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JEE Advanced 2018 Paper 1 · Chemistry · s-Block, p-Block Elements and Hydrogen · easy

(s) about oxoacids of phosphorus.

One or more options correct

Select the correct statement(s) about oxoacids of phosphorus.
  1. A. H3PO3\mathrm{H_3PO_3} is dibasic because it contains two P-OH groups and one P-H bond.
  2. B. Pyrophosphoric acid, H4P2O7\mathrm{H_4P_2O_7}, contains four P-OH groups and one P-O-P linkage.
  3. C. H3PO2\mathrm{H_3PO_2} contains two P-OH groups and one P-H bond.
  4. D. H3PO4\mathrm{H_3PO_4} acts as a reducing agent towards Ag+\mathrm{Ag^+} because of its P-H bonds.
Show answer and solution

Answer: A, B

Structures: H3PO3\mathrm{H_3PO_3} is HP(O)(OH)2\mathrm{HP(O)(OH)_2}, with two ionisable P-OH hydrogens and one non-ionisable P-H, so it is dibasic and A is true. Pyrophosphoric acid is (HO)2P(O)−O−P(O)(OH)2\mathrm{(HO)_2P(O)-O-P(O)(OH)_2}, with four P-OH groups and one bridging oxygen, so B is true. Hypophosphorous acid is H2P(O)(OH)\mathrm{H_2P(O)(OH)}, with only one P-OH and two P-H bonds; it is monobasic, so C is false. Orthophosphoric acid (HO)3P=O\mathrm{(HO)_3P=O} has no P-H bond and phosphorus is already in the +5 state, so it cannot act as a reductant and D is false. The reducing action in H3PO3 and H3PO2 comes from their P-H bonds.
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Original question written in the JEE Advanced 2018 Paper 1 pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake