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Displacement reactions

Hello everyone.

I'm slightly confused with reactivity series and displacement reactions.

I know the reactivity series for metals and anions, so for example Potassium is higher in the reactivity series than Iron. Same goes for zinc being above copper.

In a salt, displacement occurs only if the element in the salt is lower down in the reactivity series than the element it is reacted with, right? So for example,
copper sulfate and zinc would form copper and zinc sulfate?

Why doesn't this work for halogens though? In this example below, why wouldn't there be a displacement? Or is the displacement only with metals here...?

For electrolysis, it is the elements lower down in reactivity table which are produced on the cathode and anode. I feel like I'm mixing that up with the question here.. ;/

Screen Shot 2017-11-01 at 14.50.32.png130.4KB

Reply 1

Pigster

KCl(aq) exists as K+(aq) and Cl-(aq). They aren't attached to each other, they are floating free of each other.

If you add in some F-(aq) they will be floating free of the K+(aq) also.

You mixture will just contain K+, Cl- and F- all (aq).

Now, if you were to add F2, rather than F-, then there would be redox (I don't know which exam board you're taking, but it might be best to avoid the word displacement).