Oct/Nov 2025

The pressure of a sample of air is lowered while its temperature stays constant. Which row shows the changes in the air's volume and in the spacing between the particles in the air?

Solids, liquids and gases

What is the number of atoms present in $27.0\,\mathrm{g}$ of water, $\mathrm{H_2O}$?

The mole and the Avogadro constant

A sample containing sodium hydrogencarbonate mixed with sodium chloride is heated. The reaction equation for the decomposition of sodium hydrogencarbonate on heating is shown. $\mathrm{2NaHCO_3(s) \rightarrow Na_2CO_3(s) + CO_2(g) + H_2O(g)}$. Sodium chloride does not change when heated. If $6.0\,\mathrm{g}$ of the mixture is heated and the decrease in mass is $1.5\,\mathrm{g}$, what is the percentage by mass of sodium hydrogencarbonate in the mixture? [relative molecular mass, $M_r$: $\mathrm{NaHCO_3}$, 84; $\mathrm{Na_2CO_3}$, 106; $\mathrm{CO_2}$, 44; $\mathrm{H_2O}$, 18]

Relative masses of atoms and molecules

Electrolysis is used to coat a metal statue with silver. The statue serves as an electrode in a suitable electrolyte. Which row gives the correct answer?

Electrolysis

Which row is the correct one?

Experimental design

A table provides some bond energy data. Hydrazine, $\text{N}_2\text{H}_4$, reacts with oxygen, as shown. $\text{N}_2\text{H}_4 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{N}_2$. The enthalpy change, $\Delta H$, for this reaction is found by choosing and applying data from the table. What is the value of $\Delta H$?

Exothermic and endothermic reactions

The rate of reaction between calcium carbonate and dilute hydrochloric acid is determined in three separate experiments. In experiment 1, the calcium carbonate is powdered, and an excess of hydrochloric acid is used. In experiment 2, the calcium carbonate is in lumps, and an excess of hydrochloric acid is used. In experiment 3, the calcium carbonate is in lumps, less hydrochloric acid is used, and the calcium carbonate is in excess. The outcomes of these experiments are shown. Which statement is correct?

Rate of reaction

This equation represents the reversible reaction in which nitrogen and hydrogen combine to produce ammonia. $\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$. The forward reaction gives out heat. Which statement is correct when the temperature is increased?

Reversible reactions and equilibrium

Which statement is the correct one?

Experimental design

Several characteristics of a solid oxide are given: when it reacts with dilute sulfuric acid, a salt and water are formed; it does not dissolve in water; it also reacts with aqueous sodium hydroxide. Which oxide is being described?

Oxides

Two compounds are each dissolved in water separately. When the solutions are then mixed together, no visible change is observed. Which two compounds are they?

Elements, compounds and mixtures

Which substance would diffuse the fastest?

Diffusion

A section of the Periodic Table is displayed. W, X, Y and Z are not the actual symbols for the elements. Which statement is correct?

Atomic structure and the Periodic Table

The Group I metals lithium, sodium and potassium display patterns in their melting points and in how they react with water. Which statement is correct as you move down the group from lithium to potassium?

Group I properties

Chlorine gas is passed through separate samples of aqueous potassium iodide and aqueous potassium bromide. In which of the solutions does a colour change occur?

Group VII properties

Which of the following statements about the elements in Group VIII of the Periodic Table is correct?

Noble gases

Which of the following statements is correct?

Experimental design

Which elements are the principal components of brass?

Alloys and their properties

The diagrams illustrate two ways in which metal X is applied to stop iron from rusting. A student claims that metal X must be less reactive than iron and must have a smaller proton number than iron. Which of these claims are correct?

Corrosion of metals

Aluminium is obtained from molten aluminium oxide using electrolysis. Which material is used for the electrodes in industrial extraction?

Electrolysis

Which substance is added to eliminate odours when treating domestic water supplies?

Water

Carbon dioxide, methane and oxygen are gases that take part in the carbon cycle. Which of these gases lead to global warming?

