DP Chemistry (first assessment 2025)
Question 22M.2.SL.TZ2.b(i)
| Date | May 2022 | Marks available | [Maximum mark: 3] | Reference code | 22M.2.SL.TZ2.b(i) |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Sketch | Question number | b(i) | Adapted from | N/A |
b(i).
[Maximum mark: 3]
22M.2.SL.TZ2.b(i)
On the axes, sketch Maxwell–Boltzmann energy distribution curves for the reacting species at two temperatures T1 and T2, where T2 > T1.
[3]
Markscheme
both axes correctly labelled ✔
peak of T2 curve lower AND to the right of T1 curve ✔
lines begin at origin AND correct shape of curves AND T2 must finish above T1 ✔
Accept “probability «density» / number of particles / N / fraction” on y-axis.
Accept “kinetic E/KE/Ek” but not just “Energy/E” on x-axis.
Examiners report
Few got the 3 marks for this standard question (average mark 1.7), the most common error being incomplete/incorrect labelling of axes, curves beginning above 0 on y-axis or inverted curves.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.4—Activation energy, Ea, is the minimum energy that colliding particles need for a successful collision leading to a reaction. Construct Maxwell–Boltzmann energy distribution curves to explain the effect of temperature on the probability of successful collisions.