Question

The oxidation number of $CrinCr{O}_5$ is

• A. +3
• B. + 5
• C. + 6
• D. 0

Answer 1

Answer: (C)

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 $+6$.