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Prelim Practice Paper: Preliminary Examination — question paper

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QQ/S4CH/PRELIM

Secondary 4 · Chemistry (G2 / G3)

Prelim Practice Paper

Preliminary Examination

Duration: 120 minutes
Total: 80 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Chemical equations should be balanced, with state symbols shown where the question asks for them.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is shown on its cover.

Original practice material written for the MOE Chemistry syllabus. It is not an official MOE or school examination paper. The full O-Level syllabus, with emphasis on the Sec 4 chapters.

For Examiner’s Use
Section A/ 20
Section B/ 60
Total/ 80

Section A: Multiple-choice questions[20 marks]

Answer all questions. For each question, write the letter (A, B, C or D) of the correct answer.

  1. 1

    The oxidation state of sulfur in the sulfate ion, SO₄²⁻, is

    1. A+2
    2. B+6
    3. C+4
    4. D−2
    ( )
  2. 2

    In the reaction H₂ + CuO → Cu + H₂O, the reducing agent is

    1. ACuO
    2. BCu
    3. CH₂O
    4. DH₂
    ( )
  3. 3

    Aqueous copper(II) sulfate is electrolysed with inert electrodes. The product at the cathode is

    1. Acopper
    2. Bhydrogen
    3. Coxygen
    4. Dsulfur dioxide
    ( )
  4. 4

    Dilute sulfuric acid is electrolysed with inert electrodes. The gas at the anode is

    1. Ahydrogen
    2. Bsulfur dioxide
    3. Coxygen
    4. Dsteam
    ( )
  5. 5

    Which change is exothermic?

    1. Amelting ice
    2. Bburning methane
    3. Cphotosynthesis
    4. Dthermal decomposition of limestone
    ( )
  6. 6

    In an energy-level diagram for an endothermic reaction, the products sit above the reactants because

    1. Aenergy is released as bonds form
    2. Bmore energy is absorbed breaking bonds than is released forming them
    3. Ca catalyst lowers the activation energy
    4. Dthe temperature of the surroundings rises
    ( )
  7. 7

    Raising the temperature increases the rate of a reaction mainly because

    1. Amore particles have energy equal to or greater than the activation energy
    2. Bthe activation energy of the reaction is lowered
    3. Cthe particles become larger
    4. Dthe frequency factor of every collision doubles
    ( )
  8. 8

    A catalyst increases the rate of a reaction by

    1. Araising the temperature of the mixture
    2. Bincreasing the concentration of the reactants
    3. Cproviding an alternative pathway of lower activation energy
    4. Dshifting the position of equilibrium to the right
    ( )
  9. 9

    In the Haber process, N₂ + 3H₂ ⇌ 2NH₃, increasing the pressure shifts the equilibrium to the right because

    1. Athe forward reaction is exothermic
    2. Bthe right-hand side has fewer gas molecules
    3. Cthe catalyst works better at high pressure
    4. Dammonia liquefies under pressure
    ( )
  10. 10

    The catalyst used in the Haber process is

    1. Avanadium(V) oxide
    2. Bnickel
    3. Cplatinum
    4. Diron
    ( )
  11. 11

    The noble gases are unreactive because their atoms

    1. Ahave full outer electron shells
    2. Bhave very small nuclei
    3. Cexist as diatomic molecules
    4. Dcontain no neutrons
    ( )
  12. 12

    Which set places the halogens in order of increasing reactivity?

    1. ACl₂, Br₂, I₂
    2. BI₂, Br₂, Cl₂
    3. CBr₂, I₂, Cl₂
    4. DI₂, Cl₂, Br₂
    ( )
  13. 13

    Across Period 3 from sodium to sulfur, the oxides change from

    1. Aacidic to basic
    2. Bamphoteric to basic
    3. Cbasic to acidic, via amphoteric
    4. Dneutral throughout
    ( )
  14. 14

    Which metal is stored under oil?

    1. Acopper
    2. Bzinc
    3. Ciron
    4. Dpotassium
    ( )
  15. 15

    Aluminium window frames resist corrosion because aluminium

    1. Aforms a protective oxide layer
    2. Bis below hydrogen in the reactivity series
    3. Cis unreactive with oxygen
    4. Dis coated with paint during manufacture
    ( )
  16. 16

    Iron rusts only when both substances are present. They are

    1. Aoxygen and carbon dioxide
    2. Bwater and carbon dioxide
    3. Coxygen and water
    4. Dwater and nitrogen
    ( )
  17. 17

    Which gas is the main contributor to the enhanced greenhouse effect among the emissions listed?

    1. Anitrogen
    2. Boxygen
    3. Cargon
    4. Dcarbon dioxide
    ( )
  18. 18

    In a catalytic converter, carbon monoxide and nitrogen oxides are converted mainly to

    1. Amethane and ammonia
    2. Bsulfur dioxide and oxygen
    3. Cozone and water
    4. Dcarbon dioxide and nitrogen
    ( )
  19. 19

    Which reagent distinguishes an alkene from an alkane?

