According to Maxwell- Boltzmann distribution, the maximum in the curve between fraction of molecule (NE/NT) with a given kinetic energy (E) vs kinetic energy, gives
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Most probable kinetic energy.
At a given temperature the molecules of a gas have a spread of kinetic energies. The peak of the Maxwell–Boltzmann curve is the energy held by the largest fraction of molecules, the most probable kinetic energy. The activation energy lies far out in the right-hand tail, where only a small fraction of molecules reach it.
Why the other options are incorrect
Option (1) Average kinetic energy. — Incorrect. The curve is not symmetrical: it has a long tail towards high energies. So the average kinetic energy lies to the right of the peak, not at it.
Option (2) Kinetic energy possessed by half the molecules present. — Incorrect. The peak gives the energy held by the largest fraction of molecules, not by half of them. The energy that divides the molecules into two equal halves is a different point, to the right of the peak because of the long high-energy tail.
Option (4) Activation energy. — Incorrect. Only a small fraction of molecules have energy equal to or greater than the activation energy. So it is marked far out in the right-hand tail of the curve, not at the peak.
NCERT (2026-27 edition):
Temperature Dependence of the Rate of a Reaction – …
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| 31-05 S2 30-05 S2 12-05 S2 | – | – | 10-06 S1 | – |