IGCSE Chemistry 0620 Paper 22, Oct/Nov 2025

What happens to the volume of a fixed mass of gas when the temperature is increased or the pressure is decreased?

The diagram shows the heating curve for a substance. Between which two points do the particles of the substance change from being in fixed positions to being mobile? A P and Q B Q and R C S and T D T and U

A student investigates the diffusion of ammonia gas, ${\text{NH}}_3$, and hydrogen chloride gas, $\text{HCl}$. Two sets of apparatus are set up as shown at room temperature and pressure. The damp red litmus paper in apparatus 1 changes colour after 30 seconds. How long does it take for the damp blue litmus paper in apparatus 2 to change colour? A 21 seconds B 30 seconds C 64 seconds D The damp blue litmus paper does not change colour.

Which row describes elements, compounds and mixtures?

Which statement about atoms or ions is correct? A The mass number of an atom is the total number of nucleons and protons. B The electronic configuration of an aluminium ion, ${\text{Al}}^{3+}$, is 2,8,3. C Hydrogen is the only atom that has an incomplete first electron shell. D Most of the volume of an atom is taken up by its nucleus.

Which two values are used to calculate the relative atomic mass of a sample of boron?

Which statement describes the structure of sodium chloride? A a lattice of alternating positive and negative ions B a lattice of positive ions surrounded by a 'sea' of delocalised electrons C a mixture of sodium and chlorine atoms D a regular lattice of sodium and chlorine atoms

Graphite and diamond are both forms of the element carbon. Which row shows the number of other carbon atoms that each carbon atom is covalently bonded to in graphite and in diamond?

Which row describes the structure and bonding in cobalt?

The equation for the combustion of ethanol is shown. $${\text{C}}_2{\text{H}}_5\text{OH}+3{\text{O}}_2\to 2{\text{CO}}_2+3{\text{H}}_2\text{O}$$ The relative molecular mass, $M_r$, of ethanol is 46. Which statement about the reaction is correct? A 4.6 g of ethanol produces 4.4 g of carbon dioxide. B 92 g of ethanol produces 88 g of carbon dioxide and 108 g of water. C 138 g of ethanol reacts with 32 g of oxygen. D 184 g of ethanol produces 216 g of water.

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen only. The relative molecular mass, $M_r$, of the compound is 60. Which row shows the empirical formula and the molecular formula of the compound?

Hydrogen–oxygen fuel cells are used in electric cars. Three statements about these fuel cells are listed. 1 The process in the cell is called electrolysis. 2 Water is broken down in the cell to produce hydrogen, oxygen and electricity. 3 Water is the only chemical product formed in the reaction. Which statements are correct? A 1 and 2 B 1 and 3 C 2 only D 3 only

A solution of copper(II) sulfate can be electrolysed using copper electrodes or carbon electrodes. Which statements are correct? 1 Using copper electrodes, oxygen gas forms at the anode. 2 Using copper electrodes, copper atoms lose electrons at the anode. 3 Using carbon electrodes, copper metal forms at the cathode. 4 Using carbon electrodes, copper ions gain electrons at the cathode. A 1 and 2 B 1 and 3 C 2, 3 and 4 D 4 only

The equation for the combustion of hydrazine, ${\text{N}}_2{\text{H}}_4$, is shown.

What is the overall enthalpy change for the combustion of one mole of hydrazine? A –327 kJ / mol B –111 kJ / mol C +111 kJ / mol D +327 kJ / mol

Dissolving ammonium chloride in water is an endothermic change. Which row shows the energy change and temperature change of the mixture during the dissolving of ammonium chloride?

Aqueous sodium thiosulfate, ${\text{Na}}_2{\text{S}}_2{\text{O}}_3$, reacts with dilute hydrochloric acid to form a yellow precipitate of sulfur. $${\text{Na}}_2{\text{S}}_2{\text{O}}_3\text{(aq)}+2\text{HCl(aq)}\to 2\text{NaCl(aq)}+{\text{H}}_2\text{O(l)}+\text{S(s)}+{\text{SO}}_2\text{(g)}$$ The precipitate forms more quickly when the reactants are heated. Which statements explain this observation? 1 The reacting particles collide more frequently. 2 The collisions between reacting particles have more energy. 3 The activation energy of the reaction is lower. A 1 and 2 B 1 and 3 C 1 only D 2 and 3

Which statement about the conditions used in the Haber process and in the Contact process is correct? A The typical pressure used in the Haber process is similar to that used in the Contact process. B The typical temperature used in the Haber process is similar to that used in the Contact process. C The Haber process uses a vanadium(V) oxide catalyst, and the Contact process uses an iron catalyst. D Both processes produce an acidic gas.

The equation shows the equilibrium between dinitrogen tetroxide, ${\text{N}}_2{\text{O}}_4$, and nitrogen dioxide, ${\text{NO}}_2$. The colours of the reactant and product are shown. $$\mathrm{<munder><mo><msub><mtext>N</mtext><mn>2</mn></msub><msub><mtext>O</mtext><mn>4</mn></msub><mtext>(g)</mtext></mo><mtext>colourless</mtext></munder>}\rightleftharpoons \mathrm{<munder><mo><mn>2</mn><msub><mtext>NO</mtext><mn>2</mn></msub><mtext>(g)</mtext></mo><mtext>brown</mtext></munder>}$$ The forward reaction is endothermic. Which statement is not correct? A At equilibrium, the concentrations of the reactant and the product stay constant. B At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction. C When the pressure is increased, a darker brown colour is seen. D When the temperature is increased, a darker brown colour is seen.

