[buda]

This is a standard experiment, of course I know which halogens are most and least reactive, but I have to prove it experimentally.

I was thinking of taking a halogen compound, let's say KI [pottasium iodide], and then adding Chlorine, and naturally there should be a displacement reaction, but seeing whether one took place or not may not be easy, so I guess I should add some silver nitrate (or something similar) to get a precipitate to check the color of the precipitate, but then I get a bit stuck because comparing colors (with perticipates of controled trials where I know exactly what compound I'm dealing with) may be a bane because of the colour change due to UV light.

any suggestions?

[Mitch]

Could you check melting points of the products?

[buda]

but the products would still be a solution of the compound of the metal and more reactive halogen plus seperatly floating in the solution would be ions of the less reactive halogen.

I would have to seperate them some how to check their melting points. What do you think could work?

[Mitch]

Can't you let the solution evaporate? Then the salt formed will salt out while the non-reacted halogen will evaporate away.

[AWK]

I was thinking of taking a halogen compound, let's say KI [pottasium iodide], and then adding Chlorine, and naturally there should be a displacement reaction, but seeing whether one took place or not may not be easy, so I guess I should add some silver nitrate (or something similar) to get a precipitate to check the color of the precipitate, but then I get a bit stuck because comparing colors (with perticipates of controled trials where I know exactly what compound I'm dealing with) may be a bane because of the colour change due to UV light.

Taking into account Cl2. Br2 and I2 it it quite easy.
1.To a solution of potassium iodide add a fee drops of CHCL3 or CCL4, then a fwe drops of chlorine or bromine water. and shake the mixture, The organic layer will become violet.
2. The same with KBr - organic layer will become red-brown

Such a reaction is impossible with F2 - it reacts with water.

[buda]

I'm sorry for not replying earlier.
I'm afraid I don't quite understand how your proposition works.
I would like to ask another thing, what is it really that makes the elements lower down in the groups, more reactive than those higher up, as in Na less reactive than K, and I less reactive than Cl?