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JEE Advanced 2025 Paper 2 · Chemistry · s-Block, p-Block Elements and Hydrogen · medium

Oxoacids and oxides of phosphorus is/are correct?

One or more options correct

Which of the following statements about oxoacids and oxides of phosphorus is/are correct?
  1. A. H3PO3\mathrm{H_3PO_3} is dibasic and on heating disproportionates into H3PO4\mathrm{H_3PO_4} and PH3\mathrm{PH_3}
  2. B. The molecule P4O10\mathrm{P_4O_{10}} contains six P−O−P\mathrm{P{-}O{-}P} bridges and four terminal P=O\mathrm{P{=}O} bonds
  3. C. H3PO2\mathrm{H_3PO_2} reduces aqueous AgNO3\mathrm{AgNO_3} to metallic silver
  4. D. All sixteen phosphorus-oxygen bonds in P4O10\mathrm{P_4O_{10}} have the same length
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Answer: A, B, C

(A) Correct. H3PO3\mathrm{H_3PO_3} has two P−OH\mathrm{P{-}OH} groups and one P−H\mathrm{P{-}H}, so it is dibasic; on heating 4H3PO3→3H3PO4+PH34\mathrm{H_3PO_3}\rightarrow3\mathrm{H_3PO_4}+\mathrm{PH_3} (P: +3→+5+3\rightarrow+5 and −3-3). (B) Correct. P4O10\mathrm{P_4O_{10}} is the P4O6\mathrm{P_4O_6} cage with six bridging oxygen atoms, each phosphorus also carrying one terminal oxygen as P=O\mathrm{P{=}O}. (C) Correct. H3PO2\mathrm{H_3PO_2} has two P−H\mathrm{P{-}H} bonds and is a strong reducing agent: 4Ag++H3PO2+2H2O→4Ag+H3PO4+4H+4\mathrm{Ag^+}+\mathrm{H_3PO_2}+2\mathrm{H_2O}\rightarrow4\mathrm{Ag}+\mathrm{H_3PO_4}+4\mathrm{H^+}. (D) Incorrect. Of the sixteen P−O\mathrm{P{-}O} bonds, twelve are bridging P−O\mathrm{P{-}O} (longer, about 160 pm160\ \mathrm{pm}) and four are terminal P=O\mathrm{P{=}O} (shorter, about 143 pm143\ \mathrm{pm}).
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