Arrange `HOCl, HClO_(2), HClO_(3)` and `HClO_(4)` in order of (i) acidic strength and (ii) oxidising power. Give reason.

Explanation

Acidic strength: `HOCl lt HClO_(2) lt HClO_(3) lt HClO_(4)`


Greater is the number of resonance hybrids greater is the resonance stabilisation energy released and hence greater is the stability of oxoanion formed.
As the stability of oxoanion (conjugate base) formed after the removal of a proton increases, the acid strength increase in the same order.
Stability of conjugate base:
`CiO^(Theta) lt ClO_(2)^(Theta) lt ClO_(3)^(Theta) lt ClO_(4)^(Theta)`
Acidic strength : `HOCl lt HClO_(2) lt HCIO_(3) lt HClO_(4)`
(ii) Oxidising power: `HOCl gt HClO_(2) gt HCIO_(3) gt HClO_(4)`
As the stability of oxoanion increases, its tendency to decompose to give `O_(2)` decreases and hence its oxidising power decreases.
Stability of oxoanion:
`CiO^(Theta) lt ClO_(2)^(Theta) lt ClO_(3)^(Theta) lt ClO_(4)^(Theta)`
Oxidising power: `HOCl gt HClO_(2) gt HCIO_(3) gt HClO_(4)` .