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Fractional distillation of kerosene
Central heating boilers can also burn kerosene. Kerosene is produced from crude oil in a fractionating column using fractional distillation. In the first step, crude oil is heated and hydrocarbon vapours are formed.
Explain how kerosene is produced from these hydrocarbon vapours.
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Marking points
- 1 Describes the temperature gradient/the column becoming cooler higher up.
- 2 States that kerosene vapour condenses.
- 3 Links kerosene condensation to the level matching its boiling-point range.
Full-mark answer
The fractionating column has a temperature gradient and becomes cooler higher up. Kerosene vapour rises until it reaches the level at which the temperature is within kerosene’s boiling-point range, where it condenses and is collected.
Why this answer loses marks
Kerosene evaporates at the top because the column is hottest there.
The column becomes cooler higher up, and kerosene is collected when its vapours condense at the matching boiling range.