Question 19M.2.hl.TZ2.2f
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.hl.TZ2.2f |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Annotate, Outline | Question number | f | Adapted from | N/A |
The thermal decomposition of dinitrogen monoxide occurs according to the equation:
2N2O (g) → 2N2 (g) + O2 (g)
The reaction can be followed by measuring the change in total pressure, at constant temperature, with time.
The x-axis and y-axis are shown with arbitrary units.
The graph below shows the Maxwell–Boltzmann distribution of molecular energies at a particular temperature.
The rate at which dinitrogen monoxide decomposes is significantly increased by a metal oxide catalyst.
Annotate and use the graph to outline why a catalyst has this effect.
[2]
catalysed and uncatalysed Ea marked on graph AND with the catalysed being at lower energy [✔]
«for catalysed reaction» greater proportion of/more molecules have E ≥ Ea / E > Ea
OR
«for catalysed reaction» greater area under curve to the right of the Ea [✔]
Note: Accept “more molecules have the activation energy”.
The graph was generally well done, but in quite a few cases, candidates did not mention that increase of rate in the catalyzed reaction was due to E (particles) > Ea or did so too vaguely.
