Question

Ammonia forms the complex ion $\left[Cu\right(N{H}_3{)}_4{]}^{+2}$ with copper ions in alkaline solutions but not in acidic solutions. What is the reason for it?

• A. In acidic solutions, hydration protects copper ion
• B. In acidic solution, protons co – ordinate with ammonia molecules forming $N{H}_4^{+}$ ions and $N{H}_3$ molecules are not available
• C. In alkaline solutions insoluble $Cu\left(O{H}_2\right)$ is precipitated which is soluble in excess of an alkali
• D. Copper hydroxide is an amphoteric substance

Answer 1

The correct option is B

In acidic solution, protons co – ordinate with ammonia molecules forming $N{H}_4^{+}$ ions and $N{H}_3$ molecules are not available

$\stackrel{..}{N}{H}_3+H^{+}\to N{H}_4^{+}$