Does HCL react with iodine?If not, why did I find my iodine solution turn yellow after I added HCL?

Question

the Iodine solution :iodine dissolved in water solution

I'm pretty sure I did not mix the wrong reagents.I did it three times, all of them have the same result.

Answer 1

HCl should have no reaction with iodine because iodine is less reactive than chlorine, displacement reaction of halogen should not occur.

I think it is because iodine solution contains I3(-) ion that can be detected with starch but ALSO in acidic environments. Therefore, it turns yellow because you added it to HCl which is an acid in aqueous state.

ps. I don't know if you were saying iodine dissolves in water to form a solution OR you were talking about the Tincture of iodine, but my answer is for the latter one.

Answer 2

Dear Nikki,

There is an unstable compound:
RbICl2
Look up to see if there is an analogous:
HICl2 or maybe you have KICl2
and find out what color it is in solution!

The reaction between HCl and I2 will be very different when a polarising solvent like water; liquid ammonia; HCN are used as solvents to facilitate a reaction. You would need to consider all possible combinations of available elements!

Look up: POLYHALIDES and GILLESPIE-NYHOLM Rules
Polyhalides form irregular long chains and may well absorb in the visible.

This all may be or may not be relevent to what you have observed but see if any school or college magazine would be interested in your observations and subsequent Library Research.

CopyLeft:RCat

Answer 3

I2 cannot displace Cl from HCl since Cl is more electronegative (iodine cannot "steal" away electrons from Cl-) If you had a reaction then I2 would become I- which is colourless, thus your solution would have lost its colour.

The change in colour is due to the change in the pH, but I am not sure exactly why.

Maybe you can have a complex formation with Cl- , that is
I2Cl(-). I2 reacts with I- forming the coloured and highly soluble I3(-), so it is possible that it can react with Cl- forming a (differently) coloured complex.
{edit} Well this, although promising, is probably not the case, since Cl- from salts is not enough to change the colour to yellow according to http://jchemed.chem.wisc.edu/jcesoft/CCA/CCA3/MAIN/HALOGEN/PAGE1.HTM

so either it is a matter of pH or you mixed the wrong solutions.