Question

The stability constants of the complexes formed by a metal ion $\left(M^{2+}\right)$ with $N{H}_3,C{N}^{-},H_{2}O$ and $en$ are of the order ${10}^{11},{10}^{27},{10}^{15}$ and ${10}^8$ respectively. Then:

• A. $en$ is the strongest ligand
• B. $C{N}^{-}$ is the strongest ligand
• C. these values cannot predict the strength of the ligend
• D. all ligands are equally strong

Answer 1

The correct option is B $C{N}^{-}$ is the strongest ligand

The stability constant for the complex $\left[M\right(CN{)}_6{]}^{4-}$ is maximum (${10}^{27}$). Hence, cyanide ion is the strongest ligand. For monodentate ligands, higher is the value of stability constant, greater is the ligand strength.