May/June 2024

A scientist heats a liquid sample. The scientist records the sample’s temperature and draws a graph showing temperature against time. Which statements are correct?

Solids, liquids and gases

Each of the reactions shown generates hydrogen. Which reaction gives the largest volume of hydrogen, measured at room temperature and pressure?

The mole and the Avogadro constant

Four sodium hydroxide solutions are prepared by dissolving solid sodium hydroxide in distilled water. Which method produces a solution with concentration of $0.10\ \text{mol dm}^{-3}$? $[M_r:\ \text{NaOH},\ 40]$

The mole and the Avogadro constant

Which row indicates the substances that are able to be electrolysed?

Electrolysis

The apparatus shown has been arranged to electroplate a steel key with copper. The key is not coated with copper. What change is needed to electroplate the key?

Electrolysis

Ammonium nitrate is dissolved in water. $\text{NH}_4\text{NO}_3\text{(s)} \xrightarrow{\text{H}_2\text{O}} \text{NH}_4\text{NO}_3\text{(aq)} \quad \Delta H = +25\ \text{kJ mol}^{-1}$ Which statements are correct?

Exothermic and endothermic reactions

Hydrogen combines with oxygen to form water. $\text{H} - \text{H} + \text{O} = \text{O} \rightarrow \text{H} - \text{O} - \text{H}$ A table shows some bond energies. Use the data in the table to determine the enthalpy change of reaction.

Exothermic and endothermic reactions

Silicon(IV) chloride, $\text{SiCl}_4$, has a boiling point of $58^\circ\text{C}$. Which row gives the type of change when silicon(IV) chloride boils together with the reason?

Physical and chemical changes

A $2\ \text{g}$ portion of calcium carbonate reacts with dilute hydrochloric acid, as shown. $\text{CaCO}_3\text{(s)} + 2\text{HCl(aq)} \rightarrow \text{CaCl}_2\text{(aq)} + \text{CO}_2\text{(g)} + \text{H}_2\text{O(l)}$ Which alteration in conditions causes the reaction to take place more slowly?

Rate of reaction

An excess of aluminium is allowed to react with dilute hydrochloric acid. $2\text{Al} + 6\text{HCl} \rightarrow 3\text{H}_2 + 2\text{AlCl}_3$ The hydrogen produced is gathered in a gas syringe. The overall volume of hydrogen in the gas syringe is measured at two-minute intervals. The outcomes of this experiment are shown. Which statement is correct?

Rate of reaction

$157.75\ \text{g}$ of bismuth(III) chloride, $\text{BiCl}_3$, is taken to prepare $500\ \text{cm}^3$ of solution with distilled water. When in water, the aqueous bismuth(III) chloride gradually turns cloudy because it reacts with water and produces insoluble bismuth oxychloride. This reaction is reversible. $\text{BiCl}_3\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{BiOCl(s)} + 2\text{HCl(aq)}$ Which of the statements are correct? $[A_r:\ \text{Bi},\ 209;\ \text{Cl},\ 35.5]$

Reversible reactions and equilibrium

A sample of substance X is made up of iron and sulfur only. $[A_r: \text{Fe},\,56;\,\text{S},\,32]$ In which row could both statements about X be correct?

Formulae

The flow chart illustrates several of the processes and reactions involved in the production of ammonia. What are the names of process X, substance 1 and substance 2?

Fertilisers

A lot of reactions involve oxidation and reduction. Which statement is correct?

Redox

The reaction equation is shown below. $\text{Cl}_2 + 2\text{KBr} \rightarrow 2\text{KCl} + \text{Br}_2$ Which of the following statements about this reaction is correct?

Group VII properties

Which row gives both the pH and the ion present at the highest concentration in an aqueous alkali?

The characteristic properties of acids and bases

A lake contains acidic water, and the fish are dying. The water in the lake must be neutralised so that its pH is near $7$. Which compound is added in excess to neutralise the lake water?

The characteristic properties of acids and bases

In a school laboratory, which two reagents are used to prepare a sample of pure barium sulfate?

