KI solution color change in tap water.

[amorale]

Hello,

My question is regarding a reaction with KI with some chemical in tap water.
Today I was working on a lab at school and had a beaker with about 10ml of 100mM KI in it, when I went to clean it and put tap water in the solution it automatically turned clear yellow.

So I was wondering what may have been in the tap water that made it react that way and also what exactly was being produce in the reaction that made the color yellow.

I know from previews experiments that if you increase I3- concentration in a solution it will turn yellow after a couple of minutes, so was I3- being form in this reaction or was it another Iodine ion?

Thank You, if you need me to clarify something please just ask.

 

[Simon Bridge]

There seems to be a lot of things that will turn yellow when KI is added to it.
It could be just that the KI was old and it had some elemental iodine in it.