Air quality and climate

The principal constituent of mineral X is calcium carbonate, $\mathrm{CaCO_3}$. X also includes very small particles of silicon(IV) oxide, $\mathrm{SiO_2}$. No other substances are present in X. Which row identifies two statements that are correct about X?

Elements, compounds and mixtures

What number of structural isomers exist for the molecular formula $\mathrm{C_4H_9Cl}$?

Formulae, functional groups and terminology

P is a branched hydrocarbon in which the ratio of carbon atoms to hydrogen atoms is $1:2$. P has a relative molecular mass of $56$. What compound is P?

Alkanes

Which row shows the correct names of the two compounds?

Elements, compounds and mixtures

Which equation shows the reaction between ethane and chlorine when ultraviolet light is present?

Alkanes

Which compound undergoes an addition reaction with hydrogen?

Alkenes

Which of the following statements about carboxylic acids is correct?

Carboxylic acids

The structures of X and Y are displayed. X is $\text{HOOC}-(\text{CH}_2)_4-\text{COOH}$ and Y is $\text{H}_2\text{N}-(\text{CH}_2)_6-\text{NH}_2$. What is the structure of the polymer produced when X and Y react together?

Polymers

Which diagram represents a measuring cylinder?

Experimental design

The chromatogram for mixture X and the pure substances P, Q, R and S is shown. Which of the following statements is correct?

Chromatography

Sulfur dioxide is produced by warming sodium sulfite with hydrochloric acid. It is an acidic gas and is denser than air. Which arrangement of apparatus is suitable for preparing and collecting a dry sample of sulfur dioxide?

Separation and purification

The structure of hydroxylamine, $\mathrm{NH_2OH}$, is shown. Which row correctly describes hydroxylamine?

Simple molecules and covalent bonds

A colourless solution of compound W is examined separately by adding a few drops of aqueous sodium hydroxide and a few drops of aqueous ammonia. In neither test is any precipitate formed. Which cation is present in W?

Identification of ions and gases

When metals react with a non-metal to make an ionic compound, they lose electrons. Calcium reacts with hydrogen to produce the ionic compound calcium hydride, $\mathrm{CaH_2}$. How many electrons are in the outer shell of each of the two hydride ions in $\mathrm{CaH_2}$?

Ion and ionic bonds

What is one property of diamond?

Giant covalent structures

Which statement correctly describes the bonding in copper?

Metallic bonding

Aluminium ions, $\mathrm{Al^{3+}}$, react with sulfate ions, $\mathrm{SO_4^{2-}}$, to produce aluminium sulfate. Which row gives the correct empirical formula and ionic formula for aluminium sulfate?

Formulae

Which of the following statements is correct?

Experimental design

Distinct samples of water and air each occupy a volume of $30\text{ cm}^3$ at room temperature and pressure. The pressure on both samples is then raised by the same amount while they remain at room temperature. Which row shows the volumes at the higher pressure?

Solids, liquids and gases

A chemist makes calcium nitrate. They begin with $8.00\text{ g}$ of pure calcium oxide and an excess of dilute nitric acid. They obtain $12.65\text{ g}$ of dry, pure anhydrous calcium nitrate crystals. Calculate the percentage yield of calcium nitrate. [relative atomic masses, $A_r$: Ca, 40; N, 14; H, 1; O, 16]

The mole and the Avogadro constant

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

Electrolysis

Which statement concerning reactions is correct?

Physical and chemical changes

The word equations for two reactions of ethene are given below. Reaction 1: ethene + hydrogen $\rightarrow$ ethane. Reaction 2: ethene + bromine $\rightarrow$ 1,2-dibromoethane. The bond energies for the bonds used in the reactions are listed in the table. What is the value of $(\Delta H_{\text{reaction 1}} - \Delta H_{\text{reaction 2}})$?

Alkenes

Two reactions are given. Reaction 1: Copper is put into concentrated nitric acid. Nitrogen dioxide is formed. Reaction 2: Concentrated sulfuric acid is put into sugar. The reaction that happens cannot be reversed. Which row is correct?

