O Level Chemistry 5070 Paper 12, Oct/Nov 2025

Separate samples of water and air each have a volume of $30{\text{ cm}}^3$ at room temperature and pressure. The pressure applied to both samples is increased by the same amount at room temperature. Which row describes the volumes at the increased pressure?

Why does a balloon full of helium gas become smaller as the temperature changes from $30{}^{\circ }\text{C}$ to $10{}^{\circ }\text{C}$? A The gas condenses to a liquid and so takes up less space. B The gas particles become smaller at lower temperatures. C The gas particles diffuse through the balloon and escape. D The gas particles move more slowly so reducing the pressure.

Atom X has an atomic number of 19 and a nucleon number of 42. Atom Y has an atomic number of 20 and a nucleon number of 40. Which statement is correct? A Atom X contains two more electrons than atom Y. B Atom X contains three more neutrons than atom Y. C Atom Y contains one more neutron than atom X. D X and Y are atoms of the same element.

In which ionic compound do all the ions have the same electronic configuration? A beryllium sulfide B lithium fluoride C magnesium chloride D sodium oxide

Which ion has a positive charge? A ammonium B carbonate C manganate(VII) D sulfite

Which row is correct?

Powdered calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide. What is the correct ionic equation, including state symbols, for this reaction? A ${\text{CaCO}}_3\text{(s)}+2\text{HCl(aq)}\to {\text{CaCl}}_2\text{(aq)}+{\text{H}}_2\text{O(l)}+{\text{CO}}_2\text{(g)}$ B ${\text{CaCO}}_3\text{(s)}+2{\text{H}}^{+}\text{(aq)}\to {\text{Ca}}^{2+}\text{(aq)}+{\text{H}}_2\text{O(l)}+{\text{CO}}_2\text{(g)}$ C ${\text{Ca}}^{2+}\text{(aq)}+{\text{CO}}_3^{2-}\text{(aq)}+2{\text{H}}^{+}\text{(aq)}\to {\text{Ca}}^{2+}\text{(aq)}+{\text{H}}_2\text{O(l)}+{\text{CO}}_2\text{(g)}$ D ${\text{CO}}_3^{2-}\text{(aq)}+2{\text{H}}^{+}\text{(aq)}\to {\text{H}}_2\text{O(l)}+{\text{CO}}_2\text{(g)}$

Which structure shows the carboxylic acid with the lowest relative molecular mass? A H-C(=O)-OH B H-C(H)(H)-C(=O)-OH C H-C(=O)-H D H-O-C(H)(H)-O-H

A mixture of $2\text{ g}$ of hydrogen and $32\text{ g}$ of oxygen occupies a volume, $V$, measured at r.t.p. The gases react until there is no further change. $$2{\text{H}}_2\text{(g)}+{\text{O}}_2\text{(g)}\to 2{\text{H}}_2\text{O(l)}$$ Which reactant is in excess and what is the final volume of the mixture measured at r.t.p.?

A chemist prepares calcium nitrate. They start with $8.00\text{ g}$ of pure calcium oxide and an excess of dilute nitric acid. They produce $12.65\text{ g}$ of pure, dry anhydrous calcium nitrate crystals. What is the percentage yield of calcium nitrate? [relative atomic masses, $A_r$: $\text{Ca},40$; $\text{N},14$; $\text{H},1$; $\text{O},16$] A 54.0 B 63.2 C 67.1 D 86.8

The apparatus shown is used to investigate the electrolysis using inert electrodes of dilute sulfuric acid and concentrated aqueous sodium chloride in separate experiments. Which row shows the ratio of volume of gas collected in each test-tube?

Which statement about reactions is correct? A A reaction in which the number of bonds broken equals the number of bonds formed always has an enthalpy change, $\mathrm{\Delta }H=0$. B Combustion can be either exothermic or endothermic. C In exothermic reactions, thermal energy is transferred to the surroundings, so the temperature of the surroundings increases. D The activation energy, $E_a$, for a reaction is the minimum energy particles must have in order to collide.

The word equations for two reactions of ethene are shown.

The bond energies of the bonds involved in the reactions are shown in the table.

