IGCSE Chemistry 0620 Paper 21, Oct/Nov 2025

A sealed balloon contains air. The temperature of the balloon is increased. Which row describes how the pressure in the balloon and the kinetic energy of the particles in air change?

Ammonia gas is reacted with hydrogen chloride gas using the apparatus shown. Solid ammonium chloride is produced. Which statement explains why the solid ammonium chloride is formed nearer to the hydrogen chloride? A Aqueous ammonia is a base and aqueous hydrogen chloride is an acid. B Ammonia molecules diffuse more slowly than hydrogen chloride molecules. C Hydrogen chloride has a greater molecular mass than ammonia. D Only ammonia molecules diffuse in all directions at the same time.

The table shows information about four different particles.

What are the values of W, X, Y and Z?

Substances with giant covalent structures can be used as lubricants and as cutting tools for hard materials. The diagrams show how the atoms are arranged in two giant covalent substances, P and Q. Which statement is correct? A Only P is used as a cutting tool and only Q is used as a lubricant. B Only P is used as a lubricant and only Q is used as a cutting tool. C P and Q are both used as cutting tools. D P and Q are both used as lubricants.

Symbols representing four particles are shown. $${}_{20}^{40}\text{W}{}_{20}^{41}{\text{X}}^{2+}{}_{18}^{37}\text{Y}{}_{17}^{37}\text{Z}$$ The letters are not the chemical symbols. Which particles have the same number of neutrons? A W and ${\text{X}}^{2+}$ B W and Z C ${\text{X}}^{2+}$ and Y D Y and Z

Which statement describes the formation of bonds in lithium bromide? A A lithium atom donates one electron to a bromine atom. B A bromine atom donates one electron to a lithium atom. C A lithium atom shares a pair of electrons with a bromine atom. D A bromine atom donates a pair of electrons to a lithium atom.

Which statement explains why solid magnesium is a good conductor of electricity? A Magnesium has delocalised electrons that can move through the lattice. B Magnesium has strong attractions between ions. C Magnesium consists of a giant lattice of anions in a ‘sea’ of delocalised electrons. D Magnesium consists of metal ions that move through the lattice.

The equation for the reaction between dilute ethanoic acid and aqueous lithium hydroxide is shown. $$\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}+\mathrm{L}\mathrm{i}\mathrm{O}\mathrm{H}\to \mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{L}\mathrm{i}+{\mathrm{H}}_2\mathrm{O}$$ In an experiment, $20.0{\mathrm{c}\mathrm{m}}^3$ of $0.050{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ aqueous lithium hydroxide is exactly neutralised by $12.5{\mathrm{c}\mathrm{m}}^3$ of dilute ethanoic acid. Which statement is correct? A The amount of lithium hydroxide is equal to $0.050\times \frac{1000}{20}\mathrm{m}\mathrm{o}\mathrm{l}$. B The amount of ethanoic acid reacted is $0.0010\mathrm{m}\mathrm{o}\mathrm{l}$. C The concentration of the dilute ethanoic acid is $0.16{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$. D The volume of aqueous lithium hydroxide used is $0.20{\mathrm{d}\mathrm{m}}^3$.

The molecular formulae of four compounds are listed. 1 $\mathrm{C}{\mathrm{H}}_4$ 2 ${\mathrm{C}}_2{\mathrm{H}}_6$ 3 ${\mathrm{C}}_3{\mathrm{H}}_8$ 4 ${\mathrm{C}}_3{\mathrm{H}}_6$ Which molecular formulae are also the empirical formulae for the compounds? A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

The equation for the reaction between copper(II) oxide, $\mathrm{C}\mathrm{u}\mathrm{O}$, and ammonia is given. $$3\mathrm{C}\mathrm{u}\mathrm{O}+2\mathrm{N}{\mathrm{H}}_3\to 3\mathrm{C}\mathrm{u}+3{\mathrm{H}}_2\mathrm{O}+{\mathrm{N}}_2$$ [$M_r$: $\mathrm{C}\mathrm{u}\mathrm{O}$, 80; $\mathrm{N}{\mathrm{H}}_3$, 17; ${\mathrm{H}}_2\mathrm{O}$, 18; ${\mathrm{N}}_2$, 28] [$A_r$: $\mathrm{C}\mathrm{u}$, 64] Which statements about this reaction are correct? 1 $80.0\mathrm{g}$ of copper(II) oxide reacts exactly with $17.0\mathrm{g}$ of ammonia. 2 $4.0\mathrm{g}$ of copper(II) oxide reacts with excess ammonia to produce $3.2\mathrm{g}$ of copper. 3 The mass of water produced in this reaction is greater than the mass of nitrogen. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

