DP Chemistry (first assessment 2025)
Question 20N.2.SL.TZ0.d
Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.2.SL.TZ0.d |
Level | SL | Paper | 2 | Time zone | TZ0 |
Command term | Suggest | Question number | d | Adapted from | N/A |
d.
[Maximum mark: 1]
20N.2.SL.TZ0.d
A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a mixture over the use of pure gasoline. Exclude any discussion of cost.
[1]
Markscheme
Any one:
uses up fossil fuels more slowly ✔
lower carbon footprint/CO2 emissions ✔
undergoes more complete combustion ✔
produces fewer particulates ✔
higher octane number/rating
OR
less knocking ✔
prevents fuel injection system build up
OR
helps keep engine clean ✔
Accept an example of a suitable advantage even if repeated from 9c.
Examiners report
Another question where many candidates obtained the mark. In quite a few cases students repeated the argument for (c) and this allowed them to get two points for the same answer.

Syllabus sections
Reactivity 1. What drives chemical reactions? » Reactivity 1.3—Energy from fuels » Reactivity 1.3.4—Biofuels are produced from the biological fixation of carbon over a short period of time through photosynthesis. Understand the difference between renewable and non-renewable energy sources. Consider the advantages and disadvantages of biofuels.