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A-LevelChemistryHydrocarbons9701/21 · May/June 2023 · Q515 Marks

Molecule M is present in petrol, a fuel used in cars. M is a saturated, non-cyclic hydrocarbon. M contains eight carbon atoms.

  1. (a)(i)Construct an equation for the complete combustion of M.[2]
  2. (a)(ii)Describe how the composition of products differs when incomplete combustion of M occurs.[2]
  3. (b)(i)When petrol is burned in an internal combustion engine, oxides of nitrogen are released into the atmosphere. Oxides of nitrogen are responsible for the formation of acid rain. Suggest the conditions required for the production of oxides of nitrogen during combustion of M in an internal combustion engine. Use an appropriate equation in your answer.[2]
  4. (b)(ii)Describe how acid rain is formed in the atmosphere in the presence of oxides of nitrogen and SO₂. Identify the role of the oxides of nitrogen in this process. Include all relevant equations.[3]
  5. (b)(iii)State one other type of air pollution that is caused by the production of oxides of nitrogen in an internal combustion engine.[1]
  6. (c)(i)Biodiesel T is a fuel made from vegetable oil R. Fig. 5.1 shows the production of T from R in a two-step process. [Figure 5.1] In step 1 all three ester groups in R react. Suggest a suitable reagent and conditions for step 1.[1]
  7. (c)(ii)Draw the structural formula of J in the box in Fig. 5.1.[1]
  8. (c)(iii)Name the type of reaction that occurs in step 2.[1]
  9. (c)(iv)Name organic reagent G used in step 2.[1]
  10. (c)(v)L is called decanoic acid. Use systematic nomenclature to deduce the name of T.[1]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

  1. [2] M1 correct formula of M C₈H₁₈; M2 balanced equation showing complete combustion of M: C₈H₁₈ + 12½ O₂ → 8CO₂ + 9H₂O
  2. [2] • C; • CO; • unburnt hydrocarbons; • less/no CO₂; Two correct for one mark, three correct for two marks.
  3. [2] M1 • high temperature • high pressure • N₂; Any two correct for M1; M2 N₂ + O₂ → 2NO OR N₂ + 2O₂ → 2NO₂ OR N₂ + xO₂ → 2NOₓ
  4. [3] M1 NO₂ is the catalyst (for SO₂ → SO₃) OR catalytic oxidation (of SO₂) by NO₂; M2 NO₂ + SO₂ → NO + SO₃ AND 2NO + O₂ → 2NO₂; M3 SO₃ reacts with rain OR moisture/water (in atmosphere) to form sulfuric acid / H₂SO₄ OR SO₃ + H₂O → H₂SO₄
  5. [1] photochemical smog / PAN
  6. [1] heat AND any dilute named mineral acid e.g. dilute sulfuric acid / dilute hydrochloric acid
  7. [1] [Structure of J: HO-CH₂-CH(OH)-CH₂-OH]
  8. [1] condensation
  9. [1] methanol
  10. [1] methyl decanoate

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About this question

Topic
Hydrocarbons, A-Level Chemistry (syllabus 9701). Structured question, 15 marks.
Source
A-Level Chemistry, May/June 2023 Paper 2 Variant 1, question 5.

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