DP Chemistry (first assessment 2025)
Question 22M.2.HL.TZ2.4d(ii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.HL.TZ2.4d(ii) |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Justify, Predict | Question number | d(ii) | Adapted from | N/A |
d(ii).
[Maximum mark: 1]
22M.2.HL.TZ2.4d(ii)
(d(ii))
Predict, giving a reason, how the value of the ΔS⦵reaction would be affected if (g) were used as a reactant.
[1]
Markscheme
Δ lower/less positive AND same number of moles of gas
OR
Δ lower/less positive AND a solid has less entropy than a gas ✔
Examiners report
Some candidates confused the entropy change in this situation with absolute entropy of a solid and gas, or having realised that entropy would decrease lacked clarity in their explanations and lost the mark.
4(d)(ii)-(d)(iv): marks were lost due to inconsistency of units throughout, i.e., not because answers were given in different units to those required, but because candidates failed to convert all data to the same unit for calculations.
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.