How many atoms are present in $1.00\mathrm{m}\mathrm{o}\mathrm{l}$ of argon? A $2.06\times {10}^{23}$ B $3.02\times {10}^{26}$ C $6.02\times {10}^{23}$ D $6.32\times {10}^{20}$

Aqueous copper(II) sulfate is electrolysed using copper electrodes. Which statement is correct? A Oxygen gas is produced at the positive electrode. B The blue colour of the solution gradually fades. C The concentration of copper ions in the solution stays the same. D The mass of the negative electrode decreases.

Which row describes the reactions during the electrolysis of dilute aqueous sodium chloride?

Information about two reactions is given. ● The neutralisation reaction between citric acid and sodium hydrogencarbonate is endothermic. ● The displacement reaction between magnesium and carbon dioxide is exothermic. Which statements about the two reactions are correct? 1 The energy of the products formed in the neutralisation reaction is greater than the energy of the reactants. 2 The energy of magnesium and carbon dioxide is greater than the energy of magnesium oxide and carbon. 3 In an exothermic reaction, the energy required to break the bonds is greater than the energy released when the new bonds are formed. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

The reaction pathway diagram for a reaction is shown. Which row identifies the activation energy, $E_{\mathrm{a}}$, and the enthalpy change, $\mathrm{\Delta }H$, for this reaction?

Hydrogen peroxide solution decomposes very slowly at room temperature to produce oxygen gas. This gas forms a rising foam when liquid detergent is added. Five test-tubes are half-filled with hydrogen peroxide solution. A drop of liquid detergent is added to each one. Different metal oxides are added to four of the test-tubes and the height of the foam formed after one minute is measured. The results are shown.

Which conclusion can be drawn from these results? A Metal oxides do not affect the rate of this reaction. B All metal oxides increase the rate of this reaction and act as catalysts. C Manganese(IV) oxide is the best catalyst of the four metal oxides tested. D Only transition element oxides increase the rate of this reaction.

Which equation represents one of the reactions in the Contact process? A $2\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{S}{\mathrm{O}}_3(\mathrm{g})$ B $2\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{S}{\mathrm{O}}_3(\mathrm{a}\mathrm{q})$ C $2\mathrm{S}{\mathrm{O}}_3(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{S}{\mathrm{O}}_4(\mathrm{a}\mathrm{q})$ D $2\mathrm{S}{\mathrm{O}}_3(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{S}{\mathrm{O}}_4(\mathrm{g})$

The ionic equation for the redox reaction between acidified manganate(VII) ions and iodide ions is shown. $$2\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}(\mathrm{a}\mathrm{q})+16{\mathrm{H}}^{+}(\mathrm{a}\mathrm{q})+10{\mathrm{I}}^{-}(\mathrm{a}\mathrm{q})\to 2\mathrm{M}{\mathrm{n}}^{2+}(\mathrm{a}\mathrm{q})+5{\mathrm{I}}_2(\mathrm{a}\mathrm{q})+8{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$$ Which row shows the changes in oxidation number for manganese and for iodine during this reaction?

In the Haber process, nitrogen and hydrogen react to form ammonia. $${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2\mathrm{N}{\mathrm{H}}_3$$ The forward reaction is exothermic. Which changes in pressure and temperature increase the yield of ammonia?

Which statement describes a property of ethanoic acid? A It does not produce carbon dioxide when added to sodium carbonate. B It does not produce hydrogen when added to magnesium. C It only donates some of its protons when added to excess aqueous sodium hydroxide. D It only partially dissociates when added to water.

A student adds different solid salts to an excess of water. The student stirs the mixtures to determine the solubilities of the salts. The results are shown. What could the four different salts be?

