Match the compounds given in Column I with the oxidation state of

cobalt has given in column II and assigns the correct code.

Column I

(Compound)

Column II

(Oxidation state of Co)

A.Co(NCS)(NH3)5(SO3)

1. +4

B.Co(NH3)4Cl2SO4

2.  +2

C.Na4Co(S2O3)3

3. 0

D.Co2(CO)8

4.  +3

Codes

          A          B          C           D

1.       2          3           4           1

2.       3          1           5           2

3.       5          4           3           2

4.       4          1           2           3

 Hint: Oxidation state of CO ligand is zero

Calculate the oxidation state of CO in different complexes as follows: 

A. Co(NCS)(NH3)5(SO3)

Let oxidation state of Co is x.

                  +2=-1+5×0+xx=+2+1=+3

B. Co(NH3)4Cl2SO4

Let oxidation state of Co is x

  x+4×0+2×(-1)=+2x-2=+2x=4

c. Na4Co(S2O3)3

 Let oxidation state of Co is x

X+3×(-2)=-4x-6=-4x=-4+6=+2

D.Co2(CO)8  

Let oxidation state of Co is x 

 x-8×0=0x=0

Hence, option 4th is the correct answer.