| Date | May 2018 | Marks available | 1 | Reference code | 18M.3.sl.TZ2.14 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Deduce | Question number | 14 | Adapted from | N/A |
Question
One method of producing biodiesel is by a transesterification process.
Deduce the equation for the transesterification reaction of pentyl octanoate, C7H15COOC5H11, with methanol.
Outline why the ester product of this reaction is a better diesel fuel than pentyl octanoate.
Markscheme
C7H15COOC5H11(l) + CH3OH(l) → C7H15COOCH3(l) + C5H11OH(l)
OR
C13H26O2(l) + CH4O(l) → C9H18O2(l) + C5H12O(l)
OR
Accept correct equation in any format eg, skeletal, condensed structural formula, etc.
Accept equations with equilibrium arrow.
[1 mark]
less viscous «and so does not need to be heated to flow»
OR
less likely to undergo incomplete combustion
OR
fewer intermolecular/London/dispersion forces
OR
vaporizes easier
Ignore equation and products in 14a.
Accept “van der Waals’/vdW” for “London”.
[1 mark]
Examiners report
Syllabus sections
-
18M.3.sl.TZ1.11a.ii:
State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.
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18M.3.hl.TZ1.13b:
State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.
- 16N.3.sl.TZ0.14a: State the equation for the complete transesterification of the triglyceride given below with...
- 18N.3.sl.TZ0.11c.ii: Describe how vegetable oils can be converted to a more suitable fuel.
- 18N.3.sl.TZ0.11c.i: State a physical property of vegetable oils that makes them very difficult to use as fuel in...
- 18N.3.sl.TZ0.11b: Light can be absorbed by chlorophyll and other pigments. Consider molecules A and B...
- 18N.3.hl.TZ0.14b.i: State a physical property of vegetable oils that makes them very difficult to use as fuel in...
- 18N.3.hl.TZ0.14b.ii: Describe how vegetable oils can be converted to a more suitable fuel.
-
17M.3.sl.TZ1.15d:
Determine the specific energy, in kJg−1, and energy density, in kJcm−3, of a particular biodiesel using the following data and section 1 of the data booklet.
Density = 0.850 gcm−3; Molar mass = 299 gmol−1;
Enthalpy of combustion = 12.0 MJmol−1.
- 17N.3.sl.TZ0.15b: Vegetable oils are too viscous for use as liquid fuels. Describe, using an equation, how a...
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18M.3.hl.TZ1.13a:
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.
-
17M.3.sl.TZ1.15b:
Deduce the formula of the biodiesel formed when the vegetable oil shown is reacted with the reagents in (a).
- 17N.3.sl.TZ0.15a: State the structural feature of chlorophyll that enables it to absorb visible light.
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17M.3.sl.TZ2.12b:
Coloured molecules absorb sunlight. Identify the bonding characteristics of such molecules.
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19M.3.hl.TZ1.17c:
Biodiesel containing ethanol can be made from renewable resources.
Suggest one environmental disadvantage of producing biodiesel from renewable resources.
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19N.3.sl.TZ0.14a:
Write the equation for the complete combustion of ethanol.
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16N.3.sl.TZ0.14b:
Outline why the fuel produced by the reaction in (a) is more suitable for use in diesel engines than vegetable oils.
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18M.3.sl.TZ2.14b:
Outline why the ester product of this reaction is a better diesel fuel than pentyl octanoate.
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19M.3.sl.TZ1.13c:
Biodiesel containing ethanol can be made from renewable resources.
Suggest one environmental disadvantage of producing biodiesel from renewable resources.
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17M.3.sl.TZ1.15c:
Explain, in terms of the molecular structure, the critical difference in properties that makes biodiesel a more suitable liquid fuel than vegetable oil.
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19N.3.sl.TZ0.14c:
Explain, including a suitable equation, why biofuels are considered to be carbon neutral.
- 19N.3.sl.TZ0.14d: State the type of reaction that occurs when ethanol reacts with vegetable oil to form biodiesel.
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19M.3.sl.TZ2.12a:
The structure of chlorophyll is given in section 35 of the data booklet.
State the feature of the chlorophyll molecule that enables it to absorb light in the visible spectrum.
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17M.3.sl.TZ1.15a:
State two reagents required to convert vegetable oil to biodiesel.
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20N.3.sl.TZ0.9d:
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.
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19M.3.sl.TZ2.12b:
Evaluate the use of biodiesel in place of diesel from crude oil.
Strength:
Limitation:
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18M.3.sl.TZ1.11b:
Outline why biofuels are considered more environmentally friendly, even though they produce more carbon dioxide per kJ of energy than petroleum based fuels.
- 20N.3.hl.TZ0.11d: A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a...
-
18M.3.sl.TZ1.11a.i:
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.
-
19M.3.hl.TZ2.17:
This question is about biofuel.
Evaluate the use of biodiesel in place of diesel from crude oil.
- 20N.3.sl.TZ0.9e: Contrast the molecular structures of biodiesel and the vegetable oil from which it is formed.
