Question

Predict the order of Acidity-
HClO4, HClO3, HClO2, HOCl
Please mention reason.
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Answer 1

First of all the acidity of a compound is directly proportional to the oxidation number of the compound .

This means that we can have two possible outcomes :

⏩ The compound with the highest oxidation number is the most acidic .

⏩ The compound with the lowest oxidation number is the least acidic .

Given to us :

HClO₄ , HClO₃ , HClO₂ , HOCl .

These compounds share something in common .

Yes , the hydrogen ion is common in all the compounds .

So let us reduce the compounds to the following :

ClO⁴⁻ , ClO³⁻ , ClO²⁻ , ClO⁻ with which hydrogen reacts to make the following compounds .

Again we see that chlorine is common in every compound and hence we need to distinguish on the basis of oxygen which is left with us .

Now we know that chlorine is more electronegative than oxygen and hence the oxidation state of oxygen having bond with chlorine will always be positive .

Thus the oxidation state of the compound will depend directly on the number of oxygen atoms .

In simple words :

The more the oxygen , the more will the oxidation number and hence the more will be the acidity .

So the most acidic compound will be HClO⁴- , then HClO³- and so on ..

ANSWER :

HClO₄ > HClO₃ > HClO₂ > HOCl

Answer 2

your correct order is

HClOHClO4, HClO3, HClO2, HOCl