Chemistry 0620/41 October/November 2022: question paper and mark scheme
Cambridge IGCSE Chemistry (0620), Paper 4 Theory (Extended), October/November 2022. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
The names of the elements of Period 2 of the Periodic Table are shown.
lithium beryllium boron carbon nitrogen oxygen fluorine neon
Answer the following questions about these elements.
Each element may be used once, more than once or not at all.
Identify the element which:
(a) is a product of photosynthesis
. …… [1]
(b) has an oxide found in clean, dry air
. …… [1]
(c) forms a basic oxide with the formula X2O
. …… [1]
(d) is a main component of fertilisers used to improve crop growth
. …… [1]
(e) has the highest rate of diffusion at room temperature
. …… [1]
(f) produces a red flame in a flame test
. …… [1]
(g) has only 5 electrons in each of its atoms
. …… [1]
(h) has an oxide responsible for acid rain.
. …… [1]
[Total: 8]
Potassium is a Group I element.
(a) Name and describe the bonding in potassium.
name . ……
description ……
. ……
. ……
. ……
[4]
(b) Potassium combines with sulfur to form an ionic compound, potassium sulfide, K2S.
(i) Give two physical properties of ionic compounds.
1 . ……
2 . ……
[2]
(ii) Complete the dot-and-cross diagram to show the electron arrangement and charges of the ions in potassium sulfide.
K S
K
[3]
(c) When potassium is added to water, it reacts vigorously and a coloured flame is seen.
The equation for the reaction is shown.
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
(i) State the colour of the flame seen.
. …… [1]
(ii) The solution formed is potassium hydroxide, a strong alkali.
State the formula of the ion responsible for alkalinity in a solution.
. …… [1]
(iii) State the colour of litmus in a strong alkali.
. …… [1]
(iv) Calculate the volume, in cm3, of hydrogen gas formed when 2.34 g of potassium is added to excess water at room temperature and pressure.
Use the following steps.
● Calculate the number of moles of potassium added.
= …… mol
● Determine the number of moles of hydrogen gas formed.
= …… mol
● Calculate the volume of hydrogen gas formed.
volume = …… cm3
[3]
(d) Aqueous potassium hydroxide reacts with a dilute acid to produce aqueous potassium chloride,
KCl (aq), which is a salt.
(i) Name the dilute acid used.
. …… [1]
(ii) State the type of reaction taking place.
. …… [1]
(iii) Name the experimental technique used when salts are made by reacting a dilute acid with an aqueous alkali.
. …… [1]
(e) When aqueous silver nitrate, AgNO3(aq), is added to aqueous potassium chloride, a precipitate is formed.
(i) State the colour of the precipitate formed.
. …… [1]
(ii) Name the precipitate formed.
. …… [1]
(iii) Write the ionic equation for the reaction. Include state symbols.
. …… [3]
[Total: 23]
Mark scheme
2(a) M1 metallic (1) 4
M2 lattice of potassium ions (1)
M3 sea of electrons (1)
M4 attraction between potassium ions and electrons (1)
2(b)(i) any two (one from each bullet point) 2
• physical constants: high boiling point / melting point
• conductivity: conduct electricity when aqueous / conduct electricity when molten
• solubility: soluble in water
2(b)(ii) M1 eight dots in third shell of both K (1) 3
M2 six crosses and two dots in third shell of S (1)
M3 ‘+’ charge on each K on correct answer line and ‘2–‘ charge on S ion on correct answer line (1)
2(c)(i) lilac 1
2(c)(ii) OH– 1
2(c)(iii) blue 1
2(c)(iv) M1 mol of K = 2.34 / 39 = 0.06(00) (1) 3
M2 mol of H2 = 0.06 / 2 = 0.03(00) (1)
M3 volume of H2 = 0.03 × 24 000 = 720 cm3 (1)
2(d)(i) hydrochloric (acid) 1
2(d)(ii) neutralisation 1
2(d)(iii) titration 1
2(e)(i) white 1
2(e)(ii) silver chloride 1
2(e)(iii) Ag+(aq) + Cl –(aq) → AgCl(s) 3
M1 AgCl (as only product) (1)
M2 Ag+ and Cl– (as only reactants) (1)
M3 state symbols (1)
Ammonia is made in an industrial process starting with nitrogen. The equation for the reaction is shown.
