Q. Which of the following correctly ranks species by increasing acidity in aqueous solution?
✅ Correct Answer: (A)
NH3 < H2O < HF
Explanation: In water, ammonia (NH3) is the weakest acid among these (pKa of NH4+ is about 9.25, so NH3 is very weak acid), water is intermediate (pKa ~15.7), and HF is stronger (pKa ~3.2) — so acidity increases NH3 < H2O < HF. The other options list incorrect orderings.
Explanation by: Sikhar Chaudhary
In water, ammonia (NH3) is the weakest acid among these (pKa of NH4+ is about 9.25, so NH3 is very weak acid), water is intermediate (pKa ~15.7), and HF is stronger (pKa ~3.2) — so acidity increases NH3 < H2O < HF. The other options list incorrect orderings.