JEE Main · 2023 · Shift-ImediumPB12-058

Reaction of thionyl chloride with white phosphorus forms a compound [A], which on hydrolysis gives [B], a dibasic acid.…

p-Block Elements (Class 12) · Class 12 · JEE Main Previous Year Question

Question

Reaction of thionyl chloride with white phosphorus forms a compound [A], which on hydrolysis gives [B], a dibasic acid. [A] and [B] are respectively

Options
  1. a

    P4O6\mathrm{P_4O_6} and H3PO3\mathrm{H_3PO_3}

  2. b

    PCl3\mathrm{PCl_3} and H3PO3\mathrm{H_3PO_3}

  3. c

    PCl5\mathrm{PCl_5} and H3PO4\mathrm{H_3PO_4}

  4. d

    POCl3\mathrm{POCl_3} and H3PO4\mathrm{H_3PO_4}

Correct Answerb

PCl3\mathrm{PCl_3} and H3PO3\mathrm{H_3PO_3}

Detailed Solution

Strategy: Analyze the reaction sequence involving phosphorus and thionyl chloride.

Step 1: Identifying A The reaction of white phosphorus (\ceP4)(\ce{P4}) with thionyl chloride yields phosphorus trichloride: \ceP4+8SOCl24PCl3+4SO2+2S2Cl2\ce{P4 + 8SOCl2 \to 4PCl3 + 4SO2 + 2S2Cl2} Thus, A is \cePCl3\ce{PCl3}.

Step 2: Identifying B The hydrolysis of \cePCl3\ce{PCl3} yields phosphorous acid: \cePCl3+3H2OH3PO3+3HCl\ce{PCl3 + 3H2O \to H3PO3 + 3HCl} B is \ceH3PO3\ce{H3PO3}. It is a dibasic acid because it contains two ionisable \cePOH\ce{P-OH} protons (its structure is \ceHP(=O)(OH)2\ce{H-P(=O)(OH)2}).

Answer: (Option) [b] \cePCl3 and \ceH3PO3\boxed{\text{Answer: (Option) [b] $\ce{PCl3}$ and $\ce{H3PO3}$}}

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