May/June 2025

The four gases below are given. 1 $\text{CH}_4$ 2 $\text{NH}_3$ 3 $\text{CO}_2$ 4 $\text{N}_2$ In what sequence do they diffuse most rapidly at room temperature and pressure?

Diffusion

Magnesium is added to aqueous copper(II) sulfate and copper is produced, together with aqueous magnesium sulfate. Which equation shows this reaction correctly?

Reactivity series

An organic compound with an $M_r$ of $88$ is given. What is its molecular formula?

Relative masses of atoms and molecules

A volume of $10\,\text{cm}^3$ of hydrogen gas is combined with $x\,\text{cm}^3$ of chlorine gas. The equation for the reaction is given below. $\text{H}_2(g) + \text{Cl}_2(g) \rightarrow 2\text{HCl}(g)$ The hydrogen is completely used up. By the end of the reaction, the total gas volume is $40\,\text{cm}^3$. All measurements are taken at room temperature and pressure. Determine the value of $x$.

The mole and the Avogadro constant

A $100\,\text{cm}^3$ portion of aqueous potassium hydroxide, with a concentration of $1.00\,\text{mol dm}^{-3}$, is reacted with excess dilute sulfuric acid. $2\text{KOH}(aq) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{K}_2\text{SO}_4(aq) + 2\text{H}_2\text{O}(l)$ A mass of $3.48\,\text{g}$ of pure anhydrous potassium sulfate is obtained. Calculate the percentage yield of potassium sulfate.

The mole and the Avogadro constant

Which statement concerning electrolysis is correct?

Electrolysis

The diagram illustrates an electrolysis experiment with inert electrodes. Which row indicates how the concentration of the electrolyte in L and in M changes as electrolysis continues?

Electrolysis

Which row is correct for a chemical reaction where $\Delta H$ is negative?

Exothermic and endothermic reactions

The diagram illustrates apparatus set up to study two different reactions that give off gases. For each experiment, the reactants are combined and the mass of the flask plus its contents is measured every $30$ seconds. A graph of mass against time is plotted. In experiment $1$, solid X is calcium carbonate. In experiment $2$, solid X is magnesium. Which graph is the correct one?

Rate of reaction

Inside a sealed flask, gases Q and R come to a dynamic equilibrium. $\text{Q}(g) \rightleftharpoons 2\text{R}(g) \qquad \Delta H \text{ is positive}$ Which change would shift the equilibrium to the right?

Reversible reactions and equilibrium

Which row gives the usual conditions employed to convert sulfur dioxide into sulfur trioxide in the Contact process?

Reversible reactions and equilibrium

Sodium is placed into water and reacts chemically. The products are hydrogen and aqueous sodium hydroxide. Which row gives the reactants and products in this reaction?

Group I properties

The pH of a dilute sample of ethanoic acid is measured. The equation showing the partial dissociation of ethanoic acid is given below. $\text{CH}_3\text{COOH}(aq) \rightleftharpoons \text{CH}_3\text{COO}^-(aq) + \text{H}^+(aq)$ Aqueous sodium ethanoate, $\text{CH}_3\text{COONa}$, is then added to the dilute ethanoic acid, and the pH is measured once more. What is the starting pH of the dilute ethanoic acid, and what happens to it after aqueous sodium ethanoate has been added?

The characteristic properties of acids and bases

Which element combines with oxygen to form an amphoteric oxide?

Oxides

Element X is located in Period 2 of the Periodic Table. X reacts with magnesium to produce an ionic compound with the formula $\text{MgX}_2$. Which element is X?

Group VII properties

Rubidium belongs to Group I of the Periodic Table. Which statement concerning rubidium is correct?

Group I properties

Which of the following statements is correct?

Elements, compounds and mixtures

M is a metal that gives coloured compounds. M can be obtained from its oxide by either heating with carbon or by electrolysis. M also reacts with dilute hydrochloric acid. Which metal is M?

Transition elements

Which statement concerning brass is correct?

Alloys and their properties

Iron is galvanised with zinc to stop rusting. What type of protection does galvanising provide?

Corrosion of metals

In a blast furnace, iron is obtained from the ore hematite. Which statement about this extraction process is correct?

Extraction of metals

Chlorine and carbon are both used to treat the domestic water supply. Which row describes one reason for using each substance?

Water

A diagram of an atom of element X is shown. Which element is X?

Atomic structure and the Periodic Table

Which row gives an adverse effect of the pollutant named?

Air quality and climate

Three statements concerning global warming and greenhouse gases are given. Which statements are correct?

Air quality and climate

Which compound is classified as an alcohol?

