Before using a new fractionating column to process crude oil, engineers test it with a mixture of five alkanes.
The table shows information about the alkanes.
| Alkane | Number of carbon atoms in each molecule | Boiling point (∘C^{\circ}\text{C}∘C) |
|---|---|---|
| P | 6 | 69 |
| Q | 10 | 174 |
| R | 14 | 254 |
| S | 18 | 316 |
| T | 24 | 391 |
The furnace and the trays in the column are at the temperatures shown.
| Position | Temperature (∘C^{\circ}\text{C}∘C) |
|---|---|
| furnace | 350 |
| lower tray | 290 |
| middle tray | 210 |
| upper tray | 110 |
| top tray | 30 |
Alkane R has 14 carbon atoms in each molecule.
Give the molecular formula of alkane R.
Predict the first tray on which alkane Q condenses as its vapour rises through the column.
Use the data to explain your answer.
Describe and explain what happens to the five alkanes as the test mixture passes through the fractionating column.
Use the data and ideas about molecular size and forces between molecules.
During the test, a fault causes the upper tray to reach 190 ∘C190\ ^{\circ}\text{C}190 ∘C while all the other temperatures stay the same. Include a prediction of how this affects the substances collected at the top tray.
131 exam-style questions on OCR GCSE Chemistry 6.2 Organic chemistry, covering 6.2.1 Crude oil and fractional distillation, 6.2.2 Cracking and dependence on hydrocarbons, 6.2.3 Functional groups and homologous series, 6.2.4 Reactions of alkanes, alkenes and alcohols, 6.2.5 Addition polymerisation and repeat units, 6.2.6 Naturally occurring polymers, 6.2.7 Chemical cells and fuel cells, and 6.2.8 Condensation polymerisation and how to make one. Each one has a worked solution and a mark scheme showing where the marks go.