N2 + 3H2 2NH3
(a) Name the industrial process used to make ammonia.
. …… [1]
(b) State the raw material from which nitrogen is obtained.
. …… [1]
(c) State what is meant by the symbol .
. …… [1]
(d) State the temperature and pressure used in this industrial process.
temperature = …… °C
pressure = …… atm
[2]
(e) Name the catalyst used in this industrial process.
. …… [1]
(f) The forward reaction is exothermic.
State the effect, if any, on the position of the equilibrium when the following changes are made.
Explain your answers.
temperature is reduced
. ……
. ……
pressure is reduced
. ……
. ……
[4]
(g) Explain, in terms of particles, what happens to the rate of reaction when the temperature is reduced.
. ……
. ……
. ……
. ……
. …… [3]
(h) Give the formula of the compound formed when sulfuric acid reacts with ammonia.
. …… [1]
[Total: 14]
Mark scheme
3(a) Haber (process) 1
3(b) air 1
3(c) reversible 1
3(d) 450 (1) 2
200 (1)
3(e) Iron / Fe 1
3(f) reduced temperature: 4
M1 (position of) equilibrium moves to right-hand side (1)
M2 reaction is exothermic (1)
reduced pressure:
M3 (position of) equilibrium moves to left-hand side (1)
M4 more (gaseous) moles on left hand side (1)
3(g) M1 rate decreases and particles have less energy (1) 3
M2 less collisions (between particles) occur per second / per unit time (1)
M3 less of the particles/collisions have energy equal to or above the activation energy (1)
or
less of the particles / collisions have sufficient energy to react
or
a lower percentage / proportion / fraction of collisions (of particles)
• are successful or
• have energy equal to or above activation energy
3(h) (NH4)2SO4 1
A student prepares calcium nitrate, Ca(NO3)2, by adding calcium carbonate to dilute nitric acid.
(a) Write the chemical equation for this reaction.
. …… [2]
(b) Describe two observations during this reaction.
1 . ……
2 . ……
[2]
(c) The student continues to add calcium carbonate until it is in excess. The student then removes the excess calcium carbonate by filtration and collects the aqueous calcium nitrate.
State the general term given to a solution collected from filtration.
. …… [1]
(d) The student gently heats the aqueous calcium nitrate until the solution is saturated.
(i) Suggest what is meant by the term saturated solution.
. ……
. …… [2]
(ii) Describe how crystals are produced from a hot saturated solution.
. …… [1]
(e) Calcium nitrate crystals are hydrated and have the formula Ca(NO3)2•xH2O where x is a whole number of molecules of water.
The student heats the crystals to remove the molecules of water.
Ca(NO3)2•xH2O(s) → Ca(NO3)2(s) + xH2O(g)
(i) State the term used to describe the calcium nitrate after the molecules of water have been removed.
. …… [1]
(ii) The student heats a sample of Ca(NO3)2•xH2O and forms 2.46 g of Ca(NO3)2 and
0.0600 moles of H2O.
Determine the value of x. Use the following steps.
● Calculate the Mr of Ca(NO3)2.
Mr = ……
● Determine the number of moles of Ca(NO3)2 formed.
moles of Ca(NO3)2 formed = ……
● Determine the value of x in Ca(NO3)2•xH2O.
x = ……
[3]
(f) Nitrates decompose on heating.
Write the chemical equation for the reaction when solid sodium nitrate is heated.
