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Cambridge International Examinations

Cambridge International General Certificate of Secondary Education
*7234333226*

CHEMISTRY 0620/32
Paper 3 (Extended) October/November 2015
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.

READ THESE INSTRUCTIONS FIRST

Write your Centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use an HB pencil for any diagrams or graphs.
Do not use staples, paper clips, glue or correction fluid.
DO NOT WRITE IN ANY BARCODES.

Answer all questions.

Electronic calculators may be used.
A copy of the Periodic Table is printed on page 12.
You may lose marks if you do not show your working or if you do not use appropriate units.

At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.

The syllabus is approved for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 12 printed pages.

IB15 11_0620_32/FP
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1 Use your copy of the Periodic Table to help you answer some of these questions.

(a) Predict the formulae of the following compounds.

(i) nitrogen fluoride ..................................................................................................................

(ii) phosphorus sulfide .............................................................................................................

[2]

(b) Deduce the formulae of the following ions.

(i) selenide ..............................................................................................................................

(ii) gallium ................................................................................................................................

[2]

(c) Use the following ions to determine the formulae of the compounds.

ions OH– Cr3+ Ba2+ SO42–

compounds

(i) chromium(III) sulfate ..........................................................................................................

(ii) barium hydroxide ................................................................................................................

[2]

[Total: 6]

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2 (a) Polluted air contains two oxides of carbon and two oxides of nitrogen. A major source of these
pollutants is motor vehicles.

(i) Describe how carbon dioxide and carbon monoxide are formed in motor vehicle engines.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) State one adverse effect of each of these gases.

.............................................................................................................................................

....................................................................................................................................... [2]

(iii) Nitrogen monoxide, NO, is released by motor vehicle exhausts.

Explain how nitrogen monoxide is formed in motor vehicle engines.

.............................................................................................................................................

....................................................................................................................................... [2]

(iv) When nitrogen monoxide is released into the atmosphere, nitrogen dioxide, NO2, is formed.

Suggest an explanation why this happens.

....................................................................................................................................... [1]

(b) Predict the possible adverse effect on the environment when this non-metal oxide, NO2, reacts
with water and oxygen.

....................................................................................................................................................

.............................................................................................................................................. [2]

(c) How are the amounts of carbon monoxide and nitrogen monoxide emitted by modern motor
vehicles reduced? Include an equation in your answer.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 13]

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3 Two of the main uses of zinc are for galvanising and for making alloys.

One of the main ores of zinc is zinc blende, ZnS. There are two stages in the extraction of zinc from
this ore.

(a) Stage 1 Zinc oxide is made from zinc blende.

Describe how this is done and write a word equation for the reaction.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) Stage 2 Zinc oxide is reduced to zinc.

Write a word equation for the reduction of zinc oxide by coke.

.............................................................................................................................................. [1]

(c) The zinc produced by this process is impure. It can be purified by electrolysis using a method
which is similar to the purification of copper. Under the conditions used in the process, zinc is
the product at the negative electrode (cathode).

Complete the following description of this purification.

The electrolyte is aqueous ................................................................................................. . [1]

The negative electrode (cathode) is made of .................................................................... . [1]

The positive electrode (anode) is impure zinc.

The equation for the reaction at the cathode is ................................................................. . [1]

The equation for the reaction at the anode is .................................................................... . [1]

Explain why the concentration of the electrolyte does not change.

....................................................................................................................................................

.............................................................................................................................................. [2]

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(d) Brass is an alloy which contains zinc.

(i) Name the other metal in brass.

....................................................................................................................................... [1]

(ii) Suggest two reasons why an alloy such as brass is preferred to either of its constituent
metals.

.............................................................................................................................................

....................................................................................................................................... [2]

(e) In an experiment to investigate the rate of rusting of steel, three pieces of steel were used. One
piece of steel was completely coated with copper, one piece completely coated with zinc and
the third piece was left uncoated. All three pieces were left exposed to the atmosphere.

(i) Explain why the uncoated piece started to rust.

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) The coating on both of the other two pieces was scratched, exposing the steel.

exposed steel thin layer

does not rust of zinc

steel

The piece of steel coated with zinc still did not rust but the copper-coated piece of steel
rusted very rapidly.

Explain these observations in terms of the formation of ions and the transfer of electrons.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [4]

[Total: 17]

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4 (a) Propane reacts with chlorine to form a mixture of chloropropanes. This is a photochemical
reaction.

(i) What is meant by the phrase photochemical reaction?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) The products of this reaction include two isomers, one of which has the following structural
formula.

H H H

H C C C Cl

H H H

Draw the structural formula of the other isomer.

[1]

(iii) Explain why these two different compounds are isomers.

.............................................................................................................................................

....................................................................................................................................... [2]

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(b) Bond breaking is an endothermic change and bond forming is an exothermic change.

