Question

In the compound k[co(c2o4)2(h2o)2] (where c2o42– = oxalate) the oxidation number and coordination number of cobalt are, respectively

Answer 1

Answer:

Oxidation number: 3+

Coordination number: 4

Explanation:

In the compound K[Co(C₂O₄)₂(H₂O)₂] (where C₂O₄²⁻ = oxalate) the oxidation number and coordination number of Cobalt are, respectively?

The sum of the oxidation numbers and charges of the species forming the complex is equal to the overall charge, in this case, zero.

K + Co + 2 . C₂O₄²⁻ + 2 . H₂O = 0

+1 + Co + 2 . (2-) + 2 . 0 = 0

Co = 3+

The coordination number is the number of ligands attached to the central atom. 2 oxalates and 2 water molecules are attached to the cobalt atom, so the coordination number is 2 +2 = 4.

Answer 2

Let's Assign Symbols to molecules like,

                    C₂O₄  =  X
and 
                    H₂O   =  Y
Then,
                                K [ Co (X)₂ (Y)₂ ]

As, Potassium (K) has a O.N  =  +1

To neutralize, the coordination sphere must have -1 oxidation number.
So,
                                    [ Co (X)₂ (Y)₂ ]  =  -1
As,
           O.N of X  = -2
Then 
       O.N of (X)₂  =  -4

Also,
O.N of H₂O is zero as it is neutral, So,

                                    [Co - 4 + 0 ]  =  -1
Or,
                                    Co  =  -1 + 4

                                    Co  =  +3

Result:
          Oxidation Number of Coordination Sphere is -1 and Oxidation Number of Cu is +3.