Preparation of salts

An atom of element Q has a total of $17$ electrons, while an atom of element R has a total of $19$ electrons. Which of the following statements about elements Q and R is correct?

Atomic structure and the Periodic Table

Which statements about the Group VIII noble gases are correct?

Noble gases

Iron melts only at a very high temperature. Which statement accounts for the high melting point of iron?

Metallic bonding

Which of the following statements about alloys is correct?

Alloys and their properties

An atom of chlorine, Z, has a nucleon number of $37$. Which row is the correct one?

Isotopes

The table displays the reactions of four metals, P, Q, R and S, and their oxides. What is the sequence of reactivity, starting with the most reactive metal and ending with the least reactive metal?

Reactivity series

Which reactions occur during the extraction of aluminium from aluminium oxide using carbon electrodes?

Electrolysis

NPK fertilisers are applied to promote plant growth. A solid NPK fertiliser is described by these properties: • soluble in water • forms an aqueous solution with pH $7$ Which substances are combined to produce a solid NPK fertiliser?

Fertilisers

Alkanes are saturated compounds made up of carbon and hydrogen only. Structures $1$, $2$, $3$ and $4$ are saturated hydrocarbons. Which pair of structures are isomers?

Alkanes

Which of the following statements is correct?

Elements, compounds and mixtures

Compound Q is a hydrocarbon for which no structural isomers exist. When kept in the dark, Compound Q does not cause bromine to decolourise. Which compound could Q be?

Alkanes

Which of these equations show the reactions of alkanes?

Alkanes

Ethanol can be made by using either ethene or glucose as the initial raw material. Which row is correct?

Alcohols

The diagram displays four items of apparatus that are used to measure the volume of a liquid. Which item is always filled to the same mark?

Experimental design

The chromatogram illustrated has been obtained by placing a spot of black ink at point X. Spot M comes from a blue dye in the ink. What is the $R_f$ value of this blue dye?

Chromatography

Which particles are isotopes belonging to the same element?

Isotopes

The table presents the outcomes of a set of tests on two substances, X and Y. Which row indicates the identities of the ions present in X and Y?

Identification of ions and gases

A set of statements about graphite and silicon(IV) oxide, $\text{SiO}_2$, is given. Which statement is correct?

Giant covalent structures

Several statements concerning empirical and molecular formulae are provided. Which one is correct?

Formulae

What is the relative formula mass, $M_r$, for aluminium oxide?

Relative masses of atoms and molecules

What is the number of ions present in $16.0\,\text{g}$ of anhydrous copper sulfate?

The mole and the Avogadro constant

Which sample has the greatest number of atoms?

The mole and the Avogadro constant

Which physical changes give out heat and are both exothermic?

Physical and chemical changes

The reaction equation for ammonium chloride with calcium hydroxide is given below. $\text{2NH}_4\text{Cl} + \text{Ca(OH)}_2 \rightarrow 2\text{NH}_3 + \text{CaCl}_2 + 2\text{H}_2\text{O}$ $10.7\,\text{g}$ of ammonium chloride and $14.8\,\text{g}$ of calcium hydroxide are combined and heated. The mass of calcium chloride formed is $10.0\,\text{g}$. Calculate the percentage yield of calcium chloride. $[M_r: \text{NH}_4\text{Cl},\,53.5;\ \text{Ca(OH)}_2,\,74;\ \text{CaCl}_2,\,111]$

The mole and the Avogadro constant

The diagram illustrates a simple electrolytic cell. Which arrows indicate the movement of electrons?

Electrolysis

During the electrolysis of aqueous copper(II) sulfate using copper electrodes, which changes can be seen?

Electrolysis

Which row provides the description of a hydrogen-oxygen fuel cell?

Hydrogen–oxygen fuel cells

Which statements about endothermic reactions are correct?

Exothermic and endothermic reactions

Hydrogen and chlorine combine to produce hydrogen chloride. $\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}$ Bond energy data are provided. What is the enthalpy change, $\Delta H$, for this reaction?

Exothermic and endothermic reactions

Which of the following statements is correct?

