DP Chemistry (first assessment 2025)
Question 22M.1A.HL.TZ2.17
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.1A.HL.TZ2.17 |
| Level | HL | Paper | 1A | Time zone | TZ2 |
| Command term | Apply | Question number | 17 | Adapted from | N/A |
17.
[Maximum mark: 1]
22M.1A.HL.TZ2.17
Which term in the expression ΔG⦵ = ΔH⦵ − TΔS⦵ is an indirect measure of the entropy change of the surroundings when divided by T?
A. ΔG⦵
B. ΔH⦵
C. ΔS⦵
D. −TΔS⦵
[1]
Markscheme
B
Examiners report
This challenging question raised some debate and several teachers did not think it was suitable for this level. Most candidates chose -TΔS as “an indirect measure of the entropy change of the surroundings when divided by T”. While candidates are not expected to be familiar with the equation ΔS surroundings = -ΔHsystem/T, they could solve the question by recognizing that ΔH is the value that affects the surroundings while ΔS relates to the system. The wording of the question could have been simplified.
Syllabus sections
Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.2—Change in Gibbs energy, ΔG, relates the energy that can be obtained from a chemical reaction to the change in enthalpy, ΔH, change in entropy, ΔS, and absolute temperature, T. Apply the equation ΔG⦵ = ΔH⦵ − TΔS⦵ to calculate unknown values of these terms.