IGCSE Chemistry 0620 Paper 23, May/June 2026

Gaseous ammonia reacts with an excess of gaseous hydrogen chloride in a sealed flask. $${\text{NH}}_3\text{(g)}+\text{HCl(g)}\to {\text{NH}}_4\text{Cl(s)}$$ The reaction is exothermic. Which statements about the reaction are correct? 1 The number of gas particles in the flask decreases. 2 The average kinetic energy of the gas particles increases. 3 The activation energy of the reaction increases. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

X and Y are changes of state of water. $$\text{ice}\stackrel{\text{X}}{\to }\text{liquid water}\underset{\text{Y}}{\overset{}{\rightleftharpoons }}\text{water vapour}$$ Which row identifies X and Y?

A syringe contains a fixed mass of gas. The plunger of the syringe is free to move. Which row describes how the distance between the particles of the gas changes when the temperature or pressure is reduced?

Which substance is a pure compound? A air B brass C ethanol D petroleum

The diagram shows the structure of an atom of element J. What is element J? A boron B carbon C sodium D sulfur

Which statement about an atom or an ion is correct? A In an atom, the number of electrons is equal to the atomic number. B In an atom, the number of neutrons is equal to the atomic number. C In a sodium ion, ${\text{Na}}^{+}$, the number of electrons is greater than the atomic number. D An atom of hydrogen that contains one neutron has an atomic number of two.

Which statement explains the high melting point of potassium bromide? A There is strong covalent bonding between the molecules. B There is strong ionic bonding between the ions. C There are strong intermolecular forces between the molecules. D There are strong intermolecular forces between the ions.

Magnesium is in Group II and sulfur is in Group VI of the Periodic Table. They react to form magnesium sulfide. Which dot-and-cross diagram shows the outer electrons in magnesium sulfide? A [Diagram A] B [Diagram B] C [Diagram C] D [Diagram D]

Graphite is a form of carbon. Why can graphite be used as a lubricant? A Graphite contains unbonded electrons which move through the structure. B Graphite contains weak covalent bonds, so the atoms move easily. C Graphite has a low melting point, so it easily turns into a liquid. D Graphite has weak attractive forces between layers, so they can move.

The formula of an aluminium ion is ${\text{Al}}^{3+}$. The formula of a nitrate ion is ${\text{NO}}_3^{-}$. What is the formula of aluminium nitrate? A ${\text{AlNO}}_3$ B ${\text{Al(NO}}_3{)}_2$ C ${\text{Al}}_3{\text{NO}}_3$ D ${\text{Al(NO}}_3{)}_3$

Organic compound X has the following percentage composition by mass. $$\text{carbon }60\mathrm{\%};\text{ hydrogen }8\mathrm{\%};\text{ oxygen }32\mathrm{\%}$$ What is the empirical formula of compound X? A ${\text{C}}_5{\text{H}}_4\text{O}$ B ${\text{C}}_5{\text{H}}_8{\text{O}}_2$ C ${\text{C}}_{10}{\text{H}}_8{\text{O}}_4$ D ${\text{C}}_{15}{\text{H}}_2{\text{O}}_8$

The equation for the reaction of dilute sulfuric acid and aqueous sodium hydroxide is shown. $${\text{H}}_2{\text{SO}}_4+2\text{NaOH}\to {\text{Na}}_2{\text{SO}}_4+2{\text{H}}_2\text{O}$$ $25.0{\text{ cm}}^3$ of aqueous sodium hydroxide is measured into a conical flask. $12.5{\text{ cm}}^3$ of $0.100{\text{ mol / dm}}^3$ sulfuric acid is needed to completely react with the aqueous sodium hydroxide. What is the concentration of the aqueous sodium hydroxide? A $0.0250{\text{ mol / dm}}^3$ B $0.0500{\text{ mol / dm}}^3$ C $0.100{\text{ mol / dm}}^3$ D $0.200{\text{ mol / dm}}^3$

What is the total number of atoms in $0.0100\text{ mol}$ of methane, ${\text{CH}}_4$? (The value of the Avogadro constant is $6.02\times {10}^{23}$.) A $6.02\times {10}^{21}$ B $6.02\times {10}^{22}$ C $3.01\times {10}^{22}$ D $3.01\times {10}^{24}$

Dilute sulfuric acid is electrolysed using carbon electrodes. Which row shows the products that are formed at each electrode?

Substance Z is electrolysed with inert electrodes. The only product at the positive electrode is a gas which bleaches damp blue litmus paper. The only product at the negative electrode is a gas which gives a squeaky pop when it is tested with a lighted splint. What could substance Z be? 1 concentrated aqueous copper(II)chloride 2 concentrated aqueous sodium chloride 3 dilute aqueous potassium chloride A 1 and 3 B 1 only C 2 and 3 D 2 only

Aluminium is manufactured from aluminium oxide by electrolysis. Which row shows the ionic half-equations at each electrode and describes the role of cryolite in the process?

The equation for the reaction between hydrogen and chlorine is shown. $${\text{H}}_2\text{(g)}+{\text{Cl}}_2\text{(g)}\to 2\text{HCl(g)}$$ The energy required to break the H–H bond is $436\text{ kJ / mol}$. The energy required to break the Cl–Cl bond is $242\text{ kJ / mol}$. The energy released when making the H–Cl bond is $431\text{ kJ / mol}$. Which row shows the overall energy change in $\text{kJ / mol}$ and identifies the type of reaction?

