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• This document has 20 pages. Any blank pages are indicated.
• Cambridge O Level
• DC (MS/JG) 201610/3
• © UCLES 2021
• CHEMISTRY 5070/22 Paper 2 Theory May/June 2021 1 hour 30 minutes
• Section A


  Answer all questions
• Section B


  Answer three questions
• You must answer on the question paper.
• No additional materials are needed.
• Write your name, centre number and candidate number in the boxes at the top of the page.
• Write your answer to each question in the space provided.
• Do not use an erasable pen or correction fluid.
• Do not write on any bar codes.
• You may use a calculator.
• You should show all your working and use appropriate units.
• The total mark for this paper is 75.
• The number of marks for each question or part question is shown in brackets [ ].
• The Periodic Table is printed in the question paper.
• Compound A


  C

  C

  H

  H3C

  H3C

  CH3

  CH3

  CH3

  CH3
• Compound B


  H2C

  H3C

  H3C

  H2C

  CH2

  CH2

  C

  O

  C

  H

  H

  H

  H

  H

  H
• Compound C


  O

  C

  C

  H

  O

  H

  F
• Compound D


  C

  O

  C

  H

  O

  O

  CH3
• Compound E


  C

  CH3

  C

  H

  H

  H
• Compound G


  O

  H2N

  C

  O

  C

  H

  CH3

  H

  H

  H

  H

  H

  H
• (b) Identify two compounds that have a pH of less than 7 in aqueous solution.

  C, D
• Oxygen, sulfur, selenium, tellurium and polonium are in Group VI.
• (b) State one large-scale use for oxygen.

  Medical use, combustion, steel production
• (c)(i) Explain why both isotopes have the same chemical properties.

  They have the same number of protons (atomic number)
• (c)(ii) Give one difference in the atomic structure of these two isotopes.

  They have a different number of neutrons
• (d) Calculate the empirical formula of this compound.

  SeO2Cl2
• (e)(i) The temperature of the sample is decreased. The pressure remains constant.


  The volume decreases as the particles have less kinetic energy and occupy less space
• (e)(ii) The pressure of the sample is decreased. The temperature remains constant.


  The volume increases as the particles have more space to move around
• (a)(i) Name the type of polymer shown.

  Polyvinyl chloride (PVC)
• (a)(iii) Suggest one problem associated with this method of disposal.

  Releases toxic gases like HCl
• (b)(i) Suggest what is meant by the term biodegradable.


  Can be broken down by microorganisms
• (b)(iii) A factory uses 500 tonnes of lactic acid to make poly(lactic acid). The percentage yield is 100% but the mass of poly(lactic acid) made is less than 500 tonnes.
• (b)(iii) Explain why the mass of poly(lactic acid) made is less than 500 tonnes.

  Some mass is lost as water is removed during polymerisation
• (b)(iv) Suggest what happens to the lactic acid in this reaction.

  It is oxidised
• (b)(v) Write the ionic equation for this neutralisation.

  H+ + OH- → H2O
• (a) Predict two physical properties, other than electrical conductivity, of zinc bromide.

  High melting point, high boiling point