    1. Abromine water, decolourised by the alkene
    2. Blimewater, turned milky by the alkene
    3. Cdamp red litmus, turned blue by the alkene
    4. Daqueous sodium hydroxide, precipitating with the alkene
    ( )
  20. 20

    The general formula of the carboxylic acids is

    1. ACnH2n+2
    2. BCnH2n
    3. CCnH2n+1COOH
    4. DCnH2n+1OH
    ( )

Section B: Structured questions[60 marks]

Answer all questions in the spaces provided. Show all necessary working. Give numerical answers to 3 significant figures where appropriate, with units.

  1. 1

    Zinc metal is placed in aqueous silver nitrate: Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag.

    1. (a)

      Write the ionic equation for this reaction.

      [1]
    2. (b)

      Identify the species that is oxidised and explain your answer in terms of electrons.

      [2]
    3. (c)

      Name the oxidising agent.

      [1]
    4. (d)

      Deduce the oxidation state of nitrogen in AgNO₃.

      [2]
    5. (e)

      Explain why this reaction is described as redox.

      [2]
  2. 2

    Concentrated aqueous sodium chloride (brine) is electrolysed in an industrial cell using inert electrodes.

    1. (a)

      Name the product at each electrode and write the half-equation for each reaction.

      [4]
    2. (b)

      Explain why chlorine is produced at the anode rather than oxygen in this concentrated solution.

      [2]
    3. (c)

      Sodium hydroxide is left in the solution. Describe how its presence can be shown.

      [1]
    4. (d)

      Write the overall ionic equation for the electrolysis, showing hydroxide ions among the products.

      [2]
    5. (e)

      State one industrial use of the chlorine produced.

      [1]
  3. 3

    A student burns 0.32 g of methanol, CH₃OH, in a spirit burner. The flame heats 200 g of water in a copper calorimeter and the water temperature rises by 20 °C. (Specific heat capacity of water = 4.2 J/(g °C); Mr of CH₃OH = 32)

    1. (a)

      Calculate the heat energy absorbed by the water.

      heat absorbed =kJ[2]
    2. (b)

      Calculate the moles of methanol burned.

      moles of CH₃OH =mol[1]
    3. (c)

      Hence calculate the enthalpy change of combustion of methanol from these results, giving the sign and unit.

      enthalpy change =kJ/mol[2]
    4. (d)

      State whether bond forming releases or absorbs energy.

      [1]
    5. (e)

      The same reaction is repeated with powdered fuel instead of large lumps, and the rate rises. Explain why, in terms of collisions.

      [2]
    6. (f)

      Describe how adding a catalyst changes the energy profile of the reaction.

      [2]
  4. 4

    This question is about ammonia manufacture and the Periodic Table.

    1. (a)

      State what happens to the yield of ammonia in N₂ + 3H₂ ⇌ 2NH₃ when the pressure is increased, and explain why.

      [2]
    2. (b)

      The process runs at about 450 °C even though a lower temperature would give more ammonia. Explain this compromise.

      [2]
    3. (c)

      State why the ammonia is removed as a liquid as it forms.

      [2]
    4. (d)

      Element R forms the ion R²⁺ and reacts vigorously with cold water to give hydrogen. State the group of R and write the formula of its sulfate.

      [3]
    5. (e)

      Explain why the Group I metals become more reactive down the group.

      [1]
  5. 5

    This question is about metals and air quality.

    1. (a)

      Write the equation for the reduction of iron(III) oxide by carbon monoxide in the blast furnace.

      [2]
    2. (b)

      State why limestone is added to the furnace.

      [2]
    3. (c)

      State two advantages of recycling aluminium rather than extracting it from its ore.

      [2]
    4. (d)

      Name the pollutant formed when sulfur impurities in fuels burn, and state the environmental problem it causes.

      [2]
    5. (e)

      Explain why carbon monoxide from incomplete combustion is dangerous to health.

      [2]
  6. 6

    This question is about organic chemistry.

    1. (a)

      Name the process used to separate crude oil into fractions.

      [1]
    2. (b)

      State the general formula of the alkanes.

      [1]
    3. (c)

      Write the equation for the complete combustion of propane, C₃H₈.

      [2]
    4. (d)

      Ethene is hydrated to ethanol industrially. State the reagent and conditions.

      [2]
    5. (e)

      Write the equation for the fermentation of glucose to ethanol, and state one condition.

      [2]
    6. (f)

      Ethanol reacts with ethanoic acid to form an ester. Name the ester and write the equation for the reaction.

      [2]
    7. (g)

      State the type of polymerisation that makes poly(ethene), and name the monomer.

      [1]
    8. (h)

      State one environmental problem caused by the disposal of addition polymers.

      [1]

— End of paper —