Question

Assertion :Oxidation number of chromium in $Cr{O}_5$ is $+6$. Reason: Oxidation number of each oxygen atom is $-1.5$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

Generally, oxidation number of each oxygen atom is $-2$.
But if there is a peroxo linkage, then the oxidation number of oxygen becomes $-1$.
From the structure, we can see that $Cr{O}_5$ has a peroxy linkage.
Therefore, $x+4(-1)-2=0$
or, $x=+6$
Oxidation number of chromium in $Cr{O}_5$ is $+6$.
Thus, assertion is correct but reason is incorrect.