IGCSE Chemistry 0620/23 Past Paper, May/June 2023

1

Nitrogen is heated in a balloon, which expands slightly. Which statements about the molecules of nitrogen are correct? 1 They move further apart. 2 They move more quickly. 3 They remain the same distance apart. 4 Their speed remains unchanged. A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4

2

The diagrams represent some elements, compounds and mixtures. Which row describes the numbered substances?

	$1$	$2$	$3$	$4$
$A$	element	mixture of compounds	compound	mixture of elements
$B$	compound	mixture of compounds	element	mixture of elements
$C$	element	mixture of elements	compound	mixture of compounds
$D$	compound	mixture of elements	element	mixture of compounds

3

Two atoms, X and Y, have the same mass number but different atomic numbers. Which statement about X and Y is correct? A They have the same number of protons. B They have the same number of electrons. C They are in the same group of the Periodic Table. D They have different numbers of neutrons.

4

A sample of pure iron contains three isotopes only.

$percentageabundanceof isotope / %$	isotope
$2$	$^{n} Fe$
$6$	$^{54} Fe$
$92$	$^{56} Fe$

The iron in the sample has a relative atomic mass of 55.9. What is the value of $n$ ? A 53 B 55 C 57 D 58

5

Magnesium oxide is a white solid at room temperature and pressure. Part of the structure of solid magnesium oxide is shown. key $∙ = {Mg}^{2 +} magnesium ion$ $◯ = O^{2 -} oxide ion$ Three statements are listed. 1 Magnesium ions are smaller than oxide ions because they contain fewer electrons. 2 Magnesium oxide has good electrical conductivity when molten because the ions are mobile. 3 Magnesium oxide has a high melting point because of the strong electrostatic attraction between the ions and delocalised electrons in the giant lattice. Which statements are correct? A 1 and 2 B 1 and 3 C 2 and 3 D 2 only

6

In which molecule are all the outer-shell electrons involved in covalent bonding? A ${Cl}_{2}$ B ${CH}_{4}$ C $HCl$ D ${NH}_{3}$

7

Which row describes the properties of silicon(IV) oxide?

	$giant covalentstructure$	melting point
$A$	no	high
$B$	no	low
$C$	yes	high
$D$	yes	low

8

Which row describes the structure of a solid metal and explains the property?

	structure of solid metal	property of solid metal
$A$	$lattice of negative ionsin a sea of electrons$	$conducts electricity becausethe electrons are free to move$
$B$	$lattice of negative ionsin a sea of electrons$	$is malleable because the layersof ions can slide over each other$
$C$	$lattice of positive ionsin a sea of electrons$	$conducts electricity becausethe ions are free to move$
$D$	$lattice of positive ionsin a sea of electrons$	$is malleable because the layersof ions can slide over each other$

9

What is the formula of potassium oxide? A $P_{2} O$ B ${PO}_{2}$ C $KO$ D $K_{2} O$

10

A dilute aqueous solution of sodium bromide is electrolysed using inert electrodes. Which row identifies the product at the cathode and at the anode?

	cathode	anode
$A$	bromine	hydrogen
$B$	hydrogen	bromine
$C$	hydrogen	oxygen
$D$	oxygen	hydrogen

11

Aluminium is extracted by electrolysis, as shown. Which row shows the ionic half-equations at the cathode and the anode?

	cathode	anode
$A$	${Al}^{3 +} \to Al + 3 e^{-}$	$2 O^{2 -} \to O_{2} + 4 e^{-}$
$B$	${Al}^{3 +} \to Al + 3 e^{-}$	$2 O^{2 -} + 4 e^{-} \to O_{2}$
$C$	${Al}^{3 +} + 3 e^{-} \to Al$	$2 O^{2 -} \to O_{2} + 4 e^{-}$
$D$	${Al}^{3 +} + 3 e^{-} \to Al$	$2 O^{2 -} + 4 e^{-} \to O_{2}$

12

The reaction pathway diagram for an exothermic reaction is shown. Which row identifies labels 1, 2, 3 and 4?

