O-LevelChemistryOrganic Chemistry5070/22 · May/June 2021 · Q510 Marks

Petroleum (crude oil) provides the raw materials for making ethanol and ammonia.

(a)Describe how petroleum (crude oil) is separated to make fractions such as naphtha and petrol (gasoline).[2]
(b)(i)Explain how the molecular formula C₁₁H₂₄ shows the compound is an alkane.[1]
(b)(ii)Construct an equation to show the cracking of C₁₁H₂₄ to make ethene and an alkane only.[1]
(c)Describe how hydrogen is converted into ammonia in the Haber process. Include the conditions used in the Haber process.[3]
(d)State one other use for hydrogen.[1]
(e)(i)Name the compound.[1]
(e)(ii)State one condition for this reaction.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[2] Any two from: crude oil heated / crude oil vapourised (1) fractional distillation / use of fractionating column / use of fractionating tower (1) separated because of different boiling points (1) fractions move up the column at different rates / fractions condense at different heights in the column (1)
[1] fits the formula CnH₂n+₂ / it is C₁₁H(₁₁ × 2) + ₂
[1] C₁₁H₂₄ → C₂H₄ + C₉H₂₀/C₁₁H₂₄ → 2C₂H₄ + C₇H₁₆/ C₁₁H₂₄ → 3C₂H₄ + C₅H₁₂/C₁₁H₂₄ → 4C₂H₄ + C₃H₈/ C₁₁H₂₄ → 5C₂H₄ + CH₄
[1] (reaction with) nitrogen (1)
[0] AND
[1] Any two conditions from:
[0] Fe (catalyst) (1)
[0] 400 to 500 °C (1)
[0] 200 to 400 atmosphere (pressure) (1)
[1] making margarine / fuel cells / fuel
[1] water / steam
[1] heat / high temperature / catalyst

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