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JEE Main 2022 · Chemistry · s-Block, p-Block Elements and Hydrogen · medium

The total number of P - OH bonds present in one molecule each of orthophosphoric acid, phosphorous acid, hypophosphorous acid and pyrophosphoric acid…

Numerical answer

The total number of P ⁣− ⁣OH\mathrm{P\!-\!OH} bonds present in one molecule each of orthophosphoric acid, phosphorous acid, hypophosphorous acid and pyrophosphoric acid (H4P2O7\mathrm{H_4P_2O_7}) taken together is
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Answer: 10

Count the ionisable (P-bonded OH) hydrogens, which equal the basicity. H3PO4\mathrm{H_3PO_4} has three P-OH groups. H3PO3\mathrm{H_3PO_3}, HPO(OH)2\mathrm{HPO(OH)_2}, has two P-OH and one direct P-H bond. H3PO2\mathrm{H_3PO_2}, H2PO(OH)\mathrm{H_2PO(OH)}, has one P-OH and two P-H bonds. H4P2O7\mathrm{H_4P_2O_7}, (HO)2OP−O−PO(OH)2\mathrm{(HO)_2OP-O-PO(OH)_2}, has four P-OH groups plus a P-O-P bridge. Total =3+2+1+4=10=3+2+1+4=10.
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