⇒ In oxoacids, acidic strength increases with increase in number of double bonded oxygen atoms because of greater resonance stabilization of conjugate base. Hence HClO4 is more acidic than HClO.
⇒ Central atom in both HClO4 and HClO is sp3 hybridized. ⇒ HClO4+H2O→ClO4−+H3O+ This equilibrium remain shifted in forward direction hence ClO4− is weaker base than H2O. Because such equilibrium remain shifted towards weaker acid or weaker base side. ⇒Cl2+H2O→HCl+HOCl