alleryAmong NH₃, PH₃, H₂O, H₂S — most acidic:
AH₂S (largest atom, weakest E-H bond → most acidic; pKa ~7)
BNH₃
CPH₃
DRandom
Answer & Solution
Correct answer: A. H₂S (largest atom, weakest E-H bond → most acidic; pKa ~7)
**Acidity in main group:** weaker H-E bond and larger E favors acidity.
H₂S pKa ≈ 7. NH₃ pKa ≈ 38 (very weak acid).
PH₃ ≈ 27. H₂O = 15.7. So H₂S most acidic.
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