Question 22M.2.hl.TZ1.b(ii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.hl.TZ1.b(ii) |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | b(ii) | Adapted from | N/A |
Ammonia is produced by the Haber–Bosch process which involves the equilibrium:
N2 (g) + 3 H2 (g) 2 NH3 (g)
The percentage of ammonia at equilibrium under various conditions is shown:
[The Haber Bosch Process [graph] Available at: https://commons.wikimedia.org/wiki/File:Ammonia_yield.png
[Accessed: 16/07/2022].]
One factor affecting the position of equilibrium is the enthalpy change of the reaction.
Outline why the value obtained in (b)(i) might differ from a value calculated using ΔHf data.
[1]
«N-H» bond enthalpy is an average «and may not be the precise value in NH3» ✔
Accept ΔHf data are more accurate / are not average values.
Outlining why ΔHrxn based on BE values differ due to being average compared to using ΔHf values was generally done well.