What is the oxidation number of chromium in the ${\text{Cr}}_2{\text{O}}_7^{2-}$ ion? A –2 B –1 C +6 D +12

Which method is used to prepare a pure, dry sample of lead(II) chloride? A mix aqueous lead(II) nitrate and dilute hydrochloric acid $\to$ filter $\to$ crystallise and dry the filtrate B mix aqueous lead(II) nitrate and dilute hydrochloric acid $\to$ filter $\to$ wash and dry the residue C mix solid lead(II) hydroxide and aqueous sodium chloride $\to$ filter $\to$ crystallise and dry the filtrate D mix solid lead(II) hydroxide and aqueous sodium chloride $\to$ filter $\to$ wash and dry the residue

Phosphorus is an element in Group V of the Periodic Table. It burns in air to form an oxide that dissolves in water to form a solution with a pH of 1. Which row describes this oxide of phosphorus?

The equation shows the reaction between aqueous hydrogen bromide and aqueous ammonia. $$\text{HBr(aq)}+{\text{NH}}_3\text{(aq)}\to {\text{NH}}_4^{+}\text{(aq)}+{\text{Br}}^{-}\text{(aq)}$$ Which statement describes the role of aqueous hydrogen bromide? A It is a catalyst. B It is a reducing agent. C It is a proton acceptor. D It is a proton donor.

Which statement about the elements in Group I is correct? A Hydrogen is produced when Group I elements react with water. B Ions of Group I elements have a 1– charge. C Sodium is more reactive than potassium. D Solid sodium is a poor electrical conductor.

Which row describes the colour and state of iodine at room temperature and pressure?

Part of the Periodic Table is shown. Which element is an inert gas?

Four different metals are separately added to water. The oxide of each metal is separately heated with carbon. The results are shown.

What is the order of reactivity of the four metals, least reactive first? A Q $\to$ T $\to$ S $\to$ R B Q $\to$ S $\to$ T $\to$ R C R $\to$ S $\to$ T $\to$ Q D R $\to$ T $\to$ S $\to$ Q

An iron nail is fully covered with zinc to prevent it from rusting. Which row describes this method of protection and explains why zinc is used to protect the iron nail?

Iron is extracted from hematite in the blast furnace. Which reaction increases the temperature in the blast furnace to over 1500 °C? A calcium carbonate $\to$ calcium oxide + carbon dioxide B calcium oxide + silicon(IV) oxide $\to$ calcium silicate C carbon + oxygen $\to$ carbon dioxide D carbon dioxide + carbon $\to$ carbon monoxide

Aluminium is extracted by the electrolysis of purified bauxite. Which row shows the half-equations at the electrodes and explains why one of the electrodes has to be replaced regularly?

Which flow chart describes the correct treatment sequence of the domestic water supply? A filtration $\to$ chlorination $\to$ sedimentation B sedimentation $\to$ chlorination $\to$ filtration C chlorination $\to$ filtration $\to$ sedimentation D sedimentation $\to$ filtration $\to$ chlorination

Which statement about oxides of nitrogen is correct? A They are made in car engines by the incomplete combustion of gasoline at a high temperature. B They are made in car engines when nitrogen in gasoline reacts with oxygen in air at a high temperature. C They are removed from car exhausts by catalytic converters and form nitrogen and sulfur dioxide. D They are removed from car exhausts when they react with carbon monoxide in catalytic converters.

The alkenes are a homologous series. Which statement about the members of the homologous series of the alkenes is correct? A They have the same functional group. B They have the same relative molecular mass. C They have different chemical properties. D They have different general formulae.

The diagram represents two processes, X and Y, and their effect, Z, in increasing global warming. Which row identifies X, Y and Z?

Which structures are structural isomers of each other? A 1, 2, 3 and 4 B 1, 2 and 4 only C 1 and 3 only D 2 and 4 only

The structure of an ester is shown. What is the name of this ester? A ethyl methanoate B methyl ethanoate C propyl methanoate D methyl propanoate

Which row shows the products obtained by the cracking of a large alkane?

Ethanol is produced by the fermentation of aqueous glucose or by the catalytic addition of steam to ethene. Which row shows some advantages and disadvantages of these processes?

Propenoic acid is an organic compound that is both an alkene and a carboxylic acid. The structure of propenoic acid is shown. Which structure represents one repeat unit of the addition polymer formed from propenoic acid?

Which item of apparatus is used to measure $13.7{\text{ cm}}^3$ of dilute hydrochloric acid? A a balance B a burette C a conical flask D a volumetric pipette

Chromatography is used to separate and analyse mixtures of soluble substances. The first steps of the process are listed. ● apply sample to baseline ● develop chromatogram in solvent What is the next step in the process to detect soluble colourless substances? A calculate the $R_{\text{f}}$ values B compare the results with known substances C count the number of spots D use a suitable locating agent