JEE Main 2018 · Chemistry · s-Block, p-Block Elements and Hydrogen · easy

The total number of ionisable (O-H, acidic) hydrogen atoms present in one molecule each of H3PO2, H3PO3, H3PO4 and H4P2O7 taken together is

Single correct option

The total number of ionisable (

\mathrm{O{-}H}

, acidic) hydrogen atoms present in one molecule each of

\mathrm{H_3PO_2}

\mathrm{H_3PO_3}

\mathrm{H_3PO_4}

and

\mathrm{H_4P_2O_7}

taken together is

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Answer: (C) $10$

Only hydrogens bonded to oxygen ionise; P-H hydrogens do not.

\mathrm{H_3PO_2}

(hypophosphorous acid) has

1

P-OH and two P-H: monobasic,

1

\mathrm{H_3PO_3}

has

2

P-OH and one P-H: dibasic,

2

\mathrm{H_3PO_4}

has

3

P-OH:

3

\mathrm{H_4P_2O_7}

(pyrophosphoric acid) has

4

P-OH groups:

4

. Total

=1+2+3+4=10

. Counting all hydrogens would give

13

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