O Level Chemistry 5070 Paper 12, May/June 2025

At temperature X, the volume of samples of hexane and pentane are not affected by changing the pressure from 1 atm to 2 atm. At temperature X, the pentane molecules are free to move. At temperature X, the hexane molecules are in fixed positions. What are the states of hexane and pentane at temperature X?

A gas is produced by a chemical reaction at one side of a laboratory. After a few minutes, the gas is detected at the other side of the laboratory. Which process explains why the gas is detected at the other side of the laboratory? A condensation B diffusion C dissolving D evaporation

Which statement is correct? A All compounds are ionic. B All compounds conduct electricity when molten. C Each atom of an element contains the same number of protons. D In a mixture of substances, the proportions of the substances are always the same.

Atoms of element Q form positive ions. An ion of Q has 10 electrons and 14 neutrons. Which statement is correct? A An atom of Q has only two occupied electron shells. B Q is a non-metal. C The atomic number of Q is 10. D The mass number of Q is greater than 24.

Which particle contains the greatest number of electrons? A ${\text{Mg}}^{2+}$ B ${\text{N}}^{3-}$ C $\text{Ne}$ D ${\text{S}}^{2-}$

The table shows data about the two isotopes in a sample of the element europium.

What is the relative atomic mass of this sample of europium? A 151.88 B 151.96 C 152.00 D 152.04

Which statement about magnesium oxide is correct? A It has a high melting point and good electrical conductivity at r.t.p. B It is made up of magnesium anions and oxygen cations. C It is an ionic compound and has good electrical conductivity when molten. D It is strongly bonded because of electrons shared between magnesium atoms and oxygen atoms.

Which statement about silicon(IV) oxide is correct? A It conducts electricity. B It has a giant covalent structure. C It is an alloy. D It is ionically bonded.

Which compound has the highest relative formula mass, $M_{\text{r}}$? [$A_{\text{r}}$: $\text{K},39$; $\text{N},14$; $\text{O},16$; $\text{Ca},40$; $\text{C},12$; $\text{Li},7$; $\text{S},32$; $\text{Mg},24$; $\text{Cl},35.5$] A calcium carbonate B lithium sulfate C magnesium chloride D potassium nitrate

$100{\text{ cm}}^3$ of ethene is completely combusted in $400{\text{ cm}}^3$ of oxygen. The volumes of both gases are measured at r.t.p. What is the final volume of gas in the mixture measured at r.t.p.? A $200{\text{ cm}}^3$ B $250{\text{ cm}}^3$ C $300{\text{ cm}}^3$ D $500{\text{ cm}}^3$

The formula of hydrated sodium carbonate is ${\text{Na}}_2{\text{CO}}_3\cdot 10{\text{H}}_2\text{O}$. What is the percentage composition by mass of oxygen in hydrated sodium carbonate? A 16.8 B 22.4 C 55.9 D 72.7

The diagram shows the electrolysis of molten lead bromide with inert electrodes. Which row identifies the particles that carry charge along each arrow?

What are the products formed at the two electrodes when aqueous copper(II) sulfate is electrolysed using copper electrodes?

Which statement about a hydrogen–oxygen fuel cell is correct? A It uses a chemical reaction that has only one product. B It works by burning hydrogen in air. C It requires a continuous input of electrical energy. D It is less efficient than a petrol engine.

A reaction pathway diagram is shown. Which equation does the reaction pathway diagram show? A $2\text{H}(\text{g})+\text{O}(\text{g})\to {\text{H}}_2\text{O}(\text{g})$ B ${\text{H}}_2(\text{g})\to 2\text{H}(\text{g})$ C ${\text{H}}_2\text{O}(\text{g})\to {\text{H}}_2\text{O}(\text{l})$ D $2\text{O}(\text{g})\to {\text{O}}_2(\text{g})$

Which process is a chemical change? A the distillation of aqueous ethanol B the evaporation of water from aqueous sodium chloride C the melting of wax D the rusting of iron

Aqueous sodium thiosulfate reacts with hydrochloric acid. The rate of the reaction increases if the concentration of both reactants is increased. Nitrogen gas reacts with hydrogen gas. The rate of the reaction increases if the pressure in the reaction vessel is increased. Which row correctly explains why the given change increases the rate of the reaction?

Magnesium reacts with dilute sulfuric acid. $$\text{Mg}(\text{s})+{\text{H}}_2{\text{SO}}_4(\text{aq})\to {\text{MgSO}}_4(\text{aq})+{\text{H}}_2(\text{g})$$ Two experiments are carried out at $25{}^{\circ }\text{C}$. experiment 1 $24.0\text{ g}$ of powdered magnesium is reacted with $100{\text{ cm}}^3$ of $1.0\text{ mol}\mathrm{/}{\text{dm}}^3$ sulfuric acid. experiment 2 $24.0\text{ g}$ of powdered magnesium is reacted with $50{\text{ cm}}^3$ of $2.0\text{ mol}\mathrm{/}{\text{dm}}^3$ sulfuric acid. During each experiment, the volume of hydrogen produced is measured at regular time intervals. The results are plotted on a graph. Which graph is correct?

Which row gives the catalyst for each of the two processes?

The diagram shows the change in pH as a strong alkali is added to a weak acid. $40{\text{ cm}}^3$ of a strong alkali is added to a weak acid and a sample of the solution is tested separately with methyl orange and thymolphthalein. Which row is correct?

Which row shows the equations for the dissociation of methanoic acid and of nitric acid?

