 4Cl- ==> 2Fe3+ + 6Cl-
Which gives:
2FeCl2 + Cl2 --> 2FeCl3

therefore you were correct. :P

Wonderful stuff black dog - cheeers.