1. 1
   A technician in a petrochemical refinery laboratory is given four unlabelled sample bottles of pure organic compounds. Bottle W is later confirmed to have the molecular formula C4H10.

   (a)

   Which statement about bottle W is correct?

   [1 mark]

   • AIt is an alkane, since it fits the general formula CnH2n+2
   • BIt is an alkene, since it fits the general formula CnH2n
   • CIt is an alcohol, since it fits the general formula CnH2n+1OH
   • DIt is a carboxylic acid, since it fits the general formula CnH2n+1COOH

   (b)

   Bottle X in the same laboratory is confirmed to have the molecular formula C3H6. Which term correctly describes bottle X?

   [1 mark]

   • ASaturated
   • BUnsaturated
   • CAmphoteric
   • DHydrated

   (c)

   The technician notes that bottles W and X, together with two other bottles, belong to two different homologous series. State two characteristics shared by all members of a single homologous series.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A biofuel production plant tests a sample of pure ethanol before blending it into vehicle fuel. Quality control compares the ethanol sample against a sample of butane taken from the same storage facility.

   (a)

   Which functional group is present in ethanol?

   [1 mark]

   • A-COOH
   • B-CHO
   • CC=C
   • D-OH

   (b)

   The quality control chemist also tests a sample of butane, C4H10. Which statement correctly compares butane with ethanol, C2H6O?

   [1 mark]

   • AEthanol is saturated but butane is unsaturated
   • BButane is saturated but ethanol is unsaturated
   • CBoth butane and ethanol are saturated compounds
   • DBoth butane and ethanol are unsaturated compounds

   (c)

   The plant chemist finds that a fourth sample bottle, labelled Y, has the same molecular formula as butan-1-ol but different physical properties. Define the term structural isomers and explain how this observation relates to bottle Y.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A historian studying the notebooks of a 19th-century chemist finds a record describing 'the sour compound obtained from soured wine', which modern analysis identifies as ethanoic acid, CH3COOH. Elsewhere in the same notebook, the chemist also describes a gaseous compound obtained by heating rock and lime, later identified as an alkene with the molecular formula C4H8.

   (a)

   Identify the functional group present in ethanoic acid, state the homologous series to which it belongs, and show that ethanoic acid fits the general formula of this series.

   [3 marks]

   (b)

   The historian also finds a description of the gaseous alkene with molecular formula C4H8. Explain the difference between a molecular formula and a structural formula, and use this to explain why C4H8 alone could not have told the 19th-century chemist which specific alkene had been produced.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school chemistry club is investigating the alcohol homologous series, starting with methanol and ending with butanol. Two of the students discover that one member of the series, with the formula C4H9OH, can be drawn in more than one way.

   (a)

   Explain what is meant by a homologous series, and describe, with reference to the alcohols, the general characteristics that all members of a homologous series share.

   [6 marks]

   (b)

   The students discover that the alcohol with molecular formula C4H9OH can be drawn as more than one distinct structure, such as butan-1-ol and butan-2-ol. Explain what is meant by structural isomerism, and describe how the naming of these two isomers reflects the underlying difference in their structures.

   [6 marks]

   Total for question 4: 12 marks

End of questions