Alcohols

An ester is shown with the structural formula $\text{CH}_3\text{COOCH}_2\text{CH}_2\text{CH}_3$. What is the name of this ester?

Naming organic compounds

Petroleum is split into fractions in a fractionating column. Which fraction property becomes greater from the base to the top of the column?

Fuels

Three statements about alkanes are given. Which of the statements are correct?

Alkanes

The flow chart illustrates some reactions of hydrocarbons. Which row is the correct one?

Alkenes

A condensation polymer’s structure is displayed. Which pair of monomers produces this polymer?

Polymers

A titration is carried out. $25.0\,\text{cm}^3$ of aqueous sodium hydroxide is placed into a conical flask. Several drops of methyl orange indicator are then added. Dilute hydrochloric acid is added drop by drop to the mixture until the colour changes. Which row is correct?

Acid–base titrations

A sample of compound $X$ that contains impurities has a melting point of $120\,^{\circ}\text{C}$. $X$ is then purified, and its melting point is measured once more. Which row is correct?

Separation and purification

Which option gives the correct meaning of isotopes?

Isotopes

Two compounds, $P$ and $Q$, are each examined using samples. The outcome of every test is displayed. Which row gives the identities of the ions present in $P$ and $Q$?

Identification of ions and gases

A pure specimen of element X has a relative atomic mass of $51.8$. This sample contains three isotopes. The table gives the relative masses and percentage abundances for two of the isotopes: relative mass $50$ with abundance $40\%$; relative mass $55$ with abundance $20\%$. What is the relative mass of the third isotope?

Isotopes

Magnesium combines with oxygen to produce magnesium oxide. $2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$ Which row is the correct one?

Redox

Which statement concerning solid calcium chloride is correct?

Ion and ionic bonds

Which statement gives the correct description of metallic bonding?

Metallic bonding

The ions $\text{Ca}^{2+}$ and $\text{PO}_4^{3-}$ join together to make an ionic compound. What formula does the compound have?

Ion and ionic bonds

When the temperature is X, raising the pressure from $1\,\text{atm}$ to $2\,\text{atm}$ leaves the volumes of the hexane and pentane samples unchanged. At temperature X, pentane molecules are able to move freely, but hexane molecules are arranged in fixed positions. What are the states of hexane and pentane at temperature X?

Solids, liquids and gases

A volume of $100\,\text{cm}^3$ of ethene is burned completely 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.?

The mole and the Avogadro constant

Hydrated sodium carbonate has the formula $\text{Na}_2\text{CO}_3\cdot10\text{H}_2\text{O}$. What is the percentage by mass of oxygen in hydrated sodium carbonate?

Relative masses of atoms and molecules

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

Electrolysis

Which substances are formed at each electrode when aqueous copper(II) sulfate is electrolysed using copper electrodes?

Electrolysis

Which of the following statements about a hydrogen-oxygen fuel cell is correct?

Hydrogen–oxygen fuel cells

The diagram below is a reaction pathway diagram. Which equation is represented by this reaction pathway diagram?

Exothermic and endothermic reactions

Which process counts as a chemical change?

Physical and chemical changes

When aqueous sodium thiosulfate reacts with hydrochloric acid, the reaction rate rises if the concentration of each reactant is increased. When nitrogen gas reacts with hydrogen gas, the reaction rate rises if the pressure inside the reaction vessel is increased. Which row correctly states why the stated change makes the reaction rate increase?

Rate of reaction

Magnesium is allowed to react with dilute sulfuric acid. $\text{Mg(s)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{MgSO}_4\text{(aq)} + \text{H}_2\text{(g)}$ The two experiments are both done at $25\,^{\circ}\text{C}$. experiment 1: $24.0\,\text{g}$ of powdered magnesium is reacted with $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ sulfuric acid. experiment 2: $24.0\,\text{g}$ of powdered magnesium is reacted with $50\,\text{cm}^3$ of $2.0\,\text{mol dm}^{-3}$ sulfuric acid. For each experiment, the hydrogen volume is recorded at equal time intervals. These results are then shown on a graph. Which graph is correct?

Rate of reaction

Which line shows the catalyst used for each of the two processes?

Rate of reaction

A gas is formed by a chemical reaction at one end of a laboratory. After a few minutes, it is found at the opposite end of the laboratory. Which process explains why the gas is detected at the other end of the laboratory?

Diffusion

The diagram illustrates how pH changes as a strong alkali is added to a weak acid. $40\,\text{cm}^3$ of a strong alkali is introduced into a weak acid, and a sample of the resulting solution is then tested separately using methyl orange and thymolphthalein. Which row is correct?

