Question

Oxidation number of $Cr$ in $Cr{O}_6$ is

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

Answer 1

Answer: (B)

The structure of $Cr{O}_5$ is

In $Cr{O}_5$ four oxygen atoms are present as peroxide (oxidation number $-1$ ) while the fifth is present as oxide (oxidation number $-2$ ).
Let the oxidation number of $Cr$ is $x$ in $Cr{O}_5$.
$\therefore x+4(-1)+1(-2)=0$
$x-4-2=0$
$x=+6$