What is the value of $(\mathrm{\Delta }{H}_{\text{reaction1}}-\mathrm{\Delta }{H}_{\text{reaction2}})$? A $+240\text{ kJ / mol}$ B $+3\text{ kJ / mol}$ C $-3\text{ kJ / mol}$ D $-246\text{ kJ / mol}$

Two changes are described. change 1 Copper is added to concentrated nitric acid. Nitrogen dioxide is produced. change 2 Concentrated sulfuric acid is added to sugar. The change that occurs cannot be reversed. Which row is correct?

Which change increases the rate of a chemical reaction? A using a higher pressure in a gaseous reaction B using a lower temperature C using a more dilute solution D using larger pieces of a solid

In two separate experiments, 1 and 2, an excess of powdered calcium carbonate reacts in a flask with dilute hydrochloric acid. In experiment 1, the volume of carbon dioxide evolved is measured at regular time intervals. In experiment 2, the mass of the flask and its contents is measured at regular time intervals. The results of both experiments are plotted on graphs. Which graphs show the results of these two experiments?

Which statements about the Haber process for the manufacture of ammonia are correct? 1 At equilibrium, the concentrations of the reactants and products are no longer changing. 2 Increasing the pressure moves the position of equilibrium to the right. 3 Increasing the temperature moves the position of equilibrium to the left. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Acidified aqueous potassium manganate(VII) is used as a test reagent. When it is added to an aqueous solution of compound M, the colour of the test reagent changes from ......1...... . This colour change shows that M is ......2...... . Which words correctly complete gaps 1 and 2?

In a neutralisation reaction, which change in particles occurs? A $\text{atoms}\to \text{molecules}$ B $\text{ions}\to \text{molecules}$ C $\text{atoms}\to \text{ions}$ D $\text{ions}\to \text{atoms}$

Which pair of substances are both insoluble in water? A ammonium chloride and ammonium carbonate B copper carbonate and copper hydroxide C lead nitrate and lead chloride D zinc sulfate and zinc hydroxide

The atomic number of element X is 12. What is the formula of the chloride of X? A $\text{XCl}$ B ${\text{XCl}}_2$ C ${\text{XCl}}_4$ D ${\text{X}}_2\text{Cl}$

Elements P, Q, R and S are in either Group I or Group VII of the Periodic Table. P is a liquid at r.t.p. Q is a gas at r.t.p. Elements R and S both form basic oxides. Element R has a higher melting point than element S. Which pair of elements gives the most vigorous reaction? A P and R B P and S C Q and R D Q and S

Three statements about noble gases are listed. 1 Their atoms all have eight electrons in the outer shell. 2 They are unreactive because their outer shells are full. 3 They are diatomic. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 1 only D 2 only

Solid 1 and solid 2 are both elements. Solid 1 is not malleable. Solid 2 is ductile. Which statement is correct? A Solid 1 has good electrical conductivity only when molten. B Solid 2 has good electrical conductivity only when molten. C The layers of ions in solid 1 can slide over one another. D The layers of ions in solid 2 can slide over one another.

When a piece of aluminium is placed in cold, dilute hydrochloric acid, no reaction is observed initially. What is the reason for this? A Aluminium contains small amounts of a more reactive metal that reacts with the acid instead. B Aluminium is above hydrogen in the reactivity series. C Aluminium is amphoteric and will only react with bases. D Aluminium is coated with an oxide layer that prevents the acid getting to the metal.

A piece of zinc is attached to a steel car to prevent it from rusting. Which statement is correct? A A piece of copper is more effective than zinc because copper does not rust. B A piece of magnesium is more effective than zinc because magnesium is less reactive than zinc. C The piece of zinc provides a barrier around the entire steel car. D The piece of zinc provides sacrificial protection to the steel car.

Which statement about the extraction of iron from hematite in the blast furnace is correct? A Coke is reduced to carbon dioxide producing thermal energy to heat the furnace. B Hematite contains iron(III) oxide which is reduced by carbon monoxide. C Limestone is added to the blast furnace and is a substance that consists mainly of calcium oxide. D Molten slag is formed from a reaction between hematite and silicon(IV) oxide.