Bond energy is the amount of energy in kJ / mol needed to break one mole of the specified
bond.

H H H H H H

H C C C H + Cl Cl → H C C C Cl + H Cl

H H H H H H

Use the following bond energies to determine whether this reaction is exothermic or
endothermic. You must show your reasoning.

bond energies
bond
in kJ / mol
C–Cl 338
C–H 412
Cl –Cl 242
H–Cl 431
C–C 348

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

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(c) (i) Chloropropane can be hydrolysed to propanol, CH3CH2CH2OH, by sodium hydroxide.

Write the equation for this reaction.

....................................................................................................................................... [2]

(ii) Propanol can be dehydrated. It loses a water molecule to form a hydrocarbon.

Give the name and structural formula of this hydrocarbon.

name .................................................

structural formula

[2]

(iii) Propanol is oxidised to a carboxylic acid by acidified potassium manganate(VII).

Deduce the name of this acid.

....................................................................................................................................... [1]

(d) Propanol reacts with methanoic acid to form the ester propyl methanoate.

CH3CH2CH2OH + HCOOH → HCOOCH2CH2CH3 + H2O

4.0 g of methanoic acid was reacted with 6.0 g of propanol.

(i) Calculate the Mr of methanoic acid = ........................................ [1]

(ii) Calculate the Mr of propanol = ........................................ [1]

(iii) Determine which one is the limiting reagent. Show your reasoning.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(iv) Calculate the maximum yield in grams of propyl methanoate, Mr = 88.

....................................................................................................................................... [1]

[Total: 17]

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5 Iron is extracted from its ore, hematite, in a blast furnace.

Substances added to the furnace are:

• iron ore, hematite, containing impurities such as silica, SiO2
• air
• coke, C
• limestone, CaCO3

Substances formed in the blast furnace are:

• molten iron
• molten slag
• waste gases such as carbon dioxide

(a) State the two functions of the coke used in the blast furnace.

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) Write an equation for the conversion of hematite, Fe2O3, to iron.

.............................................................................................................................................. [2]

(c) Explain how the silica impurity is removed and separated from the molten iron.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

(d) The molten iron from the furnace is impure.

It contains impurities which include the element carbon.

Explain how the carbon is removed. Include an equation in your answer.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 10]

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10

6 The table below shows the elements in the third period of the Periodic Table, the number of
electrons in their outer energy level, their oxidation state in their common compounds and their
melting points.

element Na Mg Al Si P S Cl Ar
number of outer electrons 1 2 3 4 5 6 7 8
oxidation state +1 +2 +3 +4 / –4 –3 –2 –1 0
melting point / °C 98 650 660 1414 317 115 –101 –189

(a) Describe and explain the variation in oxidation state across the period.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

(b) The first three elements, Na, Mg and Al, are metals.

Describe the structure of a typical metal.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

(c) Explain why Na, Mg and Al are good conductors of electricity.

.............................................................................................................................................. [1]

(d) Which element exists as diatomic molecules of the type X2?

.............................................................................................................................................. [1]

(e) Silicon has a similar structure to diamond.

Explain why silicon has the highest melting point in the period.

....................................................................................................................................................

.............................................................................................................................................. [2]

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11

(f) Sodium chloride is a crystalline solid with a high melting point. It dissolves in water to give a
neutral solution. Phosphorus trichloride is a liquid at room temperature. It reacts with water to
form an acidic solution.

Suggest an explanation for these differences in properties.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(g) Describe how you could show that magnesium oxide is a basic oxide and not an amphoteric
oxide.

....................................................................................................................................................

.............................................................................................................................................. [2]

(h) Draw a dot-and-cross diagram showing the bonding in magnesium oxide. Show outer electrons
only.

[3]

[Total: 17]

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DATA SHEET
The Periodic Table of the Elements

the live examination series.

Group
I II III IV V VI VII 0
1 4
H He
Hydrogen Helium
1 2

7 9 11 12 14 16 19 20
Li Be B C N O F Ne
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
3 4 5 6 7 8 9 10

23 24 27 28 31 32 35.5 40
Na Mg Al Si P S Cl Ar
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
11 12 13 14 15 16 17 18

39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
12

85 88 89 91 93 96 101 103 106 108 112 115 119 122 128 127 131

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

0620/32/O/N/15
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

133 137 139 178 181 184 186 190 192 195 197 201 204 207 209

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Caesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon
55 56 57 * 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

226 227
Fr Ra Ac
Francium Radium Actinium
87 88 89

140 141 144 150 152 157 159 162 165 167 169 173 175
*58-71 Lanthanoid series
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
90-103 Actinoid series Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium
58 59 60 61 62 63 64 65 66 67 68 69 70 71
a a = relative atomic mass 232 238
Key X X = atomic symbol Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium
b b = proton (atomic) number 90 91 92 93 94 95 96 97 98 99 100 101 102 103

The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
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To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International
Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after