JEE Advanced 2024 Paper 1 · Chemistry · s-Block, p-Block Elements and Hydrogen · medium

Regarding the oxoacids, oxides and halides of the group 15 elements and boron trihalides, choose the correct statement(s).

One or more options correct

A. $\mathrm{H_3PO_3}$ is a dibasic acid and its anion $\mathrm{H_2PO_3^-}$ cannot be neutralised further by a base
B. In the solid state $\mathrm{N_2O_5}$ exists as $\mathrm{[NO_2]^+[NO_3]^-}$
C. In the solid state $\mathrm{PCl_5}$ exists as $\mathrm{[PCl_4]^+[PCl_6]^-}$
D. $\mathrm{BF_3}$ is a stronger Lewis acid than $\mathrm{BCl_3}$ because of the higher electronegativity of fluorine

Show answer and solution

Answer: B, C

\mathrm{H_3PO_3}

is dibasic, but its anion

\mathrm{H_2PO_3^-}

still has one ionisable P–OH hydrogen, so it can be neutralised again to

\mathrm{HPO_3^{2-}}

; the statement's second part is false, so A is incorrect. B: solid

\mathrm{N_2O_5}

is ionic, nitronium nitrate

\mathrm{[NO_2]^+[NO_3]^-}

; correct. C: solid

\mathrm{PCl_5}

has tetrahedral

\mathrm{PCl_4^+}

and octahedral

\mathrm{PCl_6^-}

; correct. D: the Lewis acidity order is

\mathrm{BF_3}<\mathrm{BCl_3}<\mathrm{BBr_3}

, because the

2p\pi

–

2p\pi

back-donation from F to B is strongest and reduces the electron deficiency of B in

\mathrm{BF_3}

; incorrect. Correct options: B and C.

Original question written in the JEE Advanced 2024 Paper 1 pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake