lodine is liberated in the reactions between `KI and Cu^(2+)`, but chlorine is not liberated when KCI is added to `Cu^(2+)`, why? 

Explanation

Iodide is a strong reducing agent. Though `Cu^(2+)` is a mild oxidising agent, iodide reduces `Cu^(2+)` to `Cu^(+)` ion. Chloride is a weak reducing agent. It does not reduce `Cu^(2+)` ion.
`2Cu^(2+)+4KIrarr Cu_(2)I_(2)+I_(2)+4K^(+)`