Question

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

• A. + 3
• B. + 5
• C. + 10
• D. + 6

Answer 1

Answer: (D)

The structure of $Cr{O}_5$ is as

The structure shows that four oxygen atom in $Cr{O}_5$ are involve in the formation of peroxide linkage (OS of oxygen $=-1$ ) while one is present as oxide (OS of oxygen $=-2$ ). Therefore, $Cr{O}_5$
$\underset{\text{for Cr}}{x+1}\times \underset{\text{for O}}{(-2)}+\underset{\text{for (O-O)}}{4(-1)=0}$
$x-2-4=0$
$x=+6$