Question

The oxidation number of $Cr$ in $Cr{O}_5$ is:

• A. $+10$
• B. $+8$
• C. $+6$
• D. $+4$

Answer 1

The correct option is C $+6$

In $Cr{O}_5$, one oxygen is attached to Cr through the double bond. It has oxidation number $-2$. Four oxygen atoms are attached to Cr atom through a single bond. Each of these oxygen has an oxidation number $-1$.

Let $x$ be the oxidation number of chromium. The sum of all the oxidation numbers is zero.

Hence, $x-2+4(-1)=0$ and $x=6$.

Thus, the oxidation number of chromium in $Cr{O}_5$ is $+6$.

The structure of $Cr{O}_5$ is shown above.