	$1$	$2$	$3$	$4$
$A$	reactants	$Δ H$	$E_{a}$	products
$B$	products	$Δ H$	$E_{a}$	reactants
$C$	reactants	$E_{a}$	$Δ H$	products
$D$	products	$E_{a}$	$Δ H$	reactants

13

The equation for the complete combustion of ethene is shown. $C_{2} H_{4} (g) + 3 O_{2} (g) \to 2 {CO}_{2} (g) + 2 H_{2} O (g)$ Some bond energies are listed.

bond	$bond energyin kJ/mol$
C–H	$412$
C–C	$348$
C=C	$612$
C–O	$360$
C=O	$743$
O–O	$146$
O=O	$496$
O–H	$463$

What is the overall energy change when one mole of ethene is completely burned? A $- 456$ B $- 1076$ C $- 1340$ D $- 2126$

14

Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen. Why does magnesium powder react faster than magnesium ribbon? A The magnesium atoms in the powder have a lower activation energy. B The powder has a smaller surface area. C The magnesium atoms in the powder have more frequent collisions with acid particles. D The magnesium atoms in the powder have greater kinetic energy.

15

Which row shows the conditions used in the Contact process?

	catalyst	$pressure / atm$	$temperature /^{\circ} C$
$A$	iron	$2$	$100$
$B$	iron	$200$	$450$
$C$	vanadium(V) oxide	$2$	$450$
$D$	vanadium(V) oxide	$200$	$100$

16

A student heats hydrated copper(II) sulfate. The blue crystals change to a white powder. How can the student reverse this reaction? A Add anhydrous copper(II) sulfate to the white powder. B Add water to the white powder. C Cool the white powder. D Reheat the white powder.

17

Which reaction of hydrochloric acid is a redox reaction? A ${MgCO}_{3} + 2 HCl \to {MgCl}_{2} + H_{2} O + {CO}_{2}$ B ${Mg(OH)}_{2} + 2 HCl \to {MgCl}_{2} + 2 H_{2} O$ C $MgO + 2 HCl \to {MgCl}_{2} + H_{2} O$ D $Mg + 2 HCl \to {MgCl}_{2} + H_{2}$

18

Which oxide is amphoteric? A ${Al}_{2} O_{3}$ B $CaO$ C ${Na}_{2} O$ D ${SO}_{2}$

19

Four statements about strong acids are listed. 1 They react with carbonates to form carbon dioxide. 2 They completely dissociate in aqueous solution. 3 They react with ammonium salts to form ammonia. 4 They are proton acceptors. Which statements are correct? A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

20

Which reaction mixture will produce a precipitate? A aqueous ${Na}_{2} {CO}_{3}$ and aqueous ${CuSO}_{4}$ B dilute $H_{2} {SO}_{4}$ and aqueous $NaOH$ C dilute ${HNO}_{3}$ and solid $MgO$ D solid $CuO$ and dilute $H_{2} {SO}_{4}$

21

Which set of elements shows the change from metallic to non-metallic character across a period of the Periodic Table? A beryllium $\to$ magnesium $\to$ calcium B fluorine $\to$ bromine $\to$ iodine C oxygen $\to$ boron $\to$ lithium D sodium $\to$ silicon $\to$ chlorine

22

A sample of ethanoic acid and a sample of hydrochloric acid have the same concentration. How do the hydrogen ion concentration and pH of ethanoic acid compare to those of hydrochloric acid?

	$ethanoic acid comparedto hydrochloric acid$
	$hydrogen ionconcentration$	pH
$A$	higher	higher
$B$	higher	lower
$C$	lower	higher
$D$	lower	lower

23

What is a typical property of transition elements? A can act as catalysts B poor electrical conductivity C low melting point D low density

24

Which statement about copper or aluminium is correct? A Aluminium is more dense than copper. B Aluminium is less reactive than copper. C Copper has high ductility. D Copper has poor electrical conductivity.

25

Water from a reservoir flows to the water works where purification process 1 takes place followed by process 2. What are processes 1 and 2?

	process 1	process 2
$A$	chlorination	filtration
$B$	filtration	chlorination
$C$	fractional distillation	filtration
$D$	filtration	fractional distillation

26

Calcium reacts with cold water to produce hydrogen. Lead reacts slowly when heated in air to form an oxide but has almost no reaction with steam. Silver does not react with either air or water. Zinc reacts when heated with steam to produce hydrogen. What is the order of reactivity starting with the least reactive?

	least reactive			$⟶$	most reactive
$A$	calcium	lead	zinc		silver
$B$	calcium	zinc	lead		silver
$C$	silver	lead	zinc		calcium
$D$	silver	zinc	lead		calcium

27

Blocks of magnesium are attached to the bottom of a steel boat to prevent rusting. Which equation describes a change that prevents the steel from rusting? A $Fe \to {Fe}^{3 +} + 3 e^{-}$ B ${Fe}_{2} O_{3} + 3 Mg \to 2 Fe + 3 MgO$ C $3 {Mg}^{2 +} + 2 Fe \to 2 {Fe}^{3 +} + 3 Mg$ D $Mg \to {Mg}^{2 +} + 2 e^{-}$

