DP Chemistry (first assessment 2025)
Question 22M.2.SL.TZ2.f(ii)
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.SL.TZ2.f(ii) |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Draw, Label | Question number | f(ii) | Adapted from | N/A |
f(ii).
[Maximum mark: 2]
22M.2.SL.TZ2.f(ii)
Draw and label an enthalpy level diagram for this reaction.
[2]
Markscheme
reactants at higher enthalpy than products ✔
ΔH/-99 «kJ» labelled on arrow from reactants to products
OR
activation energy/Ea labelled on arrow from reactant to top of energy profile ✔
Accept a double headed arrow between reactants and products labelled as ΔH for M2.
Examiners report
Most candidates drew correct energy profiles, consistent with the sign of the energy change calculated in the previous question. And again, only very weak candidate failed to get at least 1 mark for correct profiles.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.5—Catalysts increase the rate of reaction by providing an alternative reaction pathway with lower Ea. Sketch and explain energy profiles with and without catalysts for endothermic and exothermic reactions. Construct Maxwell–Boltzmann energy distribution curves to explain the effect of different values for Ea on the probability of successful collisions.