Physical and chemical changes

Which change causes the rate of a chemical reaction to increase?

Rate of reaction

In two separate experiments, 1 and 2, powdered calcium carbonate is present in excess and is reacted in a flask with dilute hydrochloric acid. For experiment 1, the volume of carbon dioxide given off is recorded at regular time intervals. For experiment 2, the mass of the flask and its contents is recorded at regular time intervals. The findings from both experiments are shown on graphs. Which graphs represent the results of these two experiments?

Rate of reaction

Which statements concerning the Haber process used to manufacture ammonia are correct?

Fertilisers

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

Identification of ions and gases

During a neutralisation reaction, what change happens to the particles?

The characteristic properties of acids and bases

Why does a balloon filled with helium gas decrease in size when the temperature changes from $30\,^{\circ}\mathrm{C}$ to $10\,^{\circ}\mathrm{C}$?

Solids, liquids and gases

Which two substances are both insoluble in water?

Elements, compounds and mixtures

Element X has an atomic number of 12. What is the formula of the chloride formed by X?

Atomic structure and the Periodic Table

Elements P, Q, R and S each belong to Group I or Group VII of the Periodic Table. P is liquid at r.t.p. Q is gaseous at r.t.p. Elements R and S both produce basic oxides. Element R has a higher melting point than element S. Which pair of elements reacts most vigorously?

Group VII properties

Three statements about noble gases are given. Which of these statements are correct?

Noble gases

Solid 1 and solid 2 are both elements. Solid 1 is not malleable. Solid 2 is ductile. Which of the following statements is correct?

Properties of metals

When a piece of aluminium is put into cold, dilute hydrochloric acid, no reaction is seen at first. What causes this?

Reactivity series

A piece of zinc is fixed to a steel car to stop it rusting. Which statement is correct?

Corrosion of metals

Which statement concerning the extraction of iron from hematite in the blast furnace is correct?

Extraction of metals

Water can include several substances before it is made safe to drink. Three substances are shown. Which of these are taken out during treatment of the domestic water supply?

Water

Dry air consists of a blend of gases. 99% of this blend is nitrogen and oxygen. Which gas is present in the greatest amount in the remaining 1%?

Air quality and climate

Atom X has an atomic number of 19 and a nucleon number of 42, while atom Y has an atomic number of 20 and a nucleon number of 40. Which of the following statements is correct?

Atomic structure and the Periodic Table

Which statement regarding alkanes is correct?

Alkanes

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

Alcohols

Which pair of compounds combine to produce $\mathrm{CH}_3\mathrm{CH}_2\mathrm{COOCH}_3$?

Formulae, functional groups and terminology

Three statements concerning fuels are given. Which of the statements are correct?

Fuels

Which of the following statements about propene is correct?

Alkenes

Copper(II) oxide reacts with dilute ethanoic acid. Which equation correctly represents this reaction?

Preparation of salts

The diagram displays the repeat unit of a polymer. Which row gives the monomer and the type of polymerisation used to produce this polymer?

Polymers

Which apparatus is used to measure the volume of acid needed to neutralise $25.0\,\text{cm}^3$ of alkali during a titration?

Acid–base titrations

A sample consists of two solids, X and Y, with no other substances present. Both X and Y dissolve in water. The student separates X and Y in two stages. Step 1: The student adds the mixture to a beaker of cold water and stirs it. What is step 2?

Separation and purification

Solid J contains cations together with chloride ions. When dissolved in water, the solution of J is colourless. Two different samples of this solution are then tested. In the first sample, adding aqueous sodium hydroxide gives a white precipitate. In the second sample, adding aqueous ammonia gives a white precipitate. Which statement about J is correct?

Identification of ions and gases

Which ionic compound contains ions that all have the same electronic configuration?

Ion and ionic bonds

When solid Q is added to dilute hydrochloric acid, it gives off a gas that makes limewater turn milky. If solid Q is warmed with aqueous sodium hydroxide, another gas is released that turns damp red litmus paper blue. What is solid Q?

