User interface language: English | Español

Date November 2019 Marks available 2 Reference code 19N.3.sl.TZ0.14
Level SL Paper 3 Time zone TZ0
Command term Explain Question number 14 Adapted from N/A

Question

Ethanol is a biofuel that can be mixed with gasoline.

Write the equation for the complete combustion of ethanol.

[1]
a.

Outline the evidence that relates global warming to increasing concentrations of greenhouse gases in the atmosphere.

[2]
b.

Explain, including a suitable equation, why biofuels are considered to be carbon neutral.

[2]
c.

State the type of reaction that occurs when ethanol reacts with vegetable oil to form biodiesel.

[1]
d.

Markscheme

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (l) ✔

a.

Any two of:
«showing strong» correlation between «atmospheric» CO2 concentration/greenhouse gas concentration and average «global/surface/ocean» temperature ✔

lab evidence that greenhouse gases/CO2 absorb(s) infrared radiation ✔

«advanced» computer modelling ✔

ice core data ✔

tree ring data ✔

ocean sediments / coral reefs / sedimentary rocks data ✔

NOTE: Do not accept “global warming” for “average temperature”.
Do not accept “traps/reflects heat” OR “thermal energy”.
Evidence must be outlined and connected to data.
Accept references to other valid greenhouse gases other than carbon dioxide/CO2, such as methane/CH4 or nitrous oxide/N2O.

b.

biofuel raw material/sugar/glucose formed by photosynthesis
OR
biofuel raw material/sugar/glucose uses up carbon dioxide during its formation
OR
biofuel from capturing gases due to decaying organic matter formed from photosynthesis ✔

6CO2 (g) + 6H2O (l) → C6H12O6 (aq) + 6O2 (g) ✔

NOTE: Accept arguments based on material coming from plant sources consuming carbon dioxide/carbon for M1.

c.

transesterification
OR
«nucleophilic» substitution/SN

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Options » C: Energy » C.4 Solar energy
Show 31 related questions
Options » C: Energy
Options

View options