Question

What is the oxidation state of Cr in $Cr{O}_5$ ?

• A. 10
• B. 5
• C. 6
• D. 3

Answer 1

Answer: (C)

In the structure of $Cr{O}_5$, it has four $O$ atoms as peroxide which have oxidation number $=-1$ and one $O$ as oxide (double bonded $O$ ) atom with oxidation number $=-2$.
Let the oxidation number of $Cr$ is $x$.
Then, $x+4\times (-1)+1\times (-2)=0$
or $x=+6$
The oxidation number of $Cr$ in $Cr{O}_5$ is $+6$.