Elements, compounds and mixtures

Two reactions each give a gaseous product. The reactions are carried out separately under the same temperature and pressure conditions. In each experiment, the volume of gas produced is recorded with time, and the outcomes are shown on the graph. At which point is the rate of gas production the greatest?

Rate of reaction

The reaction between calcium oxide and carbon dioxide is reversible, and the forward reaction gives out heat. $\text{CaO}(s) + \text{CO}_2(g) \rightleftharpoons \text{CaCO}_3(s)$ Calcium oxide and carbon dioxide are put into a heated flask, and the reaction attains equilibrium. Which statement about this equilibrium is correct?

Reversible reactions and equilibrium

In the Haber process, hydrogen and nitrogen combine to produce ammonia in the presence of a catalyst. Which reactant is separated by fractional distillation, and what catalyst is used in the Haber process?

Fertilisers

What does the term tap water mean?

Elements, compounds and mixtures

When chlorine is added to aqueous sodium bromide, aqueous sodium chloride and bromine are produced. Which statement about this reaction is correct?

Group VII properties

When one mole of compound $X$ is dissolved in water, it produces two moles of ions. $X$ reacts with ammonium carbonate to produce an acidic gas. What is compound $X$?

The characteristic properties of acids and bases

Which of the following statements about weak acids is correct?

The characteristic properties of acids and bases

Which compound has the lowest solubility in water?

Water

Which statement concerning water of crystallisation is correct?

Formulae

The diagram displays part of the Periodic Table. Which element is a metal with exactly three electrons in its outer shell?

Atomic structure and the Periodic Table

The table shows a comparison of two properties of lithium and potassium. Which row is correct?

Group I properties

Which characteristics are correct for the element copper?

Properties of metals

Which of the following statements is correct?

Elements, compounds and mixtures

Which reaction occurs in the blast furnace?

Extraction of metals

Which pair of particles has: • a total charge of zero • a total mass that is nearly the same as $\frac{1}{12}$ of the mass of an atom of $^{12}\text{C}$?

Atomic structure and the Periodic Table

The presence of water may be tested using either anhydrous cobalt(II) chloride or anhydrous copper(II) sulfate. Which observation would be correct when water is present?

Identification of ions and gases

Ammonium phosphate, $(\text{NH}_4)_3\text{PO}_4$, can be used as a fertiliser. What percentage by mass is made up of the elements that promote plant growth in ammonium phosphate?

Relative masses of atoms and molecules

Which of the following statements is correct?

Elements, compounds and mixtures

How is the ester $\text{C}_3\text{H}_7\text{COO}\text{C}_2\text{H}_5$ named?

Naming organic compounds

Fractional distillation is used to separate petroleum into useful products. Which fraction here has the lowest boiling point?

Fuels

Which equation shows a substitution reaction?

Alkanes

Which row gives the smallest number of moles of oxygen required for the complete combustion of $1$ mole of the named alcohol?

The mole and the Avogadro constant

The diagram illustrates part of a polymer’s structure. Which two reagents are used to make this polymer?

Polymers

A student is measuring how quickly a fixed mass of magnesium reacts with a fixed volume of dilute hydrochloric acid. Which other pieces of apparatus are needed for this experiment?

Rate of reaction

Two titrations involving dilute hydrochloric acid and aqueous sodium hydroxide are carried out with two different indicators, methyl orange and thymolphthalein. The reaction equation is given below. $\text{HCl(aq)} + \text{NaOH(aq)} \rightarrow \text{NaCl(aq)} + \text{H}_2\text{O(l)}$ A volumetric pipette is used to transfer $25.0\,\text{cm}^3$ of dilute hydrochloric acid into a conical flask containing a few drops of indicator. Aqueous sodium hydroxide is then delivered from a burette into the dilute hydrochloric acid until the end-point is reached. For each indicator, the end-point occurs when $23.6\,\text{cm}^3$ of aqueous sodium hydroxide has been added. Which of the following statements about this experiment are correct?

