DP Chemistry (last assessment 2024)
Question 19M.3.sl.TZ1.13a
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.sl.TZ1.13a |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 1]
19M.3.sl.TZ1.13a
E10 is composed of 10 % ethanol and 90 % normal unleaded fuel.
(a)
Ethanol has a Research Octane Number (RON) of 108.6.
Outline how higher octane fuels affect engine performance.
[1]
Markscheme
increased AND fuels can be compressed more «before ignition» [✔]
Note: Accept “engines can be designed with higher compression ratio” OR “less chance of pre-ignition/autoignition/
knocking occurring”.
Examiners report
Over half the students could relate a high octane number to a reduced tendency for auto-ignition, though this was usually referred to as “knocking”.