. …… [2]
[Total: 14]
Mark scheme
4(a) CaCO3 + 2HNO3 → Ca(NO3)2 + H2O + CO2 2
M1 H2O and CO2 as product (1)
M2 rest of equation correct (1)
4(b) M1 fizzing / effervescence (1) 2
M2 solid disappears / dissolves (1)
4(c) filtrate 1
4(d)(i) M1 a solution that can contain no more solute (1) 2
M2 at a given temperature (1)
4(d)(ii) cool the solution 1
4(e)(i) anhydrous 1
4(e)(ii) M1 Mr Ca(NO3)2 = 164 (1) 3
M2 mol Ca(NO3)2 = 2.46 / 164 = 0.015(00) (1)
M3 0.015(00) / 0.015(00) = 1
0.0600 / 0.015(00) = 4 and x = 4 (1)
4(f) 2NaNO3 → 2NaNO2 + O2 2
M1 NaNO2 on the right-hand side
M2 equation completely correct
Ethene is an alkene which reacts with bromine as shown in the equation.
C2H4 + Br2 → C2H4Br2
(a) Write the general formula of alkenes.
. …… [1]
(b) Describe the colour change seen when ethene is bubbled through aqueous bromine.
from …… to …… [1]
(c) In this reaction only one product is formed from two reactants.
Name this type of organic reaction.
. …… [1]
(d) Part of the energy profile diagram of this reaction is shown.
C2H4 + Br2 energy
progress of reaction
(i) The reaction is exothermic.
Complete the energy profile diagram for this reaction.
Include:
● the position of the products
● an arrow to show the activation energy, labelled as A
● an arrow to show the energy change for the reaction.
[3]
(ii) The chemical equation for the reaction can be represented as shown.
H H H H
C C + Br Br Br C C Br
H H H H
Some bond energies are given.
bond energy bond
/ kJ mol
C–H 410
C=C 610
Br–Br 190
C–C 350
C–Br 290
Use the bond energies in the table to calculate the energy change in this reaction.
Use the following steps.
● Calculate the energy needed to break bonds.
energy = …… kJ
● Calculate the energy released in making bonds.
energy = …… kJ
● Determine the energy change in this reaction.
energy change in this reaction = …… kJ / mol
[3]
[Total: 9]
Mark scheme
5(a) CnH2n 1
5(b) orange to colourless 1
5(c) addition 1
5(d)(i) M1 horizontal line below energy level to right hand side of reactants line and labelled C2H4Br2 (1) 3
M2 activation energy ‘hump’ with upward arrow labelled A from the reactants level (1)
M3 one downward arrow starting from the energy level of the reactants and finishing at the energy level of the products (1)
5(d)(ii) M1 energy needed to break bonds 3
4 × C–H + C=C + Br–Br = 4 × 410 + 610 + 190 = 2440 (kJ) (1)
M2 energy released in making bonds
4 × C–H + C–C + 2 × C–Br = 4 × 410 + 350 + 2 × 290 = 2570 (kJ) (1)
M3 energy change M1 – M2 = – 130 (kJ / mol) (1)
Ester Y has the structure shown.
O H
H C O C H
H
(a) (i) Name ester Y.
. …… [1]
(ii) Deduce the empirical formula of ester Y.
. …… [1]
(b) Complete the dot-and-cross diagram to show the arrangement of electrons in a molecule of ester Y.
O
H
H C O C H
H
[3]
(c) Ester Y can be made by reacting two organic compounds together.
Name the compounds and draw their structures.
Show all of the atoms and all of the bonds.
name ……
structure
name ……
structure
[4]
(d) (i) Describe what is meant by the term structural isomer.
. ……
. …… [2]
(ii) Name a carboxylic acid which is a structural isomer of ester Y.
. …… [1]
[Total: 12]
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 rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
16
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
6(a)(i) methyl methanoate 1
6(a)(ii) CH2O 1
6(b) M1 all single bonding dot and cross pairs correct (1) 3
M2 double C=O bond dot and cross pairs are correct (1)
M3 complete diagram is correct (1)
6(c) M1 methanoic acid (1) 4
M2 structure of methanoic acid (1)
M3 methanol (1)
M4 structure of methanol (1)
6(d)(i) M1 same (molecular) formula (1) 2
M2 different structural formula (1)
6(d)(ii) ethanoic acid 1
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Chemistry 0620/41 for October/November 2022 is out of 80 marks, across 6 questions.
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