Chemistry 0620/32 May/June 2021: question paper and mark scheme
Cambridge IGCSE Chemistry (0620), Paper 3 Theory (Core), May/June 2021. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) The electronic structures of five atoms, A, B, C, D and E, are shown.
A B C D E
Answer the following questions about these electronic structures.
Each electronic structure may be used once, more than once or not at all.
State which electronic structure, A, B, C, D or E, represents:
(i) an atom in Group III of the Periodic Table
. …… [1]
(ii) an atom of a noble gas
. …… [1]
(iii) an atom that forms a stable ion with a single positive charge
. …… [1]
(iv) an atom that contains only two shells of electrons
. …… [1]
(v) an atom with a proton number of 16.
. …… [1]
(b) Complete the table to show the number of electrons, neutrons and protons in the silicon atom and sodium ion shown.
number of number of number of electrons neutrons protons
14Si
30
14
11Na
23 +
12
[3]
[Total: 8]
Mark scheme
1(a)(i) B 1
1(a)(ii) D 1
1(a)(iii) A 1
1(a)(iv) B 1
1(a)(v) C 1
1(b) number of electrons in Na ion =10 (1) 3
number of neutrons in Si = 16 (1)
number of protons in Si = 14
AND
number of protons in Na ion = 11 (1)
The table shows the masses of some of the ions in 1000 cm3 of fruit juice.
mass of ion in 1000 cm3 name of ion formula of ion of fruit juice / mg ammonium NH4+ 15
Ca2+ 71 chloride Cl – 135 magnesium Mg2+ 160 nitrate NO3– 2 phosphate PO43– 63 potassium K+ 184 sodium Na+ 3
SO42– 85
(a) Answer these questions using only the information in the table.
(i) State which positive ion has the lowest mass in 1000 cm3 of fruit juice.
. …… [1]
(ii) Give the formulae of the ions in calcium sulfate.
…… and . …… [1]
(iii) Calculate the mass of magnesium ions in 250 cm3 of fruit juice.
mass = …… mg [1]
(b) Describe a test for calcium ions.
test . ……
observations ……
[2]
(c) Ammonium ions, NH4+, are present in most fertilisers. Ammonium ions contain nitrogen.
Name two other elements present in most fertilisers.
1 ……
2 ……
[2]
(d) A student heated a mixture of ammonium chloride and sodium hydroxide in a test‑tube.
NH4Cl + NaOH → NH3 + NaCl + H2O
mixture of ammonium chloride and sodium hydroxide
heat
Pungent-smelling ammonia gas is given off.
Describe one other observation that can be made.
…… [1]
(e) Ammonia reacts with chlorine.
Complete the equation for this reaction.
……NH3 + ……Cl 2 → N2 + 6HCl[2]
(f) A small beaker of aqueous ammonia is placed at the front of a classroom.
At first, the students at the back of the class do not smell the ammonia gas.
After a short time, the students at the back of the class smell the ammonia.
Explain these observations using the kinetic particle model.
…… [3]
[Total: 13]
Mark scheme
2(a)(i) Na + / sodium 1
2(a)(ii) Ca2+ AND SO42- 1
2(a)(iii) 40 (mg) 1
2(b) (add aqueous) sodium hydroxide (1) 2
white precipitate (1)
OR
( add aqueous) ammonia (1)
no precipitate / very slight white precipitate (1)
2(c) potassium (1) 2
phosphorus (1)
2(d) colourless liquid (condenses at the mouth of the tube) 1
2(e) 2 (NH3) (1) 2
3 (Cl2) (1)
2(f) 1 mark each for any 3 of: 3
• evaporation of ammonia molecules (from the solution) / (ammonia) molecules escape from solution
• diffusion
• molecules in (constant) movement / molecules collide / molecules travel
• (movement of) molecules is random / in every direction / haphazard
• molecules spread out / molecules mix
• (smell occurs when) molecules hit (the sensory cells in) the nose
• (molecules spread) from higher concentration to lower concentration
The table shows some properties of four halogens.
melting point boiling point density of liquid at element colour
/ °C / °C boiling point in g / cm3
chlorine –101 –35 1.56 light green
bromine –7 3.12 red-brown
iodine 114 184 dark grey
astatine 302 337 6.35 black
(a) (i)
Complete the table by predicting:
● the boiling point of bromine
● the density of liquid iodine at its boiling point.
