1. 1
   A student is investigating an unlabelled sample of an organic compound and determines its molecular formula to be C5H10. The student is told that the compound could belong to either the alkane or the alkene homologous series.

   (a)

   Using the general formulae for alkanes (CnH2n+2) and alkenes (CnH2n), which homologous series does a compound with molecular formula C5H10 belong to?

   [1 mark]

   • AAlkane, since C5H12 fits CnH2n+2
   • BAlkene, since C5H10 fits CnH2n
   • CBoth the alkane and alkene series equally
   • DNeither series, since C5H10 does not fit either general formula

   (b)

   What term describes two or more compounds that have the same molecular formula but different structural formulae?

   [1 mark]

   • AIsotopes
   • BHomologues
   • CIsomers
   • DAllotropes

   (c)

   State what is meant by the term homologous series, and explain how being part of the same homologous series affects the chemical properties of the compounds within it.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician burns a sample of an unspecified hydrocarbon fuel under two different conditions: first with a plentiful supply of oxygen, and then with a limited supply of oxygen, and analyses the gaseous products formed in each case.

   (a)

   When the hydrocarbon is burned with a plentiful supply of oxygen, which two products are formed by complete combustion?

   [1 mark]

   • ACarbon monoxide and water
   • BCarbon and water
   • CCarbon dioxide and water
   • DCarbon dioxide and hydrogen

   (b)

   When the same hydrocarbon is burned with a limited supply of oxygen, carbon monoxide is formed instead of carbon dioxide. Why is carbon monoxide gas dangerous to breathe in, even in small amounts?

   [1 mark]

   • AIt reacts with oxygen in the lungs to produce carbon dioxide
   • BIt is a strong acid that burns the lining of the lungs
   • CIt displaces nitrogen from the air, causing suffocation
   • DIt binds to haemoglobin in red blood cells, reducing the blood's ability to carry oxygen around the body

   (c)

   Explain, in terms of the availability of oxygen, why incomplete combustion produces carbon monoxide (or carbon/soot) instead of carbon dioxide.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A chemist exposes a mixture of ethane gas and bromine vapour to ultraviolet light in a sealed glass tube, and after a period of time observes that the initially orange colour of the bromine vapour has faded, while a colourless gas and a colourless liquid are found inside the tube.

   (a)

   Name the type of reaction that has taken place between ethane and bromine, and write a balanced symbol equation for the reaction that forms bromoethane and hydrogen bromide.

   [3 marks]

   (b)

   State the condition needed for this reaction to occur, and explain, in terms of saturation, why ethane can only react with bromine by substitution and not by addition.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A polymer scientist has a sample of pent-1-ene, CH2=CHCH2CH2CH3, and first investigates its reaction with bromine water, before using large quantities of the same monomer to manufacture an addition polymer called poly(pent-1-ene).

   (a)

   Describe what would be observed when pent-1-ene is shaken with orange bromine water, explain this observation in terms of the reaction taking place, and explain how this test could be used to distinguish pent-1-ene from an alkane of a similar size, such as pentane.

   [6 marks]

   (b)

   Explain, in terms of the reaction taking place, how the pent-1-ene monomer molecules join together to form the addition polymer poly(pent-1-ene), and deduce the repeat unit of poly(pent-1-ene) by describing, in words, the structure that forms when the C=C double bond opens up during polymerisation.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A student heats ethanol gently with potassium dichromate(VI) solution acidified with dilute sulfuric acid in a test tube, and observes the orange dichromate solution slowly turn green as the ethanol is oxidised to a carboxylic acid.

   (a)

   Which carboxylic acid is formed when ethanol is oxidised in this way?

   [1 mark]

   • AMethanoic acid
   • BEthanoic acid
   • CPropanoic acid
   • DButanoic acid

   (b)

   The colour change from orange to green shown by acidified potassium dichromate(VI) indicates that a chemical change has taken place. What type of reaction is occurring in the dichromate solution itself?

   [1 mark]

   • AThe dichromate ions are being reduced
   • BThe dichromate ions are being neutralised
   • CThe dichromate ions are decomposing thermally
   • DThe dichromate ions are precipitating out of solution

   (c)

   Describe, in words, one other method by which ethanol can be oxidised to form ethanoic acid, other than heating with acidified potassium dichromate(VI).

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A student adds excess solid sodium carbonate to a test tube of dilute propanoic acid, and observes vigorous effervescence as a colourless gas is produced, which turns limewater cloudy when passed through it.

   (a)

   What is the name of the salt formed in this reaction between propanoic acid and sodium carbonate?

   [1 mark]

   • ASodium propanoate
   • BSodium propanate
   • CPropanoic sodium
   • DSodium carbonate propanoate

   (b)

   The gas produced turns limewater cloudy. What is the identity of this gas, and what type of ion in the propanoic acid is responsible for this reaction occurring?

   [1 mark]

   • AOxygen gas; produced by hydroxide ions in the acid
   • BHydrogen gas; produced by carboxylic acid molecules acting as a base
   • CSulfur dioxide gas; produced from sulfur impurities in the acid
   • DCarbon dioxide gas; produced because propanoic acid is a source of hydrogen ions that react with the carbonate

   (c)

   Write a balanced symbol equation, including state symbols, for the reaction between propanoic acid (CH3CH2COOH) and sodium carbonate (Na2CO3), given that the other products are sodium propanoate, water and carbon dioxide.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A food scientist prepares a small sample of an ester by heating propan-1-ol (CH3CH2CH2OH) with ethanoic acid (CH3COOH) in the presence of a few drops of concentrated sulfuric acid as a catalyst, producing a fruity-smelling liquid and water.

   (a)

   Name the ester formed in this reaction, and write the balanced symbol equation for its formation from propan-1-ol and ethanoic acid.

   [3 marks]

   (b)

   State the role of the concentrated sulfuric acid in this reaction, describe one physical property of esters that allows the food scientist to identify that an ester has been made, and give one use of esters based on this property.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A materials scientist reacts a dicarboxylic acid monomer, HOOC–CH2–COOH, with a diol monomer, HO–CH2CH2–OH, in a condensation polymerisation reaction to form a polyester, releasing water as a by-product with every new bond formed.

   (a)

   Explain what is meant by condensation polymerisation, and describe, in words, how the dicarboxylic acid and diol monomers join together repeatedly to form a long polyester chain.

   [6 marks]

   (b)

   The new bond formed between the acid and diol monomers in this reaction is the same type of functional group found in esters made from a simple monocarboxylic acid and a monohydric alcohol, such as ethyl ethanoate. Explain, by comparing the reaction of ethanol with ethanoic acid to the reaction described above, why the link formed in the polyester is described as an ester linkage.

   [6 marks]

   Total for question 8: 12 marks

End of questions