Correct Answer: Option B

Explanation

When ammonia is added to a copper(II) nitrate solution, a pale blue precipitate of copper(II) hydroxide (Cu(OH)2) forms. The balanced equation for this reaction is

      Cu(NO\(_3\))\(_2\)  +  2NH\(_4\)OH→Cu(OH)2↓ +  2NH\(_4\)NO\(_3\)

Excess ammonia: When more ammonia is added, the precipitate dissolves and forms a deep blue solution of tetraammine copper(II) nitrate. The balanced equation for this reaction is   Cu(OH)2(s)+4NH3(aq)−⇀↽−[Cu(NH3)4]+2(aq)+2OH−(aq)

This happens because the addition of more ammonia causes the formation of a coordination complex cation of copper(II) bonded to four ammonia molecules. This shifts the solubility equilibrium of copper(II) hydroxide to the right, causing the precipitate to dissolve.

There is an explanation video available below.

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