JEE Main · 2021 · Shift-IImediumRDX-078

The exact volumes of 1 M NaOH solution required to neutralise 50 mL of 1\ M\ H3PO3 solution and 100 mL of 2\ M\ H3PO2…

Redox Reactions · Class 11 · JEE Main Previous Year Question

Question

The exact volumes of 1 M NaOH solution required to neutralise 50 mL of 1 M H3PO31\ \mathrm{M}\ \mathrm{H_3PO_3} solution and 100 mL of 2 M H3PO22\ \mathrm{M}\ \mathrm{H_3PO_2} solution, respectively, are:

Options
  1. a

    100 mL and 100 mL

  2. b

    100 mL and 50 mL

  3. c

    100 mL and 200 mL

  4. d

    50 mL and 50 mL

Correct Answerc

100 mL and 200 mL

Detailed Solution

H3PO3\mathrm{H_3PO_3} (phosphorous acid): Structure HPO(OH)2\mathrm{HPO(OH)_2} — 2 ionisable OH groups → basicity = 2 nNaOH=2×(1×0.05)=0.1 molV=100 mLn_{\mathrm{NaOH}} = 2 \times (1 \times 0.05) = 0.1\ \mathrm{mol} \Rightarrow V = 100\ \mathrm{mL}

H3PO2\mathrm{H_3PO_2} (hypophosphorous acid): Structure H2PO(OH)\mathrm{H_2PO(OH)} — 1 ionisable OH group → basicity = 1 nNaOH=1×(2×0.1)=0.2 molV=200 mLn_{\mathrm{NaOH}} = 1 \times (2 \times 0.1) = 0.2\ \mathrm{mol} \Rightarrow V = 200\ \mathrm{mL}

Answer: Option (3) — 100 mL and 200 mL

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