Arrange the following in the increasing order of the property mentioned:(i) HOCl, HClO2, HClO3, HClO4 (acidic strength)(ii) MF, MCl, MBr, MI (ionic character)(iii) HF, HCl, HBr, HI (thermal stability)

Answer:

(i) HOCl < HClO₂ < HClO₃ < HClO₄. As the oxidation state of Cl increases (+1 to +7), more O atoms withdraw electrons and the conjugate anion is better stabilised by resonance, so acidity increases.

(ii) MI < MBr < MCl < MF. Ionic character increases with the electronegativity of the halogen and with decreasing size (less polarisable) of the halide ion; F is the most electronegative.

(iii) HI < HBr < HCl < HF. As the size of the halogen increases down the group, the H–X bond becomes longer and weaker (lower bond dissociation enthalpy), so thermal stability decreases from HF to HI.