Which statement about elements in the Periodic Table is correct? A Across a period, elements at the left-hand side of the Periodic Table are more metallic than those at the right-hand side. B Down a group, elements at the top of the group lose electrons more readily than those at the bottom of the group. C Elements in the same group of the Periodic Table have the same number of completed shells of electrons. D Elements in the same period of the Periodic Table have the same number of electrons in the outer shell.

Rubidium and caesium are both elements in Group I of the Periodic Table. Which prediction comparing rubidium and caesium is correct? A Caesium has the higher density and the greater reactivity. B Caesium has the higher density; rubidium has the greater reactivity. C Rubidium has the higher density and the greater reactivity. D Rubidium has the higher density; caesium has the greater reactivity.

Three statements about the halogens are listed. 1 All halogens are non-metallic diatomic molecules. 2 Chlorine displaces both bromine and iodine from aqueous solutions of their salts. 3 The halogens become more reactive on descending Group VII of the Periodic Table. 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 statements about neon are correct? 1 It is unreactive. 2 It has strong intermolecular forces. 3 It has a full outer shell of electrons. A 1, 2 and 3 B 1 and 3 only C 1 only D 3 only

Substance X has the following properties. ● melting point $1237{}^{\circ }\text{C}$ ● boiling point $2595{}^{\circ }\text{C}$ ● malleable ● good electrical and thermal conductivity at r.t.p. What is the structure of substance X? A giant covalent B giant ionic lattice C giant metallic lattice D simple molecular

Which statement explains why objects manufactured from aluminium corrode very slowly? A Aluminium is above hydrogen in the reactivity series. B Aluminium is below hydrogen in the reactivity series. C The objects become coated with a protective layer of aluminium nitride. D The objects become coated with a protective layer of aluminium oxide.

The iron(III) oxide used in a blast furnace contains the impurity silicon(IV) oxide, ${\text{SiO}}_2$. Which reaction removes the silicon(IV) oxide? A $3{\text{SiO}}_2+{\text{Fe}}_2{\text{O}}_3\to 2\text{Fe}+3{\text{SiO}}_3$ B ${\text{SiO}}_2+\text{C}\to \text{Si}+{\text{CO}}_2$ C ${\text{SiO}}_2+\text{CaO}\to {\text{CaSiO}}_3$ D $2{\text{SiO}}_2+{\text{N}}_2\to 2\text{Si}+2{\text{NO}}_2$

The domestic water supply is treated before it is supplied to houses. Three treatments are listed. ● sedimentation and filtration ● treatment with chlorine ● treatment with carbon Which row shows the purpose of the treatments?

Nitrates and ammonium salts are used as fertilisers. Which fertiliser contains the greatest mass of nitrogen in $50\text{ kg}$ of the compound? [$A_{\text{r}}$: $\text{H},1$; $\text{N},14$; $\text{O},16$; $\text{S},32$; $\text{Cl},35.5$; $\text{K},39$] A ${\text{NH}}_4\text{Cl}$ B ${\text{NH}}_4{\text{NO}}_3$ C $({\text{NH}}_4{)}_2{\text{SO}}_4$ D ${\text{KNO}}_3$

Which strategy reduces methane emissions? A flue gas desulfurisation B planting more trees C reduction in livestock farming D use of catalytic converters

Compound P is an alcohol with the molecular formula ${\text{C}}_4{\text{H}}_{10}\text{O}$. How many structural isomers are there of compound P? A 2 B 3 C 4 D 5

Alkanes undergo a substitution reaction with chlorine. Which row shows two correct statements about the reaction between alkanes and chlorine?

A molecule of the compound ${\text{C}}_4{\text{H}}_6$ is shown. This molecule undergoes two separate addition reactions. It undergoes an addition reaction with excess bromine and an addition reaction with steam. One molecule of ${\text{C}}_4{\text{H}}_6$ reacts with ......1...... of bromine. When ${\text{C}}_4{\text{H}}_6$ reacts with steam, ......2...... is formed. Which words complete gaps 1 and 2?

Which statement about members of the homologous series of alcohols is correct? A An alcohol with two carbon atoms in each molecule is called methanol. B Butanol can be combusted to give carbon dioxide and water only. C Ethanol is the only alcohol that can be oxidised to a carboxylic acid. D Propanol can be made by the catalysed addition of steam to ethene.

The diagram shows the structure of a compound called ethanoic anhydride. $1\text{ mol}$ of ethanoic anhydride reacts with water to form $2\text{ mol}$ of a carboxylic acid only. This carboxylic acid reacts with ethanol to form an ester. How many moles of water react with $1\text{ mol}$ of the ethanoic anhydride and what is the structure of the ester?

Four samples are analysed using paper chromatography. P, Q and R are pure substances. M is a mixture of different substances. Which substances does mixture M contain? A P, Q and R B P, Q and another substance C P and Q only D P and R only

A student is making a sample of aqueous copper(II) sulfate. The student adds an excess of copper(II) oxide powder to warm sulfuric acid and stirs the mixture. Which apparatus is used to separate aqueous copper(II) sulfate from the excess copper(II) oxide? A burette B distillation apparatus C filter funnel and paper D measuring cylinder

How can a pure sample of barium sulfate be obtained from barium carbonate? A Dissolve it in dilute hydrochloric acid, add dilute sulfuric acid, filter and crystallise. B Dissolve it in dilute hydrochloric acid, add dilute sulfuric acid, filter and wash. C Dissolve it in water, add dilute sulfuric acid, filter and crystallise. D Dissolve it in water, add dilute sulfuric acid, filter and wash.

A sample of a white powder, X, is dissolved in water. Tests are done on separate portions of this solution and the observations are shown in the table.

What is X? A aluminium chloride B aluminium sulfate C calcium chloride D calcium sulfate