| Date | May 2018 | Marks available | 1 | Reference code | 18M.3.sl.TZ1.11 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
One suggestion for the reduction of carbon footprints is the use of biofuels, such as vegetable oils, as a substitute for petroleum based fuels.
Outline the major technical problem affecting the direct use of vegetable oils as fuels in internal combustion engines and the chemical conversion that has overcome this.
State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.
Outline why biofuels are considered more environmentally friendly, even though they produce more carbon dioxide per kJ of energy than petroleum based fuels.
Markscheme
viscosity «of vegetable oils is too high»
transesterification
OR
«conversion into» alkyl/methyl/ethyl esters
[2 marks]
R–CO–O–CH3/RCOOMe
OR
R–CO–O–C2H5/RCOOEt
[1 mark]
«growing oil producing» plants absorbs carbon dioxide from the atmosphere
OR
«combustion of» petroleum based fuels releases carbon stored «for millions of years»
Accept “biofuels renewable” OR “petroleum based fuels non-renewable”.
Accept “waste vegetable oils can be converted to biofuels/biodiesel”.
Accept “biofuels do not contain sulfur”.
[1 mark]