Acid–base titrations

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

The characteristic properties of acids and bases

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

Atomic structure and the Periodic Table

Rubidium and caesium are both elements in Group I of the Periodic Table. Which comparison between rubidium and caesium is correct?

Group I properties

Three statements about the halogens are shown below. Which of these statements are correct?

Group VII properties

Which statements concerning neon are correct?

Noble gases

Substance X shows these properties: melting point $1237\,^\circ\text{C}$; boiling point $2595\,^\circ\text{C}$; malleable; good electrical and thermal conductivity at r.t.p. What structure does substance X have?

Metallic bonding

Which statement gives the reason that objects made from aluminium corrode very slowly?

Corrosion of metals

The iron(III) oxide placed in a blast furnace includes the impurity silicon(IV) oxide, $\text{SiO}_2$. Which reaction is used to remove the silicon(IV) oxide?

Extraction of metals

Domestic water is treated before it reaches homes. Three treatments are given: sedimentation and filtration; treatment with chlorine; treatment with carbon. Which row indicates the purpose of these treatments?

Water

Which statement is the correct one?

Elements, compounds and mixtures

Nitrates and ammonium salts are employed as fertilisers. Which fertiliser has the largest mass of nitrogen in $50\,\text{kg}$ of the compound? $[A_r: \text{H}, 1; \text{N}, 14; \text{O}, 16; \text{S}, 32; \text{Cl}, 35.5; \text{K}, 39]$

Relative masses of atoms and molecules

Which strategy can be used to cut methane emissions?

Air quality and climate

Compound P is an alcohol with the molecular formula $\text{C}_4\text{H}_{10}\text{O}$. What is the number of structural isomers of compound P?

Alcohols

Alkanes take part in a substitution reaction with chlorine. Which row identifies two statements that are correct about the reaction of alkanes with chlorine?

Alkanes

A molecule of the compound $\text{C}_4\text{H}_6$ is shown. This molecule takes part in two different addition reactions. It reacts by addition with excess bromine and also by addition 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 produced. Which words should go in gaps 1 and 2?

Alkenes

Which statement concerning members of the homologous series of alcohols is correct?

Alcohols

The diagram illustrates the structure of a compound named ethanoic anhydride. When $1\ \text{mol}$ of ethanoic anhydride reacts with water, $2\ \text{mol}$ of a carboxylic acid are produced only. This carboxylic acid then reacts with ethanol to make an ester. How many moles of water react with $1\ \text{mol}$ of ethanoic anhydride, and what is the structure of the ester?

Carboxylic acids

Four samples are tested by paper chromatography. P, Q and R are pure substances. M is a mixture of several different substances. Which substances are present in mixture M?

Chromatography

A student is preparing a sample of aqueous copper(II) sulfate. Excess copper(II) oxide powder is added to warm sulfuric acid, and the mixture is stirred. What apparatus is used to separate aqueous copper(II) sulfate from the extra copper(II) oxide?

Separation and purification

By what method can a pure sample of barium sulfate be prepared from barium carbonate?

Preparation of salts

Atoms of element Q form positive ions. One ion of Q contains $10$ electrons and $14$ neutrons. Which of the following statements is correct?

Atomic structure and the Periodic Table

A sample of white powder, X, is dissolved in water. Separate portions of this solution are tested, and the observations are recorded in the table. What is X?

Identification of ions and gases

Which particle has the largest number of electrons?

Atomic structure and the Periodic Table

The table gives information on the two isotopes present in a sample of the element europium. What is the relative atomic mass of this europium sample?

Isotopes

Which of the following statements about magnesium oxide is correct?

Ion and ionic bonds

Which statement regarding silicon(IV) oxide is correct?

Giant covalent structures

Of the compounds, which one has the greatest relative formula mass, $M_r$? [$A_r$: $\text{K}$, $39$; $\text{N}$, $14$; $\text{O}$, $16$; $\text{Ca}$, $40$; $\text{C}$, $12$; $\text{Li}$, $7$; $\text{S}$, $32$; $\text{Mg}$, $24$; $\text{Cl}$, $35.5$]

Relative masses of atoms and molecules

Select one salt from the list below to answer the questions. aluminium chloride barium sulfate calcium chloride copper(II) sulfate magnesium chloride potassium iodide potassium manganate(VII) silver nitrate sodium bromide sodium sulfite Each salt may be used once, more than once, or not used at all. State which salt should be chosen:

Identification of ions and gases

Graphite electrodes are used to electrolyse a concentrated aqueous solution of copper(II) bromide.

