The unique behaviour of CU, having a positive `E^(@)` (reduction potential) accounts for its inability to liberate `H_(2)` from acids,. Only oxidising acids (nitric acid and hot concentrated sulphuric acid) react with Cu. The high energy of transform Cu(s) to `Cu^(2+)(aq.)` is not balanced by its hydration enthalpy.
On the other hand, All Cu(II) halides are known except iodide. in this case, `Cu^(2+)` oxidises `I^(-)` to `I_(2)`:
`2Cu^(2+)+4I^(-) to 2CuI(s)+I_(2)`
However, copper (I) compounds are unstable in aqueous solution annd undergo disproportionation.
`2Cu^(+)(aq.)toCu^(2+)(aq.)+Cu`
The stability of `Cu^(2+)(aq.)` rather than `Cu^(+)(aq)` is due to the much more negative `Delta_(Hyd)` of `Cu^(2+)(aq.)` than `Cu^(+)(aq.)`
Q. Consider the following transformation:
`CuSO_(4)(aq.)+KI(excess)to`product
Select the correct statement:

Options

A. Product contains `[Cu(H_(2)O_(4))]^(2+)` ion.
B. Presence of brown colouration in product is due to `I_(3)^(-)` ion
C. Oxidation state of sulphur in reactant and product is different
D. white ppt. of `CuI_(2)` is observed in product

Answer

B

Explanation

`CuSO_(4)(aq.)+underset("Excess")(3I^(-)(aq.))tounderset("White")(CuIdarr)+underset("Brown colour")(I_(3)^(-)(aq.))+SO_(4)^(2-)(aq.)`