Question 20N.1A.SL.TZ0.7
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.1A.SL.TZ0.7 |
| Level | SL | Paper | 1A | Time zone | TZ0 |
| Command term | Question number | 7 | Adapted from | N/A |
What is not an assumption of the kinetic model of an ideal gas?
A. Attractive forces between molecules are negligible.
B. Collision duration is negligible compared with time between collisions.
C. Molecules suffer negligible momentum change during wall collisions.
D. Molecular volume is negligible compared with gas volume.
[1]
C
Even though both difficulty and discrimination index are acceptable a significant number of candidates chose incorrect options B or D. The examiners appreciated that this was a challenging question which required some thought partly because it asked what is not an assumption. Candidates need to be aware that although questions are normally phased in a positive sense there will occasionally be ones like this and they need to hold the idea of 'not' when looking at the possible answers. A useful strategy is to look for correct assumptions and when those are identified there should be just one left — the required answer.