1.

Ammonia forms the complex [Cu(NH_(3))_(4)]^(2+) will copper ions in alkaline solution but not in acidic solution. The reason for this is

Answer»

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

Solution :`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.


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