Four metal oxides are listed. 1 $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ 2 $\mathrm{C}\mathrm{a}\mathrm{O}$ 3 $\mathrm{C}\mathrm{u}\mathrm{O}$ 4 $\mathrm{Z}\mathrm{n}\mathrm{O}$ Which metal oxides are amphoteric? A 1 and 4 B 1 only C 2, 3 and 4 D 2 and 3 only

The ions formed when element X and element Y react together are shown. ● Element X forms ${\text{X}}^{-}$ ions. ● Element Y forms ${\text{Y}}^{2+}$ ions. Which row identifies the position of X and of Y in the Periodic Table?

Which properties decrease down the group of alkali metals? 1 melting point 2 density 3 reactivity A 1 and 2 B 1 only C 2 and 3 D 3 only

Some halide ions are displaced from aqueous potassium halides by halogens. In which mixtures are the halide ions displaced? 1 potassium bromide and chlorine 2 potassium bromide and iodine 3 potassium iodide and chlorine 4 potassium chloride and iodine A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

What is the correct order of reactivity of the following metals, from least reactive to most reactive? A calcium $\to$ magnesium $\to$ zinc $\to$ copper B copper $\to$ zinc $\to$ magnesium $\to$ calcium C copper $\to$ zinc $\to$ calcium $\to$ magnesium D zinc $\to$ copper $\to$ magnesium $\to$ calcium

The equation for the reaction between aluminium and iron(III) oxide is shown. $$2\mathrm{A}\mathrm{l}+\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3\to \mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3+2\mathrm{F}\mathrm{e}$$ Which statement about this reaction is correct? A The aluminium acts as an oxidising agent. B It shows that iron is more reactive than aluminium. C The oxidation number of the aluminium decreases during the reaction. D It shows that aluminium has a greater tendency to form ions than iron.

Which row identifies methods used to prevent iron from rusting?

key ✓ = yes ✗ = no

Which statement about the extraction of aluminium by electrolysis is correct? A Aluminium oxide is dissolved in molten cryolite to increase its melting point. B At the cathode, oxygen ions lose electrons to form oxygen gas. C The carbon in the graphite anode reacts with oxygen gas forming carbon dioxide. D The reaction at the anode is $\mathrm{A}{\mathrm{l}}^{3+}+3{\mathrm{e}}^{-}\to \mathrm{A}\mathrm{l}$.

Catalytic converters are used to remove oxides of nitrogen from exhaust gases. The equation represents one of the reactions that occur in a catalytic converter. $$2\mathrm{N}\mathrm{O}+2\mathrm{C}\mathrm{O}\to {\mathrm{N}}_2+2\mathrm{C}{\mathrm{O}}_2$$ What is a disadvantage of using a catalytic converter to remove oxides of nitrogen? A CO is an essential reactant in photosynthesis. B $\mathrm{C}{\mathrm{O}}_2$ is a greenhouse gas. C ${\mathrm{N}}_2$ is acidic. D ${\mathrm{N}}_2$ is toxic.

Some gases are present in clean, dry air, while other gases are only present in polluted air. Which row is correct?

Petroleum is separated by fractional distillation. Which statement about the fractions produced is correct? A Bottled gas for heating and cooking is obtained from the naphtha fraction. B Diesel oil is used as a fuel for jet aircraft. C Substances used to make polishes are obtained from the lubricating fraction. D The kerosene fraction contains many useful waxes.

Which structure represents a compound in the alcohol homologous series? A

B

C

D

Ethane reacts with chlorine. Which row identifies the type of reaction and the formulae of the products formed?

Which equation represents the formation of poly(propene) from propene?

Ethene reacts with hydrogen in an addition reaction to form ethane. Which catalyst is used for this reaction? A iron B nickel C vanadium(V) oxide D yeast

What is produced by the bacterial oxidation of ethanol? A ethene B sodium ethanoate C ethyl ethanoate D vinegar

Which statement about addition polymers or condensation polymers is correct? A Addition polymers only contain carbon and hydrogen atoms. B One of the monomers used to make a polyester is a diamine. C Addition polymers contain carbon–carbon double bonds in the main chain. D Water is an additional product in the formation of a protein from amino acids.

The results of flame tests on three metal salts, X, Y and Z, are shown.

Which row identifies the cations present in X, Y and Z?

Ethanol can be made by fermentation of sugar, using yeast. This produces a mixture of ethanol and water. How is ethanol separated from this mixture? A distilling the mixture using a fractionating column B filtering the mixture C heating to evaporate most of the water, and allowing the ethanol to crystallise D heating to evaporate the water