DP Chemistry (last assessment 2024)
Question 18M.3.sl.TZ1.b
| Date | May 2018 | Marks available | [Maximum mark: 3] | Reference code | 18M.3.sl.TZ1.b |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 3]
18M.3.sl.TZ1.b
The increased concentration of carbon dioxide in the atmosphere is thought to result from the increased combustion of fossil fuels such as petroleum.
Petroleum contains many hydrocarbons. Explain how these are separated by fractional distillation.
[3]
Markscheme
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]
