Question

Calculate the oxidation number of underlined elements in the following compounds:
$K\left[\underset{--}{Co}\right(C_2{O}_4{)}_2\left(N{H}_3{)}_2\right]$

• A. 2
• B. 3
• C. -2
• D. -3

Answer 1

The correct option is B 3

$K\left[\underset{--}{Co}\right(C_2{O}_4{)}_2\left(N{H}_3{)}_2\right]$
Charge on coordination sphere = -1
charge on $C_2{O}_4^{2-}=-2$
charge on $N{H}_3=0\because \text{it is a neutral molecule}$
Let x be oxidation state of Co
$\therefore x-4+0=-1$
$\therefore x=+3$