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    When iodine and chlorine are mixed with cyclo-hexane, why does Iodine form a purple layer on top of chlorine, why this colour and why does this happen rather than the other way round?

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    Cyclo-hexane does not mix with water, which the chlorine/iodine are in solution too. So they form two layers, with cyclo-hexane forming on top of the lower layer as it's added on top of that solution. Now I'm guessing this is a displacement (as you mentioned coursework in your pm), so chlorine displaces iodines position in whatever molecules, so pure iodine is produced. And now iodine is a dark brown sort of colour, and so the lower layer will turn this colour. However iodine does also dissolve in cylcohexane, and it is more soluble in cyclohexane than it is in water, and so a purple colour is formed on the top layer (which is the cylohexane). This colour is simply the colour of iodine being shown more clearly as it dissolves better in cyclohexane.

    Just a note to your question, you mention why does it not happen the other way around, I assume you mean why not purple at the bottom. Firstly the colour of chlorine should be less visible as it becomes used in the displacement and forms whatever, say for example potassium chloride. So the colours of both layers should be due to the iodine being displaced. And now I'm guessing the purple is on top as the solution containing iodine was the first in the beaker, and so when cyclohexane is added in simply forms on top as it does not mix. If cyclohexane was added first and then the solution it may be the other way around, though if there's any principle that governs this I'm not so sure so I think its simply to do with the order they are added into the beaker.
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    (Original post by AndroidLight)
    Cyclo-hexane does not mix with water, which the chlorine/iodine are in solution too. So they form two layers, with cyclo-hexane forming on top of the lower layer as it's added on top of that solution. Now I'm guessing this is a displacement (as you mentioned coursework in your pm), so chlorine displaces iodines position in whatever molecules, so pure iodine is produced. And now iodine is a dark brown sort of colour, and so the lower layer will turn this colour. However iodine does also dissolve in cylcohexane, and it is more soluble in cyclohexane than it is in water, and so a purple colour is formed on the top layer (which is the cylohexane). This colour is simply the colour of iodine being shown more clearly as it dissolves better in cyclohexane.

    Just a note to your question, you mention why does it not happen the other way around, I assume you mean why not purple at the bottom. Firstly the colour of chlorine should be less visible as it becomes used in the displacement and forms whatever, say for example potassium chloride. So the colours of both layers should be due to the iodine being displaced. And now I'm guessing the purple is on top as the solution containing iodine was the first in the beaker, and so when cyclohexane is added in simply forms on top as it does not mix. If cyclohexane was added first and then the solution it may be the other way around, though if there's any principle that governs this I'm not so sure so I think its simply to do with the order they are added into the beaker.

    ah, thank you again! =D
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    In cyclohexane, iodine is purple/pink, bromine is a strong brown-orange and chlorine is pale green.
    The colours show up more vivid in Cyclohexane than water.
    Remember that there is no reaction going on, just solutions getting mixed.

    Halogen: Cl2
    Colour in water: Pale-green
    Colour in cyclohexane: Pale-green

    Halogen: Br2
    Colour in water: Orange
    Colour in cyclohexane: Orange

    Halogen: I2
    Colour in water: Brown
    Colour in cyclohexane: Violet

    Cyclohexane is non-polar wereas water is polar.
 
 
 
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