Question

Aqueous Copper sulphate reacts with aq ammonium hydroxide to form cupric hydroxide and ammonium sulphate. followed and balance ​

Answer 1

Answer:

This is a good illustration of Le Chatelier's principle and of complex ion formation.

The copper ion in the aqueous solution of exists mostly as [Cu(H2O)6]2+. This complex ion imparts a characteristic pale blue color to the solution. Since ammonia is a weak base, when it is added, hydroxide ion forms:

NH3(aq) + H2O(l) <==> NH4+(aq) + OH-(aq); pKb = 9.25 (1)

The hydroxide ion reacts with the hexa-aqua-copper(II) ion to form the insoluble compound, copper(II) hydroxide 2hydrate:

[Cu(H2O)6]2+(aq) + 2 OH-(aq) <==> Cu(OH)2 * 2 H2O(s) + 2 H2O

In a simple notation :

Cu2+(aq) + 2 OH-(aq) <==> Cu(OH)2 (s) ( Ksp = 2.2 X 10-20 )

Adding more ammonia results in the formation of a soluble deep blue complex copper ammonia ion:

[Cu(H2O)6]2+(aq) + 4 NH3 (aq) <==> [Cu(NH3)4(H2O)2]2+(aq) + 4 H2O(l) ,with Kc = 1.2 X 1013

Cu2+(aq) + 4 NH3 (aq) <==> Cu(NH3)4 2+( aq)