Electrolysis

Fig. 3.1 displays the equation for the reaction of methane with chlorine. In Fig. 3.1, methane reacts with chlorine to produce chloromethane and hydrogen chloride. Table 3.1 gives some bond energies.

Alkanes

Ethanol, $\text{C}_2\text{H}_5\text{OH}$, belongs to the homologous series of alcohols.

Alcohols

Vehicles running on petrol release a number of air pollutants.

Air quality and climate

Chlorine, $\text{Cl}_2$, belongs to Group VII in the Periodic Table.

Group VII properties

Aluminium is used to make aircraft and food containers. It resists corrosion when exposed to water and oxygen.

Corrosion of metals

Fig. 8.1 presents the displayed formula for methylbut-2-enoate.

Alkenes

Select the required answers from the salts listed below. aluminium sulfate barium chloride copper(II) nitrate copper(II) sulfate magnesium chloride potassium iodide potassium manganate(VII) silver chloride sodium bromide Each salt may be chosen once, more than once, or not chosen at all. State the salt:

Identification of ions and gases

Graphite electrodes are used to electrolyse a dilute aqueous solution of magnesium chloride.

Electrolysis

Fig. 3.1 shows the equation for the reaction of ethene with bromine.

Alkenes

Ethanoic acid, CH$_3$COOH, belongs to the homologous series of carboxylic acids.

Carboxylic acids

Some power stations rely on the combustion of fossil fuels.

Separation and purification

Bromine, Br$_2$, is placed in Group VII of the Periodic Table.

Solids, liquids and gases

Iron is the main metal used in stainless steel. Stainless steel is chosen for cutlery because it resists rusting.

Alloys and their properties

Fig. 8.1 presents the displayed formula for compound A.

Formulae, functional groups and terminology

A student finds the solubility of solid ammonium chloride in water at 60^{\circ}C. The student: step 1 places $100\text{ cm}^3$ of water in a beaker step 2 warms the water step 3 determines the mass of a weighing bottle that contains ammonium chloride step 4 puts some of this ammonium chloride into the water step 5 mixes the contents to make the solid dissolve step 6 repeats steps 4 and 5 until a small quantity of solid is still undissolved in the beaker step 7 measures the mass of the weighing bottle and the ammonium chloride left over step 8 works out the mass of ammonium chloride added to the water.

Experimental design

Sample A is an impure form of calcium carbonate. A student works out the amount in moles of calcium carbonate present in a sample of A.

Acid–base titrations

A student examines two aqueous samples, W and X.

Identification of ions and gases

Q consists of solid magnesium oxide mixed with solid barium sulfate. Magnesium oxide does not dissolve in water. When it reacts with dilute hydrochloric acid, a solution of magnesium chloride is produced. Barium sulfate does not dissolve in water and does not react with dilute hydrochloric acid.

Separation and purification

A student carries out an investigation into how the solubility of solid potassium nitrate changes with temperature. The student: step 1 places 100 cm$^3$ of water in a beaker at room temperature step 2 finds the mass of the beaker containing the water step 3 puts some potassium nitrate into the water step 4 stirs the mixture until every part of the potassium nitrate has dissolved step 5 repeats steps 3 and 4 until a small amount of solid is still undissolved in the beaker step 6 finds the mass of the beaker containing the water and potassium nitrate step 7 repeats steps 1 to 6 with water at different temperatures step 8 works out the mass of potassium nitrate dissolved in the water at each temperature.

Experimental design

Solid W is an impure organic acid, $\text{H}_3\text{A}$. To find the mass of $\text{H}_3\text{A}$ present in a sample of W, a student carries out a titration using $0.100\ \text{mol dm}^{-3}$ sodium hydroxide, NaOH. The student: step 1 puts the sample of W into a beaker step 2 adds 100 cm$^3$ of distilled water to the beaker with a measuring cylinder step 3 mixes until all of the solid has dissolved completely step 4 gives this mixture the label X step 5 uses a pipette to transfer 25.0 cm$^3$ of NaOH into a conical flask and adds five drops of phenolphthalein indicator step 6 pours X into the burette step 7 runs X into the conical flask until the solution just alters colour step 8 carries out the titration two further times.

Acid–base titrations

A student examines solid A and aqueous solution B. Solid A is a metal carbonate. Solution B has only one cation and one anion.

Identification of ions and gases

Q consists of solid copper(II) carbonate mixed with solid lead sulfate. Lead sulfate does not dissolve in water and shows no reaction with dilute sulfuric acid. Copper(II) carbonate is insoluble in water. When it reacts with dilute sulfuric acid, copper(II) sulfate solution is produced.

Separation and purification