JEE Advanced · 2020 · 27 Sep 2020 · Paper 1 · p-Block Elements

1. (A)The hypochlorite ion is the strongest conjugate base.✓ Correct
2. (B)The molecular shape of only chlorate ion is influenced by the lone pair of electrons of Cl.✓ Correct
3. (C)The hypochlorite and chlorate ions disproportionate to give rise to identical set of ions.
4. (D)The hypochlorite ion oxidizes the sulfite ion.✓ Correct

Answer: (A), (B), (D)

Solution

(A) Acidic strength order: $\mathrm{HClO}<\mathrm{HClO}{}_3<\mathrm{HClO}{}_4$. Therefore, conjugate base strength order: $\mathrm{ClO}{}^{-}>\mathrm{ClO}{}_3{}^{-}>\mathrm{ClO}{}_4{}^{-}$. Correct.

(B) $\mathrm{ClO}{}^{-}$ is linear (no effect of lone pair), $\mathrm{ClO}{}_3{}^{-}$ is trigonal pyramidal (lone pair affects shape), $\mathrm{ClO}{}_4{}^{-}$ is tetrahedral (no lone pair effect due to resonance). Correct.

(C) Disproportionation reactions:

• $3\mathrm{ClO}{}^{-}\to 2\mathrm{Cl}{}^{-}+\mathrm{ClO}{}_3{}^{-}$
• $4\mathrm{ClO}{}_3{}^{-}\to 3\mathrm{ClO}{}_4{}^{-}+\mathrm{Cl}{}^{-}$

They produce different sets of ions. Incorrect.

(D) $\mathrm{ClO}{}^{-}+\mathrm{SO}{}_3{}^{2-}\to \mathrm{SO}{}_4{}^{2-}+\mathrm{Cl}{}^{-}$. Hypochlorite oxidizes sulfite to sulfate. Correct.

JEE Advanced · 2020 · 27 Sep 2020 · Paper 1 · One or more correct options