Oct/Nov 2023

In which changes do the particles become more widely spaced? 1. A gas is heated from $0\,^{\circ}\text{C}$ to $25\,^{\circ}\text{C}$. 2. Pressure is exerted on a gas at a constant temperature. 3. Steam changes into water by condensation. 4. Water turns into vapour at room temperature.

Solids, liquids and gases

The three compounds below are given: - copper(II) nitrate, $\text{Cu(NO}_3)_2$ - zinc sulfate, $\text{ZnSO}_4$ - sodium thiosulfate, $\text{Na}_2\text{S}_2\text{O}_3$ Which row shows the element that makes up the largest percentage by mass in each compound? Relative formula masses, $M_r$: $\text{Cu(NO}_3)_2 = 188$; $\text{ZnSO}_4 = 161$; $\text{Na}_2\text{S}_2\text{O}_3 = 158$

Relative masses of atoms and molecules

When $20\,\text{cm}^3$ of a gaseous alkane, X, undergoes complete combustion, $130\,\text{cm}^3$ of oxygen is needed. Both volumes are taken at r.t.p. What could X be?

Alkanes

Electrolysis is carried out on aqueous copper(II) sulfate using copper electrodes. What equation represents the reaction at the anode?

Electrolysis

Three statements about fuel cells are shown. Which of these statements are correct?

Hydrogen–oxygen fuel cells

When the conditions are suitable, nitrogen reacts with oxygen to produce $\text{N}_2\text{O}$. $2\text{N}_2(\text{g}) + \text{O}_2(\text{g}) \rightleftharpoons 2\text{N}_2\text{O}(\text{g})$ A reaction pathway diagram is given. What is the activation energy for the reverse reaction?

Exothermic and endothermic reactions

Hydrogen and bromine combine to make hydrogen bromide. $\text{H}_2 + \text{Br}_2 \rightarrow 2\text{HBr}$ The table provides bond energy data. What is the enthalpy change, $\Delta H$, for this reaction?

Exothermic and endothermic reactions

Octane, $\text{C}_8\text{H}_{18}$, belongs to the hydrocarbon family. When octane is combined with an excess of oxygen, nothing happens unless energy is added. Once energy is added, either as heat or an electric spark, the change occurs rapidly. The products formed in this change include carbon dioxide. Which detail in this description indicates that the change is a chemical change?

Physical and chemical changes

A student intends to investigate how the reaction rate changes when hydrochloric acid reacts with calcium carbonate. $\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$ Three methods are given. Which of these methods could be used to find out how the rate of reaction changes?

Rate of reaction

Aqueous bromine exists as an equilibrium mixture. $\text{Br}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) \rightleftharpoons \text{OBr}^-(\text{aq}) + \text{Br}^-(\text{aq}) + 2\text{H}^+(\text{aq})$ Aqueous bromine is orange in colour. The species on the right side of the equation are colourless. Three separate portions of the equilibrium mixture are then each given a small amount of one substance. Which row indicates how the colour of the mixture changes when each substance is added?

Reversible reactions and equilibrium

In which substance is the oxidation number of the nitrogen atom the same as that of the nitrogen atom in $\text{HNO}_2$? For the other elements in these compounds, take the following oxidation numbers: $\text{H}, +1;\ \text{F}, -1;\ \text{O}, -2.$

Redox

Information on two compounds is shown below. Both compounds have simple molecular structures. Compound data: - $\text{H}_2\text{S}$: melting point $-85\,^{\circ}\text{C}$, boiling point $-61\,^{\circ}\text{C}$ - $\text{PCl}_3$: melting point $-112\,^{\circ}\text{C}$, boiling point $76\,^{\circ}\text{C}$ Two bottles are positioned close to each other inside a large container kept at $90\,^{\circ}\text{C}$. One bottle holds $1.0\,\text{g}$ of $\text{H}_2\text{S}$, and the other holds $1.0\,\text{g}$ of $\text{PCl}_3$. A detector is located in the container $2.0\,\text{m}$ from the two bottles. The bottles are opened simultaneously. Which row gives the correct answer?

Diffusion

Limewater consists of calcium hydroxide dissolved in water. Which statement concerning limewater is correct?

The characteristic properties of acids and bases

Which two oxides are able to react with aqueous sodium hydroxide?

Oxides

A solution of sodium carbonate is introduced into tap water. A white precipitate is produced. Which ion in the tap water is responsible for the precipitate forming?

