Question 18M.3.sl.TZ1.10
| Date | May 2018 | Marks available | [Maximum mark: 7] | Reference code | 18M.3.sl.TZ1.10 |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Determine, Explain, Identify, Outline | Question number | 10 | Adapted from | N/A |
The increased concentration of carbon dioxide in the atmosphere is thought to result from the increased combustion of fossil fuels such as petroleum.
Identify an element, other than carbon and hydrogen, found at significant concentrations in fossil fuels.
[1]
nitrogen/N
OR
oxygen/O
OR
sulfur/S
Accept “phosphorus/P”.
[1 mark]
Petroleum contains many hydrocarbons. Explain how these are separated by fractional distillation.
[3]
Any three of:
different molar masses
OR
different strengths of intermolecular forces
different boiling points
temperature in «fractionating» column decreases upwards
«components» condense at different temperatures/heights
OR
«component with» lower boiling point leaves column first
[3 marks]
Determine the specific energy and energy density of petrol (gasoline), using data from sections 1 and 13 of the data booklet. Assume petrol is pure octane, C8H18. Octane: molar mass = 114.26 g mol−1, density = 0.703 g cm−3.
[2]
specific energy «= = » = 47.9 «kJ g–1»
energy density « = specific energy × density = 47.9 kJ g–1 × 0.703 g cm–3» = 33.7 «kJ cm–3 »
Do not accept “–47.9 «kJ g–1»”.
Do not accept “–33.7 «kJ cm–3»” unless “–47.9 «kJ g–1»” already penalized.
[2 marks]
Outline why the energy available from an engine will be less than these theoretical values.
[1]
energy is lost «to the surroundings» as heat/sound/friction
OR
energy is lost to the surroundings «as heat/sound/friction»
OR
incomplete combustion
Do not accept just “energy is lost”.
[1 mark]