DP Chemistry (first assessment 2025)
Question 22N.1A.HL.TZ0.16
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.16 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Identify | Question number | 16 | Adapted from | N/A |
16.
[Maximum mark: 1]
22N.1A.HL.TZ0.16
Which alkane has the lowest standard entropy, S⦵?
A. CH4 (g)
B. C2H6 (g)
C. C3H8 (g)
D. C4H10 (g)
[1]
Markscheme
A
Examiners report
Only just over half of the candidates were aware that entropy increases with molecular complexity, with the most favoured distractor (D) indicating that many consider the reverse to be the case. This question had a negative discrimination index, showing that top students actually performed worse than their peers.
Syllabus sections
Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.1—Entropy, S, is a measure of the dispersal or distribution of matter and/or energy in a system. The more ways the energy can be distributed, the higher the entropy. Under the same conditions, the entropy of a gas is greater than that of a liquid, which in turn is greater than that of a solid. Predict whether a physical or chemical change will result in an increase or decrease in entropy of a system. Calculate standard entropy changes, ΔS⦵, from standard entropy values, S⦵.