Question

Copper sulphate solution forms blue coloured complex with excess of ammonia. Its formula is:

• A. $\left[Cu\right(N{H}_3{)}_4{]}^{+3}$
• B. $\left[Cu\right(N{H}_3{)}_4{]}^{+2}$
• C. $\left[Cu\right(N{H}_4{)}_3{]}^{+2}$
• D. $\left[Cu\right(N{H}_4{)}_3{]}^{+3}$

Answer 1

Answer: (B)

$\left[Cu\right(N{H}_3{)}_4{]}^{+2}$

Since, the ammonia has stonger ligand bonds than water with $C{u}^{2+}$. Hence, it can then forms a blue coloured solution of complex salt.

$Cu\left(S{O}_4\right).5H_{2}O+4N{H}_{4}OH\to Cu(N{H}_3{)}_{4}S{O}_4.H_{2}O+8H_{2}O$

$C{u}^{2+}+4N{H}_3\to \left[Cu\right(N{H}_3{)}_4{]}^{2+}$