Ammonia forms the complex `[Cu(NH_3)_4]^(2+)` with copper ions in alkaline solution but not in acid solution. The reasons for it is:

Options

A. In alkline solution `Cu(OH)_(2)` is precipitated which is soluble in exces of alkali
B. Copper hydroxide is amphoteric substance
C. in acidic solution hydration protects `Cu^(2+)` ions.
D. In acidic solution protons are coordinated with ammonia molecules forming `NH_(4)+^(+)` ion.

Answer

D

Explanation

`Cu^(2+)(aq)+4NH_(3)overset(OH^(-)) hArr [Cu(NH_(3))_(4)]^(2+)`
`Cu^(2+)(aq)+4NH_(3) overset(OH^(+))hArr Cu^(2+)+4NH_(4)^(+)` (No complex formation)
As `NH_(3)` combines with `H^(+)` of acid and changes to `NH_(4)^(+)` which have no donor site.