Acid–base titrations

An element contains two isotopes with relative isotopic masses $x$ and $x + 2$. The diagram illustrates the arrangement of atoms in a sample of this element. What is the relative atomic mass of the sample of the element?

Isotopes

Which method is used to separate a solid mixture of copper powder and sodium chloride so that pure, solid samples of each compound are obtained?

Separation and purification

Which molecule contains just four electrons participating in covalent bonds?

Simple molecules and covalent bonds

The table gives the melting points and boiling points of four compounds, W, X, Y and Z. These four compounds are silicon(IV) oxide, ethane, bromine and a carboxylic acid with formula $\text{C}_{16}\text{H}_{32}\text{O}_2$. Which row shows the identities of W, X, Y and Z?

Solids, liquids and gases

What formula represents zinc oxide?

Formulae

Which of the following statements is correct?

Elements, compounds and mixtures

In a titration, $25.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ sodium hydroxide is exactly neutralised by $20.0\,\text{cm}^3$ of dilute sulfuric acid. $\text{2NaOH} + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$ Calculate the concentration of the dilute sulfuric acid.

Acid–base titrations

Pick your responses from the substances listed below when answering the questions. carbon chlorine glucose hydrated copper(II) sulfate iron magnesium sulfate methanoic acid methanol nickel silicon(IV) oxide vanadium(V) oxide Each substance may be used once, more than once, or not used at all. State which substance:

Elements, compounds and mixtures

When calcium carbide, $\text{CaC}_2$, comes into contact with water, it produces the flammable gas ethyne, $\text{C}_2\text{H}_2$, together with calcium hydroxide.

Formulae, functional groups and terminology

When heated, aqueous ammonium nitrite breaks down to produce nitrogen. $\text{NH}_4\text{NO}_2(\text{aq}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\text{l})$

Rate of reaction

Potassium iodide, KI, is an ionic solid made up of a lattice containing potassium ions and iodide ions.

Ion and ionic bonds

Heating a sample of zinc sulfite in a sealed system produces an equilibrium mixture. $\text{ZnSO}_3(\text{s}) \rightleftharpoons \text{ZnO}(\text{s}) + \text{SO}_2(\text{g})$ The forward reaction is endothermic.

Reversible reactions and equilibrium

Carbon dioxide is a greenhouse gas and is associated with greater global warming.

Air quality and climate

At room temperature, chlorine exists as a gas. At room temperature, iodine exists as a solid.

Solids, liquids and gases

Fig. 8.1 presents a flow chart that gives information about several organic chemical reactions.

Naming organic compounds

Polymers can be produced by either an addition reaction or a condensation reaction.

Polymers

Pick one item from the list below to respond to the questions. anhydrous copper(II) sulfate calcium carbonate carbon monoxide chlorine ethanoic acid iron methanoic acid methanol nickel silicon(IV) oxide vanadium(V) oxide A substance may be selected once, selected several times, or not selected at all.

Redox

Aluminium carbide, $\text{Al}_4\text{C}_3$, reacts with water to produce methane, $\text{CH}_4$, and aluminium hydroxide.

Alkanes

When heated, aqueous hydrogen peroxide breaks down to make oxygen. $2\text{H}_2\text{O}_2(\text{aq}) \rightarrow \text{O}_2(\text{g}) + 2\text{H}_2\text{O}(\text{l})$

Rate of reaction

Calcium bromide, $\text{CaBr}_2$, is an ionic solid made up of a lattice containing calcium ions and bromide ions.

Ion and ionic bonds

If a sample of zinc carbonate is heated in a closed system, an equilibrium mixture results. $\text{ZnCO}_3(\text{s}) \rightleftharpoons \text{ZnO}(\text{s}) + \text{CO}_2(\text{g})$ The forward reaction takes in heat.

Reversible reactions and equilibrium

Methane, nitrogen monoxide and sulfur dioxide count as air pollutants.

Air quality and climate

Oxygen exists as a gas at room temperature, whereas sulfur is a solid at room temperature.

