IGCSE Chemistry (0620) — October–November 2024, Paper 21

40 questions · every question answerable online with instant point-by-point AI marking against the official mark scheme.

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Question 1 · 1 mark · States of matter

Which row describes the arrangement and motion of the particles in a liquid? arrangement motion --- --- --- A random and particles are touching moving slowly B random with space…

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Question 2 · 1 mark · Diffusion (relative molecular mass)

Which gas has the lowest rate of diffusion at room temperature and pressure? A the gas produced when ammonium chloride is heated with aqueous sodium hydroxide B the gas which…

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Question 3 · 1 mark · Atomic structure

Which diagram represents one helium atom? (Four atom diagrams A-D are shown with a key: proton, neutron, electron. The correct diagram has 2 protons and 2 neutrons in the nucleus…

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Question 4 · 1 mark · Ionic bonding (lattice)

The diagram shows part of an ionic lattice structure, a regular grid alternating + and - ions in a 1:1 ratio. Which compound does the diagram represent? A potassium bromide B…

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Question 5 · 1 mark · Covalent bonding

Which statement about nitrogen molecules and ethene molecules is correct? A A nitrogen molecule has 2 more shared electrons than an ethene molecule. B An ethene molecule has 3…

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Question 6 · 1 mark · Simple molecular structures

Sulfur is a simple molecule with the formula S8. Which row describes and explains the melting point of sulfur? melting point explanation --- --- --- A high the covalent bonds…

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Question 7 · 1 mark · Giant covalent structures

Which row identifies a property and an explanation of the property for both diamond and silicon(IV) oxide? property explanation of property --- --- --- A very hard diamond has a…

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Question 8 · 1 mark · Metallic bonding

Which statement about the structure of metals explains why metals are malleable? A The electrons can move freely throughout the lattice. B The layers of metal ions can slide over…

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Question 9 · 1 mark · Stoichiometry (formulae)

What is the formula of iron(III) oxide? A FeO B Fe3O4 C FeO2 D Fe2O3

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Question 10 · 1 mark · Stoichiometry (percentage yield)

Calcium carbonate is heated. Calcium oxide and carbon dioxide gas are formed. The equation for the reaction is shown. CaCO3 - CaO + CO2 225 kg of calcium carbonate is heated until…

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Question 11 · 1 mark · Electrolysis

The apparatus used for electrolysis is shown (a d.c. power supply connected via + and - to two electrodes dipping in an electrolyte). Which statement is correct? A Copper forms at…

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Question 12 · 1 mark · Electrolysis (copper(II) sulfate)

Which statement about the electrolysis of aqueous copper(II) sulfate is correct? A When copper electrodes are used, the solution turns from blue to colourless. B When graphite…

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Question 13 · 1 mark · Hydrogen-oxygen fuel cells

Which statement describes an advantage of using a hydrogen-oxygen fuel cell in a car compared to a gasoline engine? A The hydrogen is difficult to store. B The hydrogen is highly…

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Question 14 · 1 mark · Energetics (activation energy)

Two reaction pathway diagrams are shown, each with arrows A and B (first diagram) and C and D (second diagram) marking energy changes. Which arrow represents the activation energy…

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Question 15 · 1 mark · Haber process

Which statements about the Haber process are correct? 1 A high temperature is used because the reaction is slow at room temperature. 2 A high pressure is used because there are…

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Question 16 · 1 mark · Contact process (sulfuric acid)

Which substance is a raw material used to manufacture sulfuric acid? A vanadium(V) oxide B sulfur C sulfur dioxide D sulfur trioxide

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Question 17 · 1 mark · Acids and bases (indicators)

Which colours are seen when litmus and methyl orange are added to separate samples of aqueous sodium hydroxide? litmus methyl orange --- --- --- A blue orange B blue yellow C…

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Question 18 · 1 mark · Oxides (acidic/basic)

Information about the solubility in water of four oxides is shown. Which oxide, when added to water, gives a solution with a pH less than pH 7? name of oxide solubility in water…

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Question 19 · 1 mark · Preparation of salts

Copper(II) sulfate is made when copper(II) carbonate reacts with dilute sulfuric acid. CuCO3 + H2SO4 - CuSO4 + H2O + CO2 Pure copper(II) sulfate crystals are obtained. Which…

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Question 20 · 1 mark · Periodic Table (Group trends)

Which statement about elements in Group I or Group VII of the Periodic Table is correct? A Bromine reacts with potassium chloride to produce chlorine. B Iodine is a monatomic…

