Statement I: Acid strength increases in the order $\mathrm{HF}$ < $\mathrm{HCl}$ < $\mathrm{HBr}$ < $\mathrm{HI}$. Statement II: As the size of the elements $\mathrm{F}$, $\mathrm{Cl}$, $\mathrm{Br}$, $\mathrm{I}$ increases down the group, the bond strength of $\mathrm{HF}$, $\mathrm{HBr}$ and $\mathrm{HI}$ decreases and so the acid strength increases. In the light of the above statements, choose the correct answer from the options given below:

Solution & Explanation

\textbf{Answer:} (C) Both Statement I and Statement II are true \textbf{Solution:} Down the halogen group, atomic size increases so the H-X bond lengthens and its bond dissociation enthalpy decreases ($\mathrm{H}-\mathrm{F}$ > $\mathrm{H}-\mathrm{Cl}$ > $\mathrm{H}-\mathrm{Br}$ > $\mathrm{H}-\mathrm{I}$). Weaker H-X bonds release $\mathrm{H}{}^{+}$ more easily, so acid strength increases $\mathrm{HF}$ < $\mathrm{HCl}$ < $\mathrm{HBr}$ < $\mathrm{HI}$. Both statements are correct.