[2]
(ii) Describe the trend in the depth of colour of the halogens down the group.
. …… [1]
(iii) Deduce the state of chlorine at –50 °C.
Explain your answer.
. ……
. ……
. …… [2]
(b) The halogens have molecules that are diatomic.
Explain the meaning of the term diatomic.
…… [1]
(c) Astatine is a radioactive element. One isotope of astatine has a nucleon number of 209.
(i) Define nucleon number.
. …… [1]
(ii) State one medical use of radioactive isotopes.
. …… [1]
(iii) The isotope 235U is also radioactive.
State the major use of this isotope of uranium.
. …… [1]
[Total: 9]
Mark scheme
3(a)(i) boiling point of Br any values between – 5 and 180 (°C) (inclusive of these values) (1) 2
density of I: any values between 3.5 and 6.0 (nm) (inclusive of these values) (1)
3(a)(ii) increases (1) 1
3(a)(iii) liquid (1) 2
–50 (°C) is between the melting point and boiling point / the melting point is lower than –50 (°C) AND the boiling point is
above –50 (°C) (1)
3(b) (molecule) made up of two atoms 1
3(c)(i) number of protons plus neutrons (in the nucleus of an atom) 1
3(c)(ii) cancer treatment / tracer (e.g. for thyroid function) 1
3(c)(iii) source of energy / energy production 1
The structure of succinic acid is shown.
O
H
C
H C O H
H C O H
C
H
O
(a) (i) On the structure draw a circle around one carboxylic acid functional group. [1]
(ii) Deduce the formula of succinic acid to show the number of carbon, hydrogen and oxygen atoms.
. …… [1]
(b) When succinic acid is heated it undergoes sublimation.
State the meaning of the term sublimation.
…… [1]
(c) Succinic acid is heated with compound F.
Compound F has the formula HOCH2CH2OH.
(i) State the name of the –OH functional group in compound F.
. …… [1]
(ii) A polymer is formed when succinic acid is heated with compound F.
Choose one word from the list that best describes the small molecules that react together to form a polymer.
Draw a circle around the correct answer.
bases ceramics monomers plastics[1]
(d) Ethanoic acid is also a carboxylic acid.
Describe the observations made when ethanoic acid reacts with:
blue litmus paper ……
calcium carbonate. ……
[2]
(e) A student’s graph of how the pH changes when aqueous sodium hydroxide is added slowly to dilute ethanoic acid is shown.
14
12
10
8
pH
6
4
2
0
0 10 20 30 40 volume of aqueous sodium hydroxide / cm3
(i) Deduce the pH of the dilute ethanoic acid before the addition of aqueous sodium hydroxide.
pH = …… [1]
(ii) Deduce the volume of aqueous sodium hydroxide added when the pH is neutral.
…… cm3 [1]
[Total: 9]
Mark scheme
4(a)(i) COOH circled 1
4(a)(ii) C4H6O4 1
4(b) conversion of vapour directly to solid / conversion of solid directly to vapour 1
4(c)(i) alcohol 1
4(c)(ii) monomers 1
4(d) blue litmus paper: (turns) red (1) 2
calcium carbonate: bubbles / fizzes / effervescence / calcium carbonate reduces in size (1)
4(e)(i) pH 4.8 1
4(e)(ii) 22 (cm3) 1
(a) Calcium carbonate is heated in a closed container.
CaCO3 CaO + CO2
(i) State the name of a rock which is mainly calcium carbonate.
. …… [1]
(ii) State the meaning of the symbol .
. …… [1]
(iii) CaO is lime. Lime is used for neutralising acidic industrial waste.
Give one other use of lime.
. …… [1]
(iv) Describe a test for carbon dioxide.
test . ……
observations ……
[2]
(b) Carbon dioxide is produced when dilute hydrochloric acid reacts with calcium carbonate.
