Question

Complete the following statements by selecting the correct alternative from the choices given:
In the complexes ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$ and ${\left[Pt\right(en\left){\left(H_{2}O\right)}_2\left(N{O}_2\right)\right(Cl\left)\right]}^{2+}$ the respective oxidation numbers of central metal atoms are:

• A. $+3$ and $+4$
• B. $+6$ and $+4$
• C. $+6$ and $+3$
• D. $+3$ and $+3$

Answer 1

Answer: (A)

$+3$ and $+4$

In the complexes ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$ and ${\left[Pt\right(en\left){\left(H_{2}O\right)}_2{NO}_2\right(Cl\left)\right]}^{2+}$ the respective oxidation numbers of central metal atoms are +3 and +4.

In ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$, the cyano ligand has -1 oxidation number. Six cyano ligands contribute -6 to the oxidation number. The complex ion has a net charge of -3. Hence, the oxidation number of Fe is +3.

In the complex, en and water ligands have 0 oxidation number and Cl ligand has -1 oxidation number and NO${}_2$ ligand has -1 oxidation number. The net charge of the complex ion is +2. Hence, the oxidation number of Pt is +4. ${\left[Pt\right(en\left){\left(H_{2}O\right)}_2\right({NO}_2\left)\right(Cl\left)\right]}^{2+}$