Question

The sum of oxidation number of the metals in the following species is:

(a)$K_3\left[Fe\right(CN{)}_6]$ (b)$K_3\left[Cr\right(C_2{O}_4{)}_3]$

(c)$\left[Ni\right(CN{)}_4{]}^{2-}$ (d)$N{a}_{2}Mo{O}_4$

(e)$Fe(CO{)}_5$ (f)$MgW{O}_4$

• A. 21
• B. 20
• C. 23
• D. 18

Answer 1

Answer: (B)

20

a) $K_3\left[Fe\right(CN{)}_6]$ Oxidation number is 1(+3)+x-6(-1) = 0,i.e x = 6-3 i.e +3

b) $K_3\left[Cr\right(C_2{O}_4{)}_3]$ Oxidation number is 3(+1)+x-3(-2) = 0,i.e x = 6-3 i.e +3

c) $\left[Ni\right(CN{)}_4{]}^{2-}$ Oxidation number is x-4+2 = 0,i.e x = 4-2 i.e +2

d) $N{a}_{2}Mo{O}_4$ Oxidation number is 2(+1)+ x -4(-2) = 0,i.e x = 8-2 i.e +6

e) $Fe(CO{)}_5$ oxidation state of Fe in $Fe(CO{)}_5$ is 0 because CO is a neutral ligand and does not contribute to charge so Fe is in its neutral state with oxidation number = 0

f)$MgW{O}_4$ Oxidation number is 1(+2)+ x - 4(-2) = 0,i.e x = 8-2 i.e +6. So the sum of oxidation staes is is 3+3+2+6+0+6 which is equals to 20

Hence option B is correct.