JEE Advanced 2021 Paper 2 Q06 Chemistry Inorganic Chemistry p-Block Elements (Groups 15-18) Medium

JEE Advanced 2021 Paper 2 · Q06 · p-Block Elements (Groups 15-18)

The correct statement(s) related to oxoacids of phosphorous is(are)

  1. A. Upon heating, H$_3$PO$_3$ undergoes disproportionation reaction to produce H$_3$PO$_4$ and PH$_3$.
  2. B. While H$_3$PO$_3$ can act as reducing agent, H$_3$PO$_4$ cannot.
  3. C. H$_3$PO$_3$ is a monobasic acid.
  4. D. The H atom of P–H bond in H$_3$PO$_3$ is not ionizable in water.
JEE Advanced multi-correct — pick every correct option, then check.
Reveal answer + step-by-step solution

Correct answer:A, B, D

Solution

(A) On heating, H$_3$PO$_3$ disproportionates: 4 H$_3$PO$_3$ $\xrightarrow{\Delta}$ 3 H$_3$PO$_4$ + PH$_3$. CORRECT.

(B) H$_3$PO$_3$ has a P-H bond which makes it a reducing agent. H$_3$PO$_4$ has no P-H bond (all three H are on O), so it is not a reducing agent. CORRECT.

(C) H$_3$PO$_3$ has two P-OH groups and one P-H bond. Only the OH hydrogens are ionizable, so it is DIBASIC, not monobasic. WRONG.

(D) The H on P (P-H bond) is non-ionizable because it is not bonded to a strongly electronegative atom; only OH hydrogens ionize. CORRECT.

Hence A, B, D are correct.

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