AQA AS Chemistry C15 Alcohols Kerboodle Answers

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C15.1 Introduction AQA AS Chemistry C15 Alcohols Kerboodle Answers: Page No. 232

1 .Ans- 2.Ans-Primary: methanol Secondary: butan-2-ol Tertiary: 2-methylpentan-2-ol 3.Ans-Because the oxygen atom has two lone pairs which repel more than bonding pairs.

15.2 Ethanol production AQA AS Chemistry C15 Alcohols Kerboodle Answers: Page No. 234

1.Ans- By distillation. The ethanol has a lower boiling temperature than water and would distil off first. 2.ANS Advantages: IL is renewable. The process takes place at a low temperature. Disadvantages: The process is slow. lt is a batch process rather 1han a continuous one. An aqueous solution of ethanol is produced rather than pure ethanol. 3.Ans- Fermentation takes place at a relatively low temperature and distillation at a mud1 higher one. So the two cannot occur at the same time.

15.3 The reactions of alcohols AQA AS Chemistry C15 Alcohols Kerboodle Answers : Page No. 239

1.Ans- A carboxylic add is formed. b. A ketone is formed.

2. Ans-

This would require a C-C bond to break. 3.Ans-In distillation, the vapour is removed from the original flask and condensed in a different one. In refluxing, the vapour is condensed and returned to the original flask. 4.Ans- Gently oxidise the alcohols. In the case of the primary alcohol, an aldehyde will be formed that will give a positive silver mirror or Fehling’s test. In 1he case or the secondary alcohol, a ketone will be formed that will not give a positive silver mirror or Fehling’s test. 5.Ans- 6.Ans-

Practice questions: Page No. 240-241

1.Ans- Aqueous or solution in water or (aq) in the equation Yeast or zymase Anaerobic / absence of oxygen / absence of Air or neutral pH T in the range 30–40 °C only Fermentation b) Dehydration is the elimination of water or removal of combined water from a compound / molecule Catalyst = concentrated H2SO4 Or concentrated phosphoric acid Or aluminium oxide 2 .Ans-

1. a) (i)

Compounds with the same molecular formula but different structural formulae / different structures (ii) C₃H₆O (iii) CH₂

1. b)

Potassium dichromate (VI) / K₂Cr₂O₇ and acid / acidified / H₂SO₄ / H+ remains orange or no change or no reaction orange to green

1. c) choice of reagents

with the aldehyde C with the ketone D d) Bromine Alkane remains yellow / orange Or no change or no reaction The alkene goes colourless or decolourised 3 a) (i) (ii)  Pentanoic acid (b) Pentanal can be formed by the oxidation of an alcohol. (i) Pentan-1-ol (ii)  Primary 4.Ans- A

1. b) Balanced equation for the reaction of butan-1-ol with [O] to produce butanoic acid and water

or balanced equation for the reaction of butanal with [O] to produce butanoic acid Balanced equation for the reaction of butan-2-ol with [O] to produce butanone and water (c) Correct structure drawn for 2-methylpropan-2-ol name: 2-methylpropan-2-ol 5.Ans- (a) Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton / chain. (b) Compound A is butan-1-ol only Compound C is a ketone (c) (i) Oxidation or redox (ii) K₂Cr₂O₇ or potassium dichromate(VI) acidified or H₂SO₄ (iii) Heat under reflux (iv). 2-methylpropan-2-ol (v) (d) (i) Tollens’ reagent or ammoniacal silver nitrate or Fehling’s/Benedict’s reagent or acidified potassium dichromate(VI) (ii) Methylpropanal 6.Ans- a) Fermentation dehydration or elimination (b) (i) Yeast / zymase (ii) Concentrated sulfuric acid or phosphoric acid (c) (i) Primary (ii) Sugar or glucose or ethanol is renewable or ethanol does not contain sulfur-containing impurities or ethanol produces less pollution or isless smoky or less CO / C Banner 2

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