DP Chemistry (first assessment 2025)
Question 22M.2.HL.TZ2.d(iv)
Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.HL.TZ2.d(iv) |
Level | HL | Paper | 2 | Time zone | TZ2 |
Command term | Calculate | Question number | d(iv) | Adapted from | N/A |
d(iv).
[Maximum mark: 2]
22M.2.HL.TZ2.d(iv)
Calculate the equilibrium constant, Kc, for this reaction at 298 K. Use your answer to (d)(iii) and sections 1 and 2 of the data booklet.
(If you did not obtain an answer to (d)(iii) use a value of 2.0 kJ mol−1, although this is not the correct answer).
[2]
Markscheme
«ln Kc= – (3.4 × 103 J mol–1 /8.31 J K–1 mol–1 × 298 K)» = –1.37 ✔
«Kc =» 0.25 ✔
Award [2] for “0.45” for the use of 2.0 kJ mol–1 for ΔG⦵.

Syllabus sections
Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.4—As a reaction approaches equilibrium, ΔG becomes less negative and finally reaches zero. Perform calculations using the equation ΔG = ΔG⦵ + RT lnQ and its application to a system at equilibrium ΔG⦵ = −RT lnK.