1.

Addition of CI_(2) to KI solution gives it a brown colour but excess of CI_(2)turns it colourless. Explain.

Answer»

Solution :`Cl_(2)` being a stronger oxidising agent than `I_(2)`, FIRST oxidises KI to give `I_(2)` which imparts brown COLOUR to the solution.
`2 KI (aq) + Cl_(2)(g) rarr 2 KCI(ag) + underset(("Browin"))(I_(2)(s))`
If, however, `Cl_(2)` is passed in excess, the `I_(2)` THUS formed gets further oxidised to iodic acid `(HIO_(3))` which is colourless.
`5 Cl_(2) + I_(2) + 6 H_(2)O rarr 10 HCI + underset(("Colourless"))(2HIO_(3))`


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