CaCO3 + 2HCl → CaCl 2 + CO2 + H2O
(i) Complete the diagram to show the apparatus used to investigate the volume of carbon dioxide produced during this reaction.
gas syringe
[2]
(ii) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate.
● The temperature is decreased.
All other conditions stay the same.
. ……
● Calcium carbonate powder is used instead of large pieces of calcium carbonate.
All other conditions stay the same.
. ……
[2]
(c) Carbon dioxide is also formed when the hydrocarbon C4H8 is completely combusted.
(i) The hydrocarbon C4H8 is an alkene.
Complete the structure of this alkene by adding the missing bonds and atom.
H H H
H C C C C
H H H
[2]
(ii) The incomplete combustion of C4H8 produces carbon monoxide.
State the meaning of the term incomplete combustion.
. ……
. …… [1]
[Total: 12]
Mark scheme
5(a)(i) limestone 1
5(a)(ii) reversible (reaction) 1
5(a)(iii) neutralising (acidic) soil / making cement / steelmaking 1
5(a)(iv) limewater (1) 2
turns milky / goes cloudy / white precipitate (1)
5(b)(i) flask or other suitable container (1) 2
connecting tubing AND apparatus gas-tight / no air gaps (1)
5(b)(ii) lower temperature: (rate) decreases / (rate) lower (1) / (rate) slower 2
powdered CaCO3: (rate) increases / (rate) higher (1) / (rate) faster
5(c)(i) double bond between 3rd and 4th C atoms from left (1) 2
─ H connected to 4th carbon from the left (1)
5(c)(ii) (combustion with) limited oxygen / the hydrocarbon is in excess (1) 1
This question is about air and gases.
(a) (i) State the percentage of oxygen in clean, dry air.
…… % [1]
(ii) Name two other elements in clean, dry air.
…… and . …… [2]
(b) Lead and sulfur dioxide are pollutants of air.
For each of these pollutants state the source of the pollutant and an adverse effect of the pollutant.
source of lead ……
adverse effect ……
source of sulfur dioxide ……
adverse effect ……
[4]
(c) Water is present in the atmosphere.
(i) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of water.
[2]
(ii) Anhydrous copper(II) sulfate is used to test for water.
State the colour change in this test.
from …… to …… [2]
[Total: 11]
Mark scheme
6(a)(i) 21% 1
6(a)(ii) nitrogen (1) 2
argon / other noble gases (1)
6(b) lead 4
source: (some forms of) petrol / (some old) paints (1)
adverse effect: harms nervous system / brain (of children) (1)
sulfur dioxide
source: burning fossil fuels (1)
adverse effect: breathing difficulties / irritates eyes / irritates nose / irritates throat / irritates lungs / asthma
6(c)(i) pair of electrons between each H and the O atom and no other electrons on the H (1) 2
four non-bonding electrons on the oxygen atom (1)
6(c)(ii) (from) white (1) 2
(to) blue (1)
(a) Dilute sulfuric acid is electrolysed using carbon electrodes.
State the products of this electrolysis at:
the negative electrode ……
the positive electrode. ……
[2]
(b) Graphite is a form of carbon. Graphite has a giant structure with covalent bonds.
(i) State the meaning of the term covalent bond.
. ……
. …… [2]
(ii) Graphite is a solid.
Describe the arrangement and motion of the particles in a solid.
arrangement ……
. ……
motion . ……
. ……
[2]
(c) Graphite is one form of solid carbon.
Name one other form of solid carbon.
…… [1]
[Total: 7]
Mark scheme
7(a) negative electrode: hydrogen (1) 2
positive electrode: oxygen (1)
7(b)(i) shared pair of electrons (2) 2
If 2 marks not scored 1 mark for:
pair of electrons OR shared electrons
7(b)(ii) arrangement: regular / in hexagons (1) 2
motion: (only) vibrating (1)
7(c) diamond 1
This question is about elements in the Periodic Table.
