Prelim Practice Paper: Preliminary Examination — question paper

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

   In the reaction ZnO + C → Zn + CO, the substance that has been oxidised is

   1. AC, because it gains oxygen
   2. BZnO, because it loses oxygen
   3. CZn, because it is a metal
   4. DCO, because it is a gas
   ( )
2. 2

   The oxidation state of manganese in KMnO₄ is (K = +1, O = −2)

   1. A+5
   2. B+6
   3. C+7
   4. D+8
   ( )
3. 3

   A solution turns acidified potassium manganate(VII) from purple to colourless. The solution

   1. Agives electrons away and is itself oxidised
   2. Bgives electrons away and is itself reduced
   3. Ctakes electrons and is itself oxidised
   4. Dtakes electrons and is itself reduced
   ( )
4. 4

   Atoms of elements in the same period have the same

   1. Anumber of outer electrons
   2. Bnumber of neutrons
   3. Cmetallic character
   4. Dnumber of occupied electron shells
   ( )
5. 5

   Down Group 17, the molecular elements change from gas to liquid to solid because

   1. Atheir molecules get heavier and attract each other more strongly
   2. Btheir bonds get stronger
   3. Cthey gain electrons
   4. Dthey become metals
   ( )
6. 6

   Which displacement reaction happens?

   1. Acopper added to iron(II) sulfate solution
   2. Biron added to magnesium sulfate solution
   3. Cmagnesium added to copper(II) sulfate solution
   4. Dcopper added to magnesium sulfate solution
   ( )
7. 7

   An iron gate is coated with plastic to stop it rusting. This works because the coating

   1. Aadds a layer of oxygen
   2. Bkeeps oxygen and water away from the iron
   3. Creacts with the iron to form a hard alloy
   4. Dremoves the water already inside the iron
   ( )
8. 8

   A reaction raises the temperature of its surroundings. It is

   1. Aendothermic
   2. Bspontaneous
   3. Ccatalysed
   4. Dexothermic
   ( )
9. 9

   Which change is endothermic?

   1. Aburning natural gas
   2. Bneutralising acid with alkali
   3. Cammonium nitrate dissolving in water
   4. Dmagnesium burning in air
   ( )
10. 10

    Powdered marble reacts faster than one lump of the same mass because the powder has

    1. Amore energy per collision
    2. Ba larger surface area for collisions
    3. Ca higher temperature
    4. Da higher concentration
    ( )
11. 11

    Raising the temperature speeds a reaction up because the particles

    1. Acollide more often and with more energy
    2. Bget bigger
    3. Cbecome more concentrated
    4. Dlose electrons
    ( )
12. 12

    Aqueous bromine is added to ethene. The orange colour

    1. Astays orange
    2. Bturns purple
    3. Cdisappears
    4. Dturns blue
    ( )
13. 13

    Cracking decane, C₁₀H₂₂, can produce

    1. Aethane and propene
    2. Bethanol and ethene
    3. Coctane and hydrogen
    4. Doctane and ethene
    ( )
14. 14

    Ethanol is made industrially from sugar by fermentation. The essential organism and condition are

    1. Abacteria, strong sunlight
    2. Byeast, absence of air and about 35 °C
    3. Cyeast, pure oxygen and 100 °C
    4. Dmoulds, freezing temperatures
    ( )
15. 15

    Ethanol is oxidised to

    1. Aethene
    2. Bethane
    3. Cethanoic acid
    4. Dethane-1,2-diol
    ( )
16. 16

    Poly(ethene) is formed from ethene by

    1. Ajoining single-bonded alkane molecules end to end
    2. Baddition polymerisation of C=C bonds
    3. Csubstitution with chlorine
    4. Dcracking large alkanes
    ( )
17. 17

    The percentage of oxygen in clean, dry air is about

    1. A78%
    2. B0.04%
    3. C1%
    4. D21%
    ( )
18. 18

    Which pair lists a source with its correct pollutant?

    1. Alightning — sulfur dioxide
    2. Bengines — oxides of nitrogen
    3. Crice paddies — carbon monoxide
    4. Dvolcanoes — ozone
    ( )
19. 19

    Carbon monoxide is dangerous because it

    1. Aburns the skin
    2. Berodes limestone
    3. Cturns litmus red
    4. Dbinds to haemoglobin so blood carries less oxygen
    ( )
20. 20

    Which process removes carbon dioxide from the atmosphere?

    1. Acombustion
    2. Brespiration
    3. Cphotosynthesis
    4. Ddecay
    ( )

Section B: Structured questions[60 marks]

Answer all questions in the spaces provided. Show all necessary working.

1. 1

   This question is about redox reactions.

   1. (a)

      Define oxidation in two ways: in terms of oxygen and in terms of electrons.

      [2]
   2. (b)

      Determine the oxidation state of nitrogen in potassium nitrate, KNO₃ (K = +1, O = −2).

      oxidation state =[2]
   3. (c)

      Iodide ions are oxidised to iodine by hydrogen peroxide in acid solution. Describe the test that confirms iodine has formed.

      [2]
   4. (d)

      Explain, in electron terms, why the iodide ion is the reducing agent in (c).

      [4]
2. 2

   This question is about the reactivity series and rusting.

   1. (a)

      Metal P fizzes slowly in dilute hydrochloric acid; metal Q does not react at all; metal R fizzes faster than P. P displaces Q from its salt solution. Arrange P, Q, R in order of reactivity (most reactive first) and justify each comparison.

      [4]
   2. (b)

      State where hydrogen sits relative to Q in the reactivity series, given that Q does not react with dilute acid.

      [2]
   3. (c)

      A ship's iron hull is protected by painting and by attaching magnesium blocks. State why each works.

      [4]
3. 3

   This question is about energetics and rates.

   1. (a)

      Sodium hydrogencarbonate is added to citric acid solution. The temperature falls from 22.0 °C to 17.5 °C. State the type of energy change and explain your answer.

      [2]
   2. (b)

      Give one exothermic change used in everyday life and one use of an endothermic change.

      [2]
   3. (c)

      Excess marble chips react with 50 cm³ of 1.0 mol/dm³ hydrochloric acid at 20 °C. Sketch-in-words and explain the volume–time graph: describe its shape from start to finish.

      [4]
   4. (d)

      The experiment is repeated with 2.0 mol/dm³ acid at 20 °C. State two differences in the graph and one thing that stays the same.

      [4]
4. 4

   This question is about organic chemistry.

   1. (a)

      State what the fraction called naphtha is, give one use of it, and name the process that separates it from crude oil.

      [3]
   2. (b)

      Dodecane, C₁₂H₂₆, is cracked. It forms one molecule of ethene and one other hydrocarbon. Write the equation and state how the other product is identified as an alkane or alkene.

      [5]
   3. (c)

      A polymer)s repeat unit is –CH₂–CH(CH₃)–. Draw-in-words its monomer and name the polymerisation type.

      [3]
   4. (d)

      State two problems caused by discarded poly(ethene) and one advantage of chemical recycling over physical recycling.

      [3]
5. 5

   This question is about air quality.

   1. (a)

      Calculate the volume of nitrogen and of oxygen in a 750 cm³ sample of clean, dry air.

      nitrogen = ...... cm³; oxygen =cm³[3]
   2. (b)

      A city)s morning air contains raised CO and NOₓ. State the source chemistry of each pollutant.

      [4]
   3. (c)

      Explain how SO₂ from a power station damages (i) human health and (ii) a marble statue nearby.

      [4]
   4. (d)

      Atmospheric CO₂ has risen steadily for a century. Explain why, using two named human activities and the carbon-cycle processes involved, and state one consequence.

      [3]