AlcoholsEdexcel A-Level Chemistry: Subtopic test

1. 1
   A technician is given four structural isomers of molecular formula C₄H₁₀O: butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methylpropan-2-ol. She will warm each with acidified potassium dichromate(VI) solution and compare the results.

   (a)

   Which of the four isomers is a tertiary alcohol?

   [1 mark]

   • AButan-1-ol
   • BButan-2-ol
   • C2-Methylpropan-1-ol
   • D2-Methylpropan-2-ol

   (b)

   Which isomer is oxidised by acidified potassium dichromate(VI) to a ketone?

   [1 mark]

   • AButan-1-ol
   • BButan-2-ol
   • C2-Methylpropan-1-ol
   • D2-Methylpropan-2-ol

   (c)

   Explain why 2-methylpropan-2-ol does not change the colour of acidified potassium dichromate(VI) solution when warmed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemist converts propan-1-ol into three different halogenoalkanes: 1-chloropropane, 1-bromopropane and 1-iodopropane. A different reagent or reagent mixture is needed for each halogen.

   (a)

   Which reagent converts propan-1-ol into 1-chloropropane?

   [1 mark]

   • APotassium bromide and 50% concentrated sulfuric acid
   • BRed phosphorus and iodine
   • CPhosphorus(V) chloride, PCl₅
   • DConcentrated phosphoric acid

   (b)

   Which products form when propan-1-ol reacts with PCl₅?

   [1 mark]

   • A1-Chloropropane, POCl₃ and HCl
   • B1-Chloropropane and H₃PO₄ only
   • CPropene, POCl₃ and HCl
   • DPropanal, PCl₃ and HCl

   (c)

   Write two equations to show how potassium bromide and 50% concentrated sulfuric acid convert propan-1-ol into 1-bromopropane. The first equation shows the formation of the reactive halogenating species.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student carries out Core Practical 5 on the oxidation of ethanol using acidified potassium dichromate(VI). In one experiment she wants to collect ethanal; in a second experiment she wants to make ethanoic acid.

   (a)

   Describe how she should carry out the experiment to collect ethanal, and explain why this method prevents further oxidation.

   [3 marks]

   (b)

   Describe how she should make ethanoic acid instead. Explain the method, state the colour change seen and write an equation using [O] for the oxidation of ethanol to ethanoic acid.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school technician needs to identify bottles of alcohols and to make and purify a halogenoalkane. Benedict's or Fehling's solution is available for the aldehyde test.

   (a)

   The technician has three unlabelled bottles: propan-1-ol, propan-2-ol and 2-methylpropan-2-ol. Describe how acidified potassium dichromate(VI) and Benedict's (or Fehling's) solution can be used to identify each alcohol, giving the observations.

   [6 marks]

   (b)

   The technician prepares 2-chloro-2-methylpropane by shaking 2-methylpropan-2-ol with concentrated hydrochloric acid in a separating funnel (Core Practical 6). Describe how a pure, dry sample of the product is obtained from the reaction mixture, explaining the purpose of each step.

   [6 marks]

   Total for question 4: 12 marks

End of questions