(a) The table shows some properties of five elements, P, Q, R, S and T.
melting point density electrical conductivity atomic radius element
/ °C in g / cm3 of the solid / nm
P 63 0.86 very good 0.235
Q –7 3.12 does not conduct 0.114
R 839 1.54 very good 0.174
S 1495 8.9 very good 0.126
T –157 0.0035 does not conduct 0.110
Use only the elements shown in the table to answer this question.
State which two of the elements, P, Q, R, S and T, are covalent molecules.
Give two reasons for your answer.
elements …… and ……
reason 1 ……
reason 2 ……
[3]
(b) Describe how the metallic character of the elements depends on their position in the Periodic
Table.
…… [1]
(c) Potassium is an element in Group I of the Periodic Table. Cobalt is a transition element.
Cobalt has a higher density than potassium.
Give two other ways in which the properties of transition elements differ from the properties of
Group I elements.
1 ……
2 ……
[2]
(d) State whether potassium oxide is a basic oxide or an acidic oxide.
Give a reason for your answer.
…… [1]
(e) The table compares the ease of reduction of four metal oxides when heated with carbon.
metal oxide details of reduction chromium(III) oxide reduced at 1200 °C manganese(IV) oxide reduced at 1400 °C potassium oxide not reduced at 1400 °C zinc oxide reduced at 850 °C
Put the four metals in order of their reactivity.
Put the least reactive metal first.
least reactive most reactive
[2]
(f) Describe how aqueous sodium hydroxide is used to test for chromium(III) ions, Cr3+.
…… [2]
[Total: 11]
The Periodic Table of Elements
Group
I II III IV V VI VII VIII
1 2
H He hydrogen helium
Key 1 4
3 4 atomic number 5 6 7 8 9 10
Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon
7 9 relative atomic mass 11 12 14 16 19 20
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
23 24 27 28 31 32 35.5 40
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
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
39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
16
rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
85 88 89 91 93 96 – 101 103 106 108 112 115 119 122 128 127 131
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
133 137 178 181 184 186 190 192 195 197 201 204 207 209 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 114 116 actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium flerovium livermorium
– – – – – – – – – – – – –
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
139 140 141 144 – 150 152 157 159 163 165 167 169 173 175
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232 231 238 – – – – – – – – – – –
The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
Mark scheme
8(a) Q and T (1) 3
low melting point (1)
does not conduct (electricity) (1)
8(b) metallic character decreases across a period / metals are on the left (of the Periodic Table) 1
8(c) 1 mark each for any 2 of: 2
• transition elements have a high(er) melting point / Group I has a low(er) melting point
• transition elements form coloured compounds / Group I compounds are not coloured
• transition elements forms ions with different charges / Group 1 forms only one type of ion
• transition elements are good catalysts / Group 1 elements not catalysts
8(d) basic (oxide) AND potassium is a metal / metals form basic oxides/ metal oxides are basic 1
8(e) zinc < chromium < manganese < potassium (2) 2
if 2 marks not obtained:
1 mark for: one consecutive pair reversed / potassium < manganese < chromium < zinc
8(f) green precipitate (when NaOH added) (1) 2
dissolves in excess (NaOH) (1)
Checked your answers against these? Let AI mark the whole paper, on your own working.
Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.
Check your answers against it
Done this paper? Upload your script and CIE Buddy's AI marker marks it question by question against this exact scheme, puts the ticks on your own working and says what each lost mark needed.
Where can I find the 0620/32 May/June 2021 mark scheme?+
On this page, free: the mark scheme for IGCSE Chemistry 0620/32, May/June 2021 (0620_s21_ms_32), and the question paper (0620_s21_qp_32), to read or download, with each question's marking points written out underneath.
How many marks is 0620/32 out of?+
Chemistry 0620/32 for May/June 2021 is out of 80 marks, across 8 questions.
Can I get my 0620/32 answers marked?+
Yes. Upload your answers to 0620/32/M/J/21 as a PDF or photos, and CIE Buddy marks every question against this paper's official mark scheme, using Cambridge's marking rules. You get your score, each lost mark explained on your own script, and the topics to revise. It's a guide, not an official Cambridge grade.