Solids, liquids and gases

Fig. 8.1 shows a flow chart summarising several reactions of an organic compound. Compound A is butan-1-ol. In the presence of an acid catalyst, A reacts with ethanoic acid to produce ester B. A is oxidised with $\text{KMnO}_4(\text{aq})/\text{H}_2\text{SO}_4(\text{aq})$ to give compound C. Compound C is shown as a displayed formula with a four-carbon chain and a carboxylic acid group. C reacts with $\text{Na}_2\text{CO}_3(\text{aq})$ to produce D, gas E and liquid F. C also reacts with $\text{NaOH}(\text{aq})$ to give D and liquid F. When C reacts with $\text{CH}_3\text{CH}_2\text{OH}(\text{l})$ in the presence of an acid catalyst, ester G is formed.

Carboxylic acids

Polymers are formed through either an addition reaction or a condensation reaction.

Polymers

A student determines the concentration of a dilute acid, HA(aq), by titration. The student: • places $25.0\,\text{cm}^3$ of aqueous sodium hydroxide into a conical flask • adds a few drops of methyl orange indicator to the aqueous sodium hydroxide • adds HA(aq) slowly to the aqueous sodium hydroxide until the methyl orange changes colour • notes the volume of HA(aq) added.

Acid–base titrations

A student compares the reaction of four metals, A, B, C and D, with aqueous copper(II) sulfate. The four metals are each grey solids. The student: • pours $25\,\text{cm}^3$ of aqueous copper(II) sulfate into a beaker and notes its temperature • enters this temperature in Table 2.1 • adds a sample of A to the aqueous copper(II) sulfate • stirs the reaction mixture until the temperature no longer increases • measures the maximum temperature of the mixture and enters this temperature in Table 2.1 • notes any visible change in the appearance of the mixture in the beaker. The student then repeats the experiment three further times, using B, C and D instead of A. The results for D are shown in Fig. 2.1. The results for A, B and C are shown in Table 2.1. Table 2.1 metal | starting temperature / ^{\circ}C | maximum temperature / ^{\circ}C | temperature rise / ^{\circ}C A | 20 | 69.5 | 49.5 B | 24.5 | 46.0 | C | 22.0 | 61.0 | 39.0 D | | |

Reactivity series

A student carries out a sequence of experiments to examine solution R.

Identification of ions and gases

Barium carbonate breaks down on heating. The word equation for this reaction is shown. barium carbonate $\rightarrow$ barium oxide + carbon dioxide

Experimental design

A student determines the amount of iron(II) ions in a solution by titration. The student: • uses a volumetric pipette to transfer $25.0\,\text{cm}^3$ of aqueous iron(II) sulfate into a conical flask • adds about $20\,\text{cm}^3$ of dilute sulfuric acid to the flask • slowly runs aqueous potassium manganate(VII) into the conical flask until the solution just becomes pink • carries out the titration again several times.

Experimental design

A student examines how the temperature changes when a solid dissolves completely in water. The student: • measures $25\,\text{cm}^3$ of distilled water and pours it into a beaker • uses a thermometer to measure the water’s starting temperature in the beaker • writes this temperature in Table 2.1 at time $0\,\text{s}$ • adds a sample of the solid to the beaker and begins a stop-watch • stirs the mixture and notes the temperature and time every $60\,\text{s}$ for a total duration of $300\,\text{s}$. Some of the results are shown in Table 2.1.

Exothermic and endothermic reactions

A student carries out a set of experiments to investigate solution $R$.

Identification of ions and gases

Copper(II) carbonate is allowed to react with dilute sulfuric acid at room temperature. The reaction is represented by the word equation below. copper(II) carbonate + sulfuric acid $\rightarrow$ copper(II) sulfate + carbon dioxide + water Plan an experiment to find the volume of carbon dioxide produced when a known mass of copper(II) carbonate reacts completely with dilute sulfuric acid. Your plan should include common laboratory apparatus, dilute sulfuric acid and copper(II) carbonate. Do not use any other chemicals. Your plan should contain: • the apparatus required • the method to carry out and the measurements to record • ways to make the measured volume as accurate as possible. You may include a diagram to support your answer.

Experimental design