p Block Elements Part 3

Concept:Boiling point depends on intermolecular forces; hydrogen bonding raises boiling point dramatically.Melting point depends on packing and dispersion forces; larger molecules have stronger London forces in solid state.Explanation:For boiling point, as size increases from $\mathrm{HCl}$ to $\mathrm{HI}$, van der Waals forces increase, so boiling point increases.But $\mathrm{HF}$ has strong hydrogen bonding due to high electronegativity of fluorine, so its boiling point is highest.Thus increasing order of boiling point is $\mathrm{HCl} < \mathrm{HBr} < \mathrm{HI} < \mathrm{HF}$.For melting point, dispersion forces dominate in solid state.$\mathrm{HI}$ has the largest size and strongest London forces, giving the highest melting point.$\mathrm{HF}$ has hydrogen bonding but its melting point is lower than $\mathrm{HI}$ because HI's dispersion forces are stronger.So increasing order of melting point is $\mathrm{HCl} < \mathrm{HBr} < \mathrm{HF} < \mathrm{HI}$.Both Statement I and Statement II correctly represent these orders.Answer:Option D: Both Statement I and Statement II are true.