JEE Main · 2021 · 18 Mar 2021 · Shift 1 · p-Block Elements

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The number of ionisable hydrogens present in the product obtained from a reaction of phosphorus trichloride and phosphonic acid is:
  1. (A)1
  2. (B)3
  3. (C)0
  4. (D)2✓ Correct

Answer: (D)

Solution

Phosphonic acid is H₃PO₃ (or better written as HPO(OH)₂). When PCl₃ reacts with H₃PO₃, it forms pyrophosphonic acid H₄P₂O₅. This compound has 2 ionizable hydrogens (the two P-OH groups). The P-H hydrogens are not acidic/ionizable. Therefore, the answer is 2.

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Single correct option

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