Q.Among the following the correct order of acidity is (NEET)

Step 1. Recall the general rule for oxoacid strength.

For a series of oxoacids of the same central atom, acid strength increases as the number of oxygen atoms bonded to the central atom (and hence the oxidation state of that atom) increases, because each additional oxygen withdraws electron density inductively and delocalises the negative charge over more atoms in the conjugate base, stabilising it and favouring ionisation.

Step 2. Apply this to the chlorine oxoacid series.

Hypochlorous acid HOCl (1 oxygen) is the weakest, followed by chlorous acid HClO2 (2 oxygens), then chloric acid HClO3 (3 oxygens), with perchloric acid HClO4 (4 oxygens) being the strongest — in fact perchloric acid is one of the strongest known simple acids.

Step 3. Note the inverse oxidising-power trend (for context). …

Apply the standard oxoacid-strength rule (more oxygens on the central atom → stronger acid, via better charge delocalisation …

Confusing the acidity trend with the oxidising-power trend, which runs in the opposite d …