Identification of ions and gases

Which ion carries a positive charge?

Ion and ionic bonds

Which row is the correct one?

Identification of ions and gases

Powdered calcium carbonate is reacted with dilute hydrochloric acid to form calcium chloride, water and carbon dioxide. Which ionic equation, with state symbols included, is correct for this reaction?

The characteristic properties of acids and bases

Which structure represents the carboxylic acid with the smallest relative molecular mass?

Carboxylic acids

A gas mixture containing $2\text{ g}$ of hydrogen and $32\text{ g}$ of oxygen has a volume, $V$, when measured at r.t.p. The gases are allowed to react until no further change occurs. $2\text{H}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{H}_2\text{O(l)}$. State which reactant remains in excess and determine the final volume of the mixture at r.t.p.?

The mole and the Avogadro constant

Use the compounds listed below to answer the questions. compound A: CH3OH compound B: CH3CH2OH compound C: cyclopropane ring (three CH2 groups) compound D: CH3CH=CH2 compound E: CH3CH2COOCH3 compound F: CH3CH2CH2CH2COOH compound G: CH3CH=CHCOOCH3 You may use each compound once, more than once, or not use it at all.

Formulae, functional groups and terminology

Air is made up of a mixture of gases.

Air quality and climate

A Mars sulfur sample contains four isotopes, and Table 2.1 lists the percentage abundance for each isotope.

Isotopes

When sodium hydrogencarbonate is heated, it breaks down. $2\mathrm{NaHCO_3}(s) \rightarrow \mathrm{Na_2CO_3}(s)+\mathrm{H_2O}(g)+\mathrm{CO_2}(g)$

Exothermic and endothermic reactions

Fluorine, chlorine, bromine and iodine are all Group VII elements.

Group VII properties

Nickel belongs to the transition elements.

Transition elements

This question concerns the unsaturated hydrocarbon ethyne. Fig. 6.1 gives the displayed formula of ethyne: H-C≡C-H.

Alkenes

Ethene is used in the manufacture of ethanol and poly(ethene). Figure 7.1 shows ethene’s displayed formula.

Alkenes

Petroleum consists of a mixture of hydrocarbons, and most of these are alkanes.

Fuels

Anhydrous copper(II) sulfate appears as a white solid.

Identification of ions and gases

Use the compounds listed below to answer the questions. Compound A: CH3OH. Compound B: HCOOH. Compound C: CH3CH2OH. Compound D: CH3COOCH3. Compound E: cyclobutane (ring of four CH2 groups). Compound F: CH3CH2CH2CH3. Compound G: CH3CH2CH=CH2. Compound H: CH3CH2CH2COOH. Each compound may be selected once, more than once, or not selected at all.

Formulae, functional groups and terminology

Water forms an essential component of the environment.

Water

Table 2.1 lists the percentage abundances of four isotopes in a titanium sample taken from an asteroid.

Isotopes

The balanced equation for the reaction of aluminium with dilute hydrochloric acid is given here. $2Al(s)+6HCl(aq)\rightarrow2AlCl_3(aq)+3H_2(g)$. Fig. 3.1 shows a reaction pathway diagram. Reactants: $2Al(s)+6HCl(aq)$. Products: $2AlCl_3(aq)+3H_2(g)$. The energy changes are marked A and B.

Exothermic and endothermic reactions

Fluorine, chlorine, bromine and iodine are all Group VII elements.

Group VII properties

Nickel is classified as a transition element.

Transition elements

This question concerns the covalent compound hydrogen peroxide. Fig. 6.1 shows the displayed formula H-O-O-H.

Simple molecules and covalent bonds

PET is a polyester and also a condensation polymer. Figure 7.1 shows the two monomers needed to form PET: one dicarboxylic acid monomer and one diol monomer.

Polymers

Fig. 8.1 presents the displayed formula for an unsaturated carboxylic acid, X: $CH_3CH=CHCOOH$.

Carboxylic acids

Hydrated zinc chloride takes the form of a white solid.