28

Which statements about the extraction of iron in a blast furnace are correct? 1 The temperature inside the blast furnace is increased by burning carbon. 2 Iron(III) oxide is reduced to iron by carbon monoxide. 3 The thermal decomposition of calcium carbonate forms slag. 4 Slag reacts with acidic impurities. A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4

29

Which statements about water are correct? 1 Tap water has fewer impurities than distilled water. 2 Tap water will turn anhydrous cobalt(II) chloride pink. 3 The domestic water supply is treated with carbon to kill microbes. 4 Phosphates from fertilisers can cause deoxygenation of water. A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

30

Oxides of nitrogen form in car engines and are removed by catalytic converters. Which equation represents a reaction that occurs in a catalytic converter? A $CO + {NO}_{2} \to NO + {CO}_{2}$ B $2 CO + 2 NO \to N_{2} + 2 {CO}_{2}$ C ${CO}_{2} + NO \to {NO}_{2} + CO$ D ${CO}_{2} + 2 {NO}_{2} \to N_{2} + 3 O_{2} + C$

31

An alkene is represented by the formula ${CH}_{3} {CH=CH}_{2}$ . Which name is given to this type of formula? A displayed B empirical C general D structural

32

What is the structure of propanoic acid? A

H	H	O
$∣$	$∣$	$/ /$
$H - C - C - C$
$∣$	$∣$	$\$
H	H	OH

B

H	H	H	O
$∣$	$∣$	$∣$	$/ /$
$H - C - C - C - C$
$∣$	$∣$	$∣$	$\$
H	H	H	OH

C

H	H	H
$∣$	$∣$	$∣$
$H - C - C - C - OH$
$∣$	$∣$	$∣$
H	H	H

D

H	H	H	H
$∣$	$∣$	$∣$	$∣$
$H - C - C - C - C - OH$
$∣$	$∣$	$∣$	$∣$
H	H	H	H

33

Butane reacts with chlorine in the presence of ultraviolet radiation. What is the equation for this reaction? A $C_{4} H_{10} + {Cl}_{2} \to C_{4} H_{8} {Cl}_{2} + H_{2}$ B $C_{4} H_{10} + {Cl}_{2} \to C_{4} H_{9} Cl + HCl$ C $C_{4} H_{10} + {Cl}_{2} \to 2 C_{2} H_{5} Cl + H_{2}$ D $C_{4} H_{10} + {Cl}_{2} \to C_{2} H_{4} + C_{2} H_{5} Cl + HCl$

34

A hydrocarbon P is cracked to make compound Q and hydrogen. Compound R is formed by the addition polymerisation of compound Q. To which homologous series do P, Q and R belong?

	alkene	alkane
$A$	P only	Q and R
$B$	Q only	P and R
$C$	P and Q	R only
$D$	P and R	Q only

35

Which substances are structural isomers? A but-2-ene and propene B ethyl ethanoate and butanoic acid C methyl methanoate and ethanol D propan-1-ol and butan-1-ol

36

Ethanol is produced by: 1 the catalytic addition of steam to ethene 2 fermentation. Which statement is correct? A Both processes use similar amounts of energy. B Both processes use a catalyst. C Process 1 uses a temperature of 25–35 °C. D Process 2 uses a pressure of 60 atm.

37

The two monomers shown can be used to form a condensation polymer.

O

H

O / /

∣

∣

∣

∣

/ / C -

C -

C -

C -

C -

C /

∣

∣

∣

∣

\ H - O

H

O - H

H

H ∣

∣

∣

∣

∣

∣

∣

∣ N -

C -

C -

C -

C -

C -

C -

N /

∣

∣

∣

∣

∣

∣

\ H

H

Which small molecule is released during this reaction? A $H_{2} O$ B ${NH}_{3}$ C ${CO}_{2}$ D ${CONH}_{2}$

38

Dilute hydrochloric acid is titrated into a conical flask containing sodium hydroxide solution and a few drops of methyl orange indicator. Which piece of apparatus is used to add the hydrochloric acid? A beaker B burette C measuring cylinder D pipette

39

The chromatogram obtained from a chromatography experiment on substance S is shown. What is the $R_{f}$ value of S? A 0.39 B 0.46 C 0.56 D 0.62

40

Element X burns in air to form an acidic gas that decolourises potassium manganate(VII). What is X? A carbon B nitrogen C magnesium D sulfur

IGCSE Chemistry 0620 Paper 23, May/June 2023

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