Question 22M.2.sl.TZ2.3b(i)
| Date | May 2022 | Marks available | [Maximum mark: 3] | Reference code | 22M.2.sl.TZ2.3b(i) |
| Level | sl | Paper | 2 | Time zone | TZ2 |
| Command term | Label, Sketch | Question number | b(i) | Adapted from | N/A |
Sulfur trioxide is produced from sulfur dioxide.
2SO2 (g) + O2 (g) 2SO3 (g) ΔH = −196 kJ mol−1
The reaction between sulfur dioxide and oxygen can be carried out at different temperatures.
On the axes, sketch Maxwell–Boltzmann energy distribution curves for the reacting species at two temperatures T1 and T2, where T2 > T1.
[3]
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.
The average mark scored for the Maxwell-Boltzmann distribution curves sketch was 1.5 out of 3 marks and the question had a strong correlation with the candidates who did well overall. The majority of candidates were familiar with the shapes of the curves. The most commonly lost mark was missing or incorrect labels on the axes. Sometimes candidates added the labels but did not specify “kinetic” energy for the x-axis. As for the curves, some candidates reversed the labels T1 and T2, some made the two curves meet at high energy or even cross, and some did not have the correct relationship between the peaks of T1 and T2.