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Question 21 · 1 mark · Group VII elements

Some information about an element from Group VII of the Periodic Table is shown: melting point -7 °C, boiling point 59 °C. What is the element? A fluorine B chlorine C bromine D…

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Question 22 · 1 mark · Transition elements

Manganese(IV) oxide, MnO2, is a black solid. The equation for the reaction between manganese(IV) oxide and dilute hydrochloric acid is shown. MnO2 + 4HCl - MnCl2 + 2H2O + Cl2 The…

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Question 23 · 1 mark · Corrosion (sacrificial protection)

Part of a steel ship is protected from rusting using a sacrificial metal. What is a suitable sacrificial metal? A copper B zinc C silver D potassium

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Question 24 · 1 mark · Uses of metals

Which row gives a use for the named metal and two properties which both explain this use? metal use property 1 property 2 --- --- --- --- --- A aluminium aircraft construction…

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Question 25 · 1 mark · Extraction of aluminium (electrolysis)

The apparatus used for the extraction of aluminium by electrolysis is shown: a carbon anode (positive) dips into a solution of aluminium oxide in molten cryolite held in a cell…

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Question 26 · 1 mark · Air (composition)

Which gas is both an element and present in clean, dry air? A argon B carbon dioxide C chlorine D water vapour

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Question 27 · 1 mark · Air quality (catalytic converters)

Oxides of nitrogen formed in a car's engine are removed using a catalytic converter. What happens to the oxides of nitrogen in the catalytic converter? A They are hydrated. B They…

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Question 28 · 1 mark · Air and water (photosynthesis)

What is the equation for photosynthesis? A 6CO2 + 6H2O - C6H12O6 + 6O2 B 2CO2 + 2H2O - 2C2H5OH + 3O2 C C6H12O6 - 2CO2 + 2C2H5OH D C2H5OH + 3O2 - 2CO2 + 3H2O

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Question 29 · 1 mark · Organic chemistry (homologous series)

Four statements about members of the same homologous series are listed. 1 They have the same volatility. 2 They have the same molecular formula. 3 They have the same functional…

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Question 30 · 1 mark · Organic chemistry (saturation)

Ethene reacts with steam to produce ethanol. Which row describes each compound? ethene ethanol --- --- --- A saturated saturated B saturated unsaturated C unsaturated saturated D…

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Question 31 · 1 mark · Organic chemistry (cracking)

Which process is used to make an alkene from a long-chain alkane? A combustion B condensation C cracking D polymerisation

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Question 32 · 1 mark · Fuels (petroleum fractions)

Which fraction obtained from petroleum has the lowest boiling point? A diesel oil B fuel oil C kerosene D naphtha

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Question 33 · 1 mark · Organic chemistry (substitution reactions)

Alkanes undergo substitution reactions with chlorine in the presence of ultraviolet light. Which equation shows a reaction of this type? A C3H6 + Cl2 - C3H6Cl2 B C3H8 + Cl2 -…

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Question 34 · 1 mark · Organic chemistry (reactions of alkenes)

Information about two reactions of ethene is listed. - Reaction 1 requires a nickel catalyst. - Reaction 2 requires an acid catalyst. Which substance reacts with ethene in each…

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Question 35 · 1 mark · Organic chemistry (oxidation of ethanol)

Which process converts CH3CH2OH to CH3COOH? A bacterial oxidation B fermentation C catalytic addition of steam D catalytic addition of hydrogen

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Question 36 · 1 mark · Organic chemistry (esters)

The structure of an ester is shown: CH3CH2-C(=O)-O-CH2CH3. Which row identifies the name of the ester and the two compounds from which it is made? name compound 1 compound 2 ---…

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Question 37 · 1 mark · Polymers

Which statements about monomers or polymers are correct? 1 Monomers are always joined together by addition reactions. 2 A polymer can be formed from a single type of monomer. 3 A…

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Question 38 · 1 mark · Polymers (proteins)

The diagram shows the structure of a naturally occurring polymer, Q, with repeating -N-C(=O)- amide linkages. What is Q? A an amino acid B nylon C a protein D PET

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Question 39 · 1 mark · Purity (effect of impurities)

Which row shows how the boiling point and the melting point of water change when a soluble impurity is added to the water? boiling point melting point --- --- --- A increases…

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Question 40 · 1 mark · Identification of ions

X is a white powder. The following tests are done on X. - When a few drops of aqueous sodium hydroxide are added to a solution of X, no precipitate is seen. - When X is heated…

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