JEE Main · 2006 · 30 Apr 2006 · Offline · p-Block Elements

Each statement can be checked against known acid strengths. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_3$ is in fact stronger than ${\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_3$, and in water HCl is stronger than HF owing to HF's strong bond and hydrogen bonding, so those claims fail; $\mathrm{HCl}{\mathrm{O}}_4$ is stronger, not weaker, than $\mathrm{HCl}{\mathrm{O}}_3$ because its extra terminal oxygen delocalises the conjugate-base charge better. For the nitrogen oxoacids the same logic applies: the conjugate base $\mathrm{N}{\mathrm{O}}_3^{-}$ enjoys more extensive resonance than $\mathrm{N}{\mathrm{O}}_2^{-}$, so $\mathrm{HN}{\mathrm{O}}_3$ is indeed a stronger acid than $\mathrm{HN}{\mathrm{O}}_2$, the true statement.