PAPER 2 EXAM Qs

• When an excess of water is added to ethanal a similar nucleophilic addition reaction occurs. CH3CHO(aq) + H2O(l) ⇌ CH3CH(OH)2(aq)

  Suggest why this reaction is slower than the reaction in Question 09.5. (with chloroethanal)

  • M1 C in C=O is less δ+ / less electron deficient
  • M2 Because CH3 attached is electron donating Or CH3 has a (positive) inductive effect
  • M3 So higher activation energy
• Explain, in terms of structure and bonding, why is BENZENE RING more thermodynamically stable than Kekule's model

  • Pi electrons are delocalised
• Suggest why chemists usually aim to design production methods

  • with fewer steps

  • with a high percentage atom economy.

  1. Less energy used OR Better yield

  • reduces practical losses, simpler plant,
  • 2) Less waste OR Less pollution
  • OR maximises the use of raw materials in the process into useful products, saves resources
• 0 9 . 1 State why the ozone layer is beneficial for living organisms.

  • Absorbs / prevents harmful UV
• Suggest an extra step to ensure that the mass of olive oil in the solution is recorded accurately. (In titration) [2 marks, 2022]

  • Extra step: Weigh the bottle after oil transfer (and record the mass)
  • Justification: Not all of the oil is transferred Or so that the mass of oil left in the bottle is accounted for Or find the exact mass of oil used
• 0 9 . 4 State the reason for inverting the flask several times.

  • 09.4 To ensure the solution is homogeneous
  • Allow evenly mixed/ distributed / uniform solution
• Disadvantages of Route A (2 step synthesis, KCN)

  • Lower yield (because of two steps)

  Disadvantages of Route B (Nucleophilic subs with amine)

  • FURTHER SUBSTITUTION IS LIKELY
• Suggest how you could show the atenolol produced by reduction of a ketone was a racemate and NOT a single enantiomer

  • shine plane polarized light
  • If racemate, no effect on plane polarized light as enantiomers rotate light opposite directions equally
• State the property of Sulfur dioxide (gas) that causes pollution when it enters rivers

  • acid(ic) / acidity / produces H +
  • OR lowers pH
• Draw a diagram to show the shape of a molecule of H2O Include any lone pairs of electrons.

  State the H−O−H bond angle.

  Explain this shape and bond angle.

  • 104.5 degrees
  • lone pairs repel more strongly than bonding pairs
  • so bond angle reduced from/less than 109½° / tetrahedral
  • ALLOW reduced by 2.5° per lone pair or 5°
• Suggest one reason why chlorobenzene (C6H5Cl) does not react with ammonia under normal conditions.

  • electron rich ring or benzene or pi cloud REPELS! nucleophile/ammonia
• Organic Synthesis Exam Question

  Give one disadvantage of Route A - sub with KCN, then reduction Ni + H2

  • Route A - lower YIELD because two steps
  • OR KCN is poisonous (3.8 spec) // Expensive LiAlH4

  Route B - Nucleophilic substitution with excess ammonia

  - Further reaction/substitution likely // impure product
• Give one advantage and one disadvantage of manufacturing ethanol by fermentation rather than by hydration. Do not include energy consumption or cost.

  ADVANTAGES

  • low technology
  • renewable feedstock / resource
  • allowed for use in drinks, perfumes
  • considered to be green
• Give one advantage and one disadvantage of manufacturing ethanol by fermentation rather than by hydration. Do not include energy consumption or cost.

  DISADVANTAGES

  • slow
  • low yield
  • significant land use (for growing sugar canes)
  • has to be distilled
  • (labour intensive?)
• State one advantage and one disadvantage of the production of ethanol by the hydration of ethene compared to the fermentation of glucose.

  ADVANTAGE

  • Fast reaction OR pure product
  • OR continuous process
  • OR cheap on manpower
  • OR high yield, 100% alcohol
• State one advantage and one disadvantage of the production of ethanol by the hydration of ethene compared to the fermentation of glucose.

  Disadvantage

  • High technology
  • OR ethene from non renewable source
  • OR expensive equipment not just costly
• In the manufacture of margarine, unsaturated vegetable oils such as sunflower oil are hardened.

  (i) State the reagent and conditions used in this process

  • Reagent = Hydrogen
  • Conditions - Nickel catalyst
  • Heat (100-200 degrees)
• Nonane is often found in fuel for jet engines. Combustion in jet engines produces pollutants including nitrogen monoxide (NO). Explain how this nitrogen monoxide is formed. [2 marks]

  • M1 nitrogen and oxygen from air react
  • M2 at high temperature (if temperature stated, over 1000C)
• Use your understanding of properties of PVC to explain whether you'd expect a plasticiser in PVC used to insulate electrical cables [2 marks] = Need both ideas that

  • it is present
  • AND because PVC needs to be flexible / bendy
• The characteristics of a homologous series, a series of compounds containing the same functional group

  • Any two from
  • chemically similar or chemically the same or react in the same way
  • same functional group
  • same general formula
  • differ from CH2
• Explain what is meant by the term fuel

  • release (heat) ENERGY! (when burned) (1)
  • OR provides a (useable form of) energy
  • OR is a source of energy
• Crude oil is separated into fractions by fractional distillation. Outline how different fractions are obtained by this process. [3 marks]

  • Crude oil is heated to vaporise it / oil VAPOURISED (1)
  • (Vapour passed into fractionating) tower / COLUMN (1)
  • Top of tower cooler than bottom or negative temperature gradient (1) OR condenses at different temperatures
  • fractions separated by boiling point
• Use the data given above to explain why catalytic cracking of crude oil fractions is commercially important.

  • Identify shortfall in supply - e.g. petrol / small molecules (1)
  • Higher value products OR more useful products (1)