Question

Assertion : $HClO_4$ is a stronger acid than $HClO_3$.
Reason : Oxidation state of chlorine in $HClO_4$ is $+7$ and in $HClO_3$ is $+5$.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

$HClO _{4}$ is stronger than $HClO _{3}$. The oxidation number of $Cl$ in $HClO _{4}$ is $+7$ and in $HClO _{3}$ is $+5$. The acid strength of oxyacid of the same halogen increases with the increase in oxidation number of halogen.
$HOCl < HClO _{2}< HClO _{3}< HClO _{4}$
It can also be explained on the basis of presence of oxygen atoms. The acidity of acid increase with increase in number of oxygen atoms as the electronegative (powerful electron withdrawing group) weakens the - $OH$ bond and thus proton can be donated easily.