Question

Ammonia forms the complex ion $\left[Cu\right(N{H}_3{)}_4{]}^{2+}$ with copper ions in the alkaline solution because:

• A. in acidic solutions, protons coordinate with ammonia molecules.
• B. in acidic solutions, hydration protects copper ions.
• C. in alkaline solutions, insoluble $Cu(OH{)}_2$ is precipitated which is soluble in excess of any alkali.
• D. copper hydroxide is an atmospheric substance.

Answer 1

Answer: (A)

in acidic solutions, protons coordinate with ammonia molecules.

In acidic solutions $N{H}_3$ forms a bond with $H^{+}$ to form $N{H}_4^{+}$which does not have a lone pair on Nitrogen atom and hence cannot act as a ligand . The reaction is $N{H}_3+H^{+}\to N{H}_4^{+}$ .