Identification of ions and gases

The defining properties of the elements vary as you move from left to right across Period 2 of the Periodic Table. On the left-hand side of the period, the charge on the ion formed by an element is: 1 equal to the group number 2 negative. Which statements are correct?

Arrangement of elements

Which of the following statements about the Group VII halogens is true?

Group VII properties

A power cable needs an element that: 1 conducts electricity 2 has a relatively low density 3 is ductile. Which of these characteristics are shown by aluminium?

Properties of metals

Which diagram shows the structure of an alloy?

Alloys and their properties

The majority of metals react with oxygen in the air to produce a metal oxide. Which metal produces a metal oxide coating that lowers its apparent reactivity?

Corrosion of metals

Which statement concerning corrosion of metals is correct?

Corrosion of metals

The metals below, together with the compounds found in their ores, are listed. metal: Al, Ca, Pb, Na, Fe, Mg compound present in ore: $\text{Al}_2\text{O}_3$, $\text{CaCO}_3$, $\text{PbS}$, $\text{NaCl}$, $\text{Fe}_2\text{O}_3$, $\text{MgCO}_3$ What kind of reaction occurs when each of these metals is extracted from its ore?

Extraction of metals

Substances may be elements, compounds, or mixtures. Which row is the correct one?

Elements, compounds and mixtures

Which statement concerning natural water sources and the domestic water supply is correct?

Water

The gases below may occur in air. 1 neon 2 carbon monoxide 3 nitrogen 4 methane Which of these gases are pollutants in the atmosphere?

Air quality and climate

Which compounds are members of the same homologous series?

Formulae, functional groups and terminology

The diagrams illustrate four possible structures of $\text{C}_4\text{H}_8$. Which of these structures show the same molecule?

Formulae, functional groups and terminology

The displayed structural formulae of two organic compounds are shown. What are the names of these compounds?

Naming organic compounds

Two fractions obtained from the separation of petroleum are the lubricating oil fraction and the kerosene / paraffin fraction. Which statement is correct?

Fuels

An incomplete equation for the reaction between propane and chlorine is shown. $\text{C}_3\text{H}_8 + \text{Cl}_2 \rightarrow \text{C}_3\text{H}_7\text{Cl} + X$ A student gives three statements about this reaction. 1 The activation energy for this reaction is provided by ultraviolet light. 2 $\text{C}_3\text{H}_7\text{Cl}$ has two different structural formulae. 3 $X$ is an acidic gas. Which of the statements are correct?

Alkanes

Glycerol is an alcohol molecule containing three -OH groups in each molecule. What equation represents the combustion of glycerol?

Alcohols

Compound X turns acidified aqueous potassium manganate(VII) colourless. Compound X has the empirical formula $\text{C}_2\text{H}_5\text{O}$. Several possible structures for X are shown. Which of these structures could be correct for compound X?

Formulae, functional groups and terminology

Which of the following statements is correct?

Elements, compounds and mixtures

The letters X, Y and Z stand for different atoms. $^{40}_{19}\text{X}\quad ^{39}_{19}\text{Y}\quad ^{40}_{20}\text{Z}$ Which statement is true?

Isotopes

A student carries out two experiments. In experiment 1, ammonium carbonate is allowed to react with dilute hydrochloric acid. In experiment 2, ammonium carbonate is heated together with aqueous sodium hydroxide. For each experiment, the gas produced is examined using damp blue litmus paper and damp red litmus paper. Which row correctly indicates the colour of both pieces of litmus paper at the end of each experiment?

The characteristic properties of acids and bases

A student gives three statements. Which of the statements are correct?

Elements, compounds and mixtures

A set of four statements about graphite, diamond and silicon(IV) oxide is given. Which of these statements are correct?

Giant covalent structures

Which row is the correct one?

Elements, compounds and mixtures

Compound Y is the sole product made when $500\,\text{cm}^3$ of ammonia reacts with $250\,\text{cm}^3$ of carbon dioxide. Every measurement is taken at r.t.p. What is the formula of Y?

The mole and the Avogadro constant

What number of sodium ions are present in $30\,\text{g}$ of sodium sulfate?

The mole and the Avogadro constant

A solid is put into a flask. The flask is heated gently, and the substance’s temperature is measured at regular intervals. The diagram shows a graph of temperature plotted against time for this experiment. At which point does the flask contain both a solid and a liquid?

