[hoshi4ever]

when conducting the experiment  1cm³ of chlorine water is added to 1cm³ of potassium iodide and 1cm³ of hexane is add then. suppose the displacement occurs and give a upper purple layer and lower orange layer. but what during the experiment get is 2 layer of colourless solution. why? and what is the main purpose of hexane?

[Arkcon]

OK, lets work together to begin to help you figure this out for yourself.  (That is how we help on this forum, you can read that in the Forum Rules, in red, at the top of each forum page.)  Start by writing the chemical equation.  What is chlorine water?  What chemical did you mix it with -- the formula, not the name in words?  Then we can determine what was supposed to happen, what did happen, and we'll mention what the hexane is for, because that's a little tough to figure out, based only on observations.

[hoshi4ever]

chlorine water Cl2 is mixed with potassium iodide KI. theoretically the reaction will be Cl2 + 2KI --> 2KCl + I2. and the I2 will show is colour properties in hexane is purple and in water is yellow. Result I get during the experiment is both layer colourless. 

[Borek]

You are right about what should happen. If it didn't happen - there was something wrong with the reagents used.