DP Chemistry (last assessment 2024)
Question 21N.2.hl.TZ0.c(iii)
| Date | November 2021 | Marks available | [Maximum mark: 2] | Reference code | 21N.2.hl.TZ0.c(iii) |
| Level | hl | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate | Question number | c(iii) | Adapted from | N/A |
c(iii).
[Maximum mark: 2]
21N.2.hl.TZ0.c(iii)
White phosphorus is an allotrope of phosphorus and exists as P4.
An equilibrium exists between PCl3 and PCl5.
PCl3 (g) + Cl2 (g) PCl5 (g)
Calculate the Gibbs free energy change (ΔG), in kJ mol−1, for this reaction at 25 °C. Use section 1 of the data booklet.
If you did not obtain an answer in c(i) or c(ii) use −87.6 kJ mol−1 and −150.5 J mol−1 K−1 respectively, but these are not the correct answers.
[2]
Markscheme
«ΔS =» –0.1702 «kJ mol–1 K–1»
OR
298 «K» ✔
«ΔG = –92.5 kJ mol–1 – (298 K × –0.1702 kJ mol–1 K–1) =» –41.8 «kJ mol–1» ✔
Award [2] for correct final answer.
If –87.6 and -150.5 are used then –42.8.
