Edexcel IGCSEChemistryGeneral Applications13 Marks
19. This question is about crude oil and fuels.
- (a)(i)What is the meaning of the term hydrocarbon?[1]
- (a)(ii)Describe how crude oil is separated into fractions.[4]
- (a)(iii)A student describes a fraction from crude oil as a 'liquid with a single boiling point'. Comment on the accuracy of this statement.[1]
- (b)(i)Suggest an impurity that may be present in a fossil fuel.[1]
- (b)(ii)Explain how this impurity causes environmental problems.[2]
- (c)(i)Describe a chemical test to show that ethene is an unsaturated hydrocarbon.[2]
- (c)(ii)Ethene can be converted into poly(ethene). Complete the equation to show the formation of poly(ethene). [Figure 8 - Equation with ethene monomer and then empty bracketed repeating unit with 'n'][2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- 19 (a) (i)
- compound containing hydrogen and carbon only (1)
- 19 (a) (ii)
- • (crude oil is) heated (1)
- • vapourises / turns into gas (1)
- • enters fractionating column (1)
- • (vapours) condense at different temperatures / fractions have different boiling points (1)
- (Max 4)
- 19 (a) (iii)
- • inaccurate / incorrect (1)
- • fractions are mixtures / contain a range of boiling points (1)
- (Max 1 for incorrect, or 2 for both points)
- 19 (b) (i)
- sulfur / nitrogen (1)
- (Allow named compounds of sulfur or nitrogen e.g. sulfur dioxide)
- 19 (b) (ii)
- (sulfur)
- • sulfur dioxide causes acid rain (1)
- • acid rain damages buildings / statues / plants / trees / affects aquatic life (1)
- (OR)
- (nitrogen)
- • nitrogen oxides cause acid rain (1)
- • acid rain damages buildings / statues / plants / trees / affects aquatic life (1)
- (OR)
- • nitrogen oxides cause photochemical smog / respiratory problems (1)
- (Max 2)
- 19 (c) (i)
- • add bromine water (1)
- • (bromine water changes from) orange / brown to colourless (1)
- (Allow bromine water decolourises)
- 19 (c) (ii)
- [ Figure 8 - Structure of repeating unit ]
- (n) (CH₂-CH₂) (1)
- single bond between carbons (1)
- bracket (around repeating unit) and n (outside) (1)
- (Ignore charges)
- (Allow ECF for bracket and n if structure is incorrect)
- (Max 2)
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