Water may contain many substances before it is purified for drinking. Three substances are listed. 1 dissolved oxygen 2 harmful microbes 3 insoluble solids Which substances are removed by the treatment of the domestic water supply? A 1 and 2 B 1 and 3 C 2 and 3 D 3 only

Dry air is a mixture of gases. 99% of the mixture is nitrogen and oxygen. What is in the highest abundance in the remaining 1%? A argon B chlorine C hydrogen D water vapour

Which statement about alkanes is correct? A Ethane reacts with chlorine in an addition reaction. B Propane has a higher boiling point than butane. C The molecule of the alkane that contains 99 carbon atoms has 200 hydrogen atoms. D There are three isomers with the formula ${\text{C}}_4{\text{H}}_{10}$.

Compound X is an alcohol containing only three carbon atoms. Compound Y is an alcohol containing only four carbon atoms. Both compounds have the general formula ${\text{C}}_n{\text{H}}_{2n+1}\text{OH}$. Which row shows the numbers of structural isomers of compounds X and Y that are unbranched alcohols?

Which two compounds react together to form ${\text{CH}}_3{\text{CH}}_2{\text{COOCH}}_3$? A ethanoic acid and ethanol B methanoic acid and ethanol C methanoic acid and propanol D propanoic acid and methanol

Three statements about fuels are listed. 1 Fossil fuels include coal, natural gas and wood. 2 Petroleum is a mixture of hydrocarbons. 3 Naphtha is used as a chemical feedstock. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Which statement about propene is correct? A Propene is a saturated hydrocarbon because it has a double carbon–carbon bond in its molecule. B Propene is the third member of the homologous series of alkenes. C Propene reacts with bromine in a substitution reaction that results in the rapid decolourisation of the bromine. D Propene reacts with hydrogen in the presence of a nickel catalyst to produce propane.

Copper(II) oxide reacts with dilute ethanoic acid. Which equation for this reaction is correct? A $\text{CuO}+{\text{CH}}_3\text{COOH}\to {\text{CH}}_3\text{COOCu}+{\text{H}}_2$ B $\text{CuO}+{\text{CH}}_3\text{COOH}\to {\text{CH}}_3\text{COOCu}+{\text{H}}_2\text{O}$ C $\text{CuO}+2{\text{CH}}_3\text{COOH}\to ({\text{CH}}_3\text{COO}{)}_2\text{Cu}+{\text{H}}_2$ D $\text{CuO}+2{\text{CH}}_3\text{COOH}\to ({\text{CH}}_3\text{COO}{)}_2\text{Cu}+{\text{H}}_2\text{O}$

The diagram shows the repeat unit of a polymer. Which row shows the monomer and type of polymerisation involved in making this polymer?

Which piece of apparatus is used to measure the volume of acid required to neutralise $25.0{\text{ cm}}^3$ of alkali in a titration? A beaker B burette C measuring cylinder D volumetric pipette

A mixture contains two solids, X and Y, and no other substances. X and Y are both soluble in water. The student separates X and Y using two steps. step 1 The student stirs the mixture into a beaker of cold water. What is step 2? A chromatography B crystallisation C distillation D filtration

Solid J contains cations and chloride ions. The aqueous solution of J is colourless. Two separate samples of the solution are tested. Aqueous sodium hydroxide added to the first sample produces a white precipitate. Aqueous ammonia added to the second sample produces a white precipitate. Which statement about J is correct? A The cation in J must be ${\text{Al}}^{3+}$. B The cation in J must be ${\text{Fe}}^{2+}$. C When dilute nitric acid and then aqueous barium nitrate are added to an aqueous solution of J, a white precipitate is formed. D When dilute nitric acid and then aqueous silver nitrate are added to an aqueous solution of J, a white precipitate is formed.

Solid Q reacts with dilute hydrochloric acid, producing a gas that turns limewater milky. Warming solid Q with aqueous sodium hydroxide produces a gas that turns damp red litmus paper blue. What is solid Q? A ammonium carbonate B ammonium nitrate C calcium carbonate D calcium nitrate