DP Chemistry (first assessment 2025)
Question 21M.2.HL.TZ2.b(iv)
| Date | May 2021 | Marks available | [Maximum mark: 3] | Reference code | 21M.2.HL.TZ2.b(iv) |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Sketch | Question number | b(iv) | Adapted from | N/A |
b(iv).
[Maximum mark: 3]
21M.2.HL.TZ2.b(iv)
Sketch an energy profile for the decomposition of calcium carbonate based on your answer to b(i), labelling the axes and activation energy, Ea.
[3]
Markscheme
endothermic sketch ✓
x-axis labelled “extent of reaction/progress of reaction/reaction coordinate/reaction pathway” AND y-axis labelled “potential energy/energy/enthalpy✓
activation energy/Ea ✓
Do not accept “time” for x-axis.
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.