Solids, liquids and gases

Chrome alum is the usual name for a salt with the formula $\text{CrK(SO}_4)_2$. What is the percentage by mass of chromium in chrome alum?

Relative masses of atoms and molecules

The equation represents how iron is obtained when iron(III) oxide is reduced. $\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$ 80 tonnes of iron(III) oxide gives 50 tonnes of iron. Calculate the percentage yield?

The mole and the Avogadro constant

Copper electrodes are used to electrolyse aqueous copper(II) sulfate. Which row gives the correct description of what happens?

Electrolysis

Hydrogen combines with chlorine to make hydrogen chloride. $\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})$ The enthalpy change, $\Delta H$, for this reaction may be worked out by using bond energies. Bond energies: $\text{H--H} = 436\,\text{kJ mol}^{-1}$, $\text{Cl--Cl} = 242\,\text{kJ mol}^{-1}$, $\text{H--Cl} = 431\,\text{kJ mol}^{-1}$. What is the value of $\Delta H$ for this reaction?

Exothermic and endothermic reactions

The reaction between nitrogen and oxygen is shown below. $\text{N}_2(\text{g}) + 2\text{O}_2(\text{g}) \rightarrow 2\text{NO}_2(\text{g})$ For the reaction shown, the enthalpy change is $+66\,\text{kJ}$. If two moles of nitrogen and two moles of oxygen are used, what is the enthalpy change?

Exothermic and endothermic reactions

Substances can undergo physical changes or chemical changes. Which process describes a chemical change?

Physical and chemical changes

Students can determine the rate of a reaction using either the ‘disappearing cross’ method or the ‘loss of mass’ method. In the ‘disappearing cross’ method, the student records how long the reaction mixture takes to turn cloudy. In the ‘loss of mass’ method, the student measures how much mass is lost in a given time interval. The rates of two reactions are being studied. Reaction 1: Warm aqueous silver nitrate is added to chlorobutane dissolved in ethanol. Two products are produced. One product is an organic compound that dissolves in ethanol and the other is silver chloride, which does not dissolve in ethanol. Reaction 2: Small pieces of solid calcium carbonate are added to dilute hydrochloric acid. Which method should be chosen for each reaction?

Rate of reaction

Hydrogen is used as a reactant in both the Haber process and in the addition reaction with alkenes. Which row is the correct one?

Alkenes

Chlorine, $\text{Cl}_2$, undergoes reaction with iron(II), $\text{Fe}^{2+}$, ions. $\text{Cl}_2 + 2\text{Fe}^{2+} \rightarrow 2\text{Cl}^- + 2\text{Fe}^{3+}$ Which of the following statements about this reaction is correct?

Redox

Which of the following statements is correct?

Elements, compounds and mixtures

A crystal of sodium chloride is put into a beaker of water and it dissolves. This process can be split into four stages. At which stages does diffusion occur?

Diffusion

Some information about three oxides, Q, R and T, is provided. Q reacts with dilute sulfuric acid to produce a salt and water. R reacts with both acids and bases to produce a salt and water. T reacts with aqueous sodium hydroxide to produce a salt and water. Using only this information, which row gives the correct classification of the three oxides?

Oxides

Which description of a hydrated substance is correct?

Elements, compounds and mixtures

A student is given five reagents: dilute hydrochloric acid; dilute sulfuric acid; dilute nitric acid; solid calcium carbonate; solid copper(II) carbonate. How many soluble salts are able to be prepared using these five reagents?

Preparation of salts

The table gives the number of electrons in a single atom of each element W, X, Y and Z. W: 9; X: 15; Y: 19; Z: 35. Which of these statements is correct?

Atomic structure and the Periodic Table

Certain properties of Group VII elements, together with the explanations for these properties, are given. Which row correctly pairs a property with its reason?

Group VII properties

Aircraft manufacture needs a metal that: 1 has a comparatively low density 2 has resistance to corrosion. Which of these properties are true of aluminium?

Properties of metals

Which diagram shows an alloy?

Alloys and their properties

A small metal sample is dropped into a large beaker of water. A very vigorous reaction takes place. Once the reaction has finished, a few drops of litmus are added to the solution. What is the metal and which colour is the solution after the litmus is added?

Group I properties

Iron rusting may be stopped by covering the iron with a different material. Which statement shows why a zinc coating is more effective than a painted coating?

Corrosion of metals

The list indicates where metal X sits in the reactivity series of metals. Na Al Fe X Cu Ag Which methods may be used to extract metal