Chromium pentoxide, $CrO X_{5}$ , has chromium in its highest oxidation state, $+ 6$ , and contains peroxide linkages. The number of oxygen atoms with oxidation number $- 1$ is

Answer: C

Let

p

be the number of peroxide O (

- 1

). Then

- p - 2 (5 - p) = - 6

gives

p = 4

. So four O atoms are

- 1

(two

O X_{2} X^{2 -}

units) and one is

- 2

. Taking

p = 5

would give Cr as

+ 5