Question

The oxidation number of $Cr$ in $Cr{O}_5$ which has the following structure is:

• A. 4
• B. 5
• C. 6
• D. 3

Answer 1

Answer: (C)

6

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.