Ion and ionic bonds

A student is separating petroleum. Fig. 1.1 illustrates how the student has set up the apparatus. Fig. 1.1 labels: thermometer, water out, water in, conical flask, petroleum, heat. Apparatus A is marked on the condenser.

Fuels

A student explores the temperature changes that occur when an acid neutralises aqueous sodium hydroxide. The ionic equation for the reaction is shown: $\mathrm{H^+ + OH^- \rightarrow H_2O}$. This reaction releases heat. The temperature change is used to work out the concentration of hydrogen ions in an acid. X is $1.60\,\mathrm{mol/dm^3}$ sodium hydroxide solution. Y is an acid with concentration $2.00\,\mathrm{mol/dm^3}$. The student: step 1 fills the burette with Y; step 2 places a plastic cup inside a beaker; step 3 uses a volumetric pipette to add $25.0\,\mathrm{cm^3}$ of X to the plastic cup; step 4 measures the starting temperature of X and writes it in Table 2.1; step 5 adds $5.0\,\mathrm{cm^3}$ of Y from the burette to the plastic cup; step 6 stirs the mixture for 30 seconds and records the mixture temperature in Table 2.1; step 7 repeats steps 5 and 6 until a total of $40.0\,\mathrm{cm^3}$ of Y has been added. Fig. 2.1 shows two thermometer readings in ^{\circ}C during the investigation.

Acid–base titrations

A student carries out a sequence of tests with aqueous solution Q and aqueous solution R.

Identification of ions and gases

Alcohols can act as fuels for heating water. Plan an experiment to find out whether methanol or ethanol gives out more thermal energy per gram when burned. In your plan, describe how an alcohol burner, as in Fig. 4.1, would be used to heat water. Use water, methanol, ethanol and ordinary laboratory apparatus only; do not use any other chemicals. Fig. 4.1 labels: alcohol burner, alcohol. Your plan should cover: the extra apparatus required; the procedure to follow and the measurements to record; how those measurements are then used to decide which alcohol releases more thermal energy per gram burned. You may include a diagram if that helps.

Experimental design

A student is studying the rate of a reaction. Fig. 1.1 shows the apparatus used by the student. Fig. 1.1 includes: 50 cm^3 of aqueous sodium thiosulfate in flask A, a stop-clock, and a cross drawn on paper placed under the flask.

Rate of reaction

A learner examines how temperature changes when an acid neutralises aqueous potassium hydroxide. The ionic equation for the reaction is shown: $\mathrm{H^+ + OH^- \rightarrow H_2O}$. This reaction releases heat. The temperature change is then used to find the concentration of hydrogen ions in an acid. X is an acid with concentration 0.80 mol/dm^3. Y is 2.0 mol/dm^3 potassium hydroxide. The learner: step 1 fills the burette with Y; step 2 places a plastic cup inside a beaker; step 3 uses a volumetric pipette to transfer 25.0 cm^3 of X into the plastic cup; step 4 measures the starting temperature of X and writes it in Table 2.1; step 5 adds 5.0 cm^3 of Y from the burette to the plastic cup; step 6 stirs the mixture for 30 seconds and enters the mixture temperature in Table 2.1; step 7 repeats steps 5 and 6 until a total of 40.0 cm^3 of Y has been added. Fig. 2.1 on page 6 shows two thermometer readings in ^{\circ}C from the experiment.

Acid–base titrations

A student carries out a set of tests with aqueous solution P and aqueous solution Q.

Identification of ions and gases

The reaction of a metal with dilute sulfuric acid is exothermic. Devise an experiment to find out whether magnesium or zinc gives out more thermal energy per gram of metal when it reacts with excess dilute sulfuric acid. You are given magnesium powder, zinc powder, dilute sulfuric acid and ordinary laboratory apparatus. Do not use any other chemicals. Your plan should state: the apparatus required; the method to follow and the measurements to make; how the measurements are used to decide which metal releases more thermal energy per gram. A diagram may be included if it helps answer the question.

Exothermic and endothermic reactions