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.

The equation for one of the reactions in the Contact process is shown. $$2{\text{SO}}_2\text{(g)}+{\text{O}}_2\text{(g)}\rightleftharpoons 2{\text{SO}}_3\text{(g)}\mathrm{\Delta }H=-196\text{ kJ / mol}$$ Which statement about this reaction is correct? A The typical conditions are a temperature of $450{}^{\circ }\text{C}$ and a pressure of $200\text{ atm}$. B The raw materials for this reaction are obtained from air and methane. C Iron is normally used as the catalyst to increase the rate of reaction. D Increasing the temperature increases the rate of reaction, but decreases the yield of ${\text{SO}}_3$.

Which row describes the effect of a catalyst on a reaction?

The ionic equation for the reaction of aqueous iron(II) sulfate with acidified aqueous potassium manganate(VII) is shown. $$5{\text{Fe}}^{2+}+{\text{MnO}}_4^{-}+8{\text{H}}^{+}\to 5{\text{Fe}}^{3+}+{\text{Mn}}^{2+}+4{\text{H}}_2\text{O}$$ Which statement about the reaction is correct? A The iron(II) ions gain electrons. B The iron(II) ions act as an oxidising agent. C The manganate(VII) ions are reduced. D The oxidation state of the iron(II) ions decreases.

Which statement about ethanoic acid is correct? A It is a weak acid that does not react with magnesium. B It is made by oxidising ethanol with aqueous sodium carbonate. C It reacts with an ester to form an alcohol. D It turns universal indicator orange.

Four oxides are listed. • calcium oxide • copper(II) oxide • sulfur dioxide • zinc oxide Which statement about these oxides is correct? A All of them contain oxide ions. B Only three of them are reduced by carbon to give a metal. C Only two of them react with aqueous NaOH to give a salt. D Only one of them will give a colour in the flame test.

Which salt is insoluble in water? A barium sulfate B lead(II) nitrate C magnesium chloride D sodium carbonate

The noble gases are in Group VIII of the Periodic Table. Some properties of the first four noble gases are shown.

Which row identifies the trends in boiling point and in density as Group VIII is descended?

The table shows some physical properties of four different substances. Which row describes the properties of a non-metallic element?

Which properties of aluminium make it useful in the manufacture of aircraft bodies? 1 It has good electrical conductivity. 2 It is resistant to corrosion. 3 It has a low density. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Four mixtures are listed. 1 ${\text{Cu}}^{2+}\text{(aq)}+\text{Ag(s)}$ 2 $\text{Zn(s)}+{\text{Fe}}^{2+}\text{(aq)}$ 3 ${\text{Cu}}^{2+}\text{(aq)}+\text{Mg(s)}$ 4 $\text{Cu(s)}+{\text{Ag}}^{+}\text{(aq)}$ Which mixtures would lead to a reaction? A 1, 2 and 3 B 1 and 3 only C 2, 3 and 4 D 2 and 4 only

A blue anhydrous substance is used to test for the presence of water. When water is added to this substance, it changes colour. What is the anhydrous substance and what is its colour after the addition of water?

Which gas is found in clean, dry air? A carbon monoxide B carbon dioxide C nitrogen dioxide D sulfur dioxide

Which statement describes how the C–H bonds in methane gas in the atmosphere contribute to global warming? A They absorb thermal energy from the Sun and emit some of this energy into space. B They absorb thermal energy from the Sun and emit all of this energy towards the Earth. C They absorb thermal energy from the Earth and emit all of this energy towards the Earth. D They absorb thermal energy from the Earth and emit some of this energy towards the Earth.

The formulas of three hydrocarbons are listed. 1 ${\text{CH}}_3{\text{CH(CH}}_3){\text{CH}}_3$ 2 ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{CHCH}}_2$ 3 ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2{\text{CH}}_3$ Which compounds are members of the same homologous series? A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Which row gives the correct structural and displayed formula of the named organic molecule?

Which equation describes an addition reaction? A ${\text{C}}_5{\text{H}}_{12}+8{\text{O}}_2\to 5{\text{CO}}_2+6{\text{H}}_2\text{O}$ B ${\text{C}}_3{\text{H}}_8+{\text{Br}}_2\to {\text{C}}_3{\text{H}}_7\text{Br}+\text{HBr}$ C ${\text{C}}_{10}{\text{H}}_{22}\to {\text{C}}_4{\text{H}}_8+{\text{C}}_6{\text{H}}_{12}+{\text{H}}_2$ D ${\text{C}}_4{\text{H}}_8+{\text{H}}_2\to {\text{C}}_4{\text{H}}_{10}$

Which reaction is used to make ethanol? A adding steam to ethene B addition polymerisation C fractional distillation of petroleum D reacting ethene with aqueous bromine

Which structure represents a protein? A [Structure A] B [Structure B] C [Structure C] D [Structure D]

Which structure represents the repeat unit of the addition polymer formed from but-1-ene? A [Structure A] B [Structure B] C [Structure C] D [Structure D]

A student measures the rate of two reactions. In one reaction, there is a change in mass of the reactants during the reaction. In the second reaction, there is a change in temperature during the reaction. Which piece of apparatus would be essential in both experiments? A balance B stop-watch C pipette D thermometer

The diagram shows a chromatography experiment. Which label shows the solvent front? A B C D solvent

Which row shows the reagents that are used to test for the chloride ion and for the sulfate ion?