JEE Advanced 2025 — Paper 2 — CHEM-II solution

JEE Advanced2025Paper 2CHEM-II

The compound(s) with P-H bond(s) is(are)

A
H $_{3}$ PO $_{4}$
B
H $_{3}$ PO $_{3}$
C
H $_{4}$ P $_{2}$ O $_{7}$
D
H $_{3}$ PO $_{2}$

Solution

The number of P-H bonds in an oxoacid of phosphorus equals (number of H) minus (number of OH groups), since only H atoms not attached to O are bonded directly to P.

H $_{3}$ PO $_{4}$ (orthophosphoric acid): structure (HO) $_{3}$ P=O, all three H are on oxygen. No P-H bond.

H $_{3}$ PO $_{3}$ (phosphorous acid): structure (HO) $_{2}$ P(H)=O, one H is bonded directly to P. Has one P-H bond.

H $_{4}$ P $_{2}$ O $_{7}$ (pyrophosphoric acid): two PO $_{4}$ tetrahedra sharing an oxygen, all four H on terminal OH groups. No P-H bond.

H $_{3}$ PO $_{2}$ (hypophosphorous acid): structure (HO)P(H) $_{2}$ =O, two H are bonded directly to P. Has two P-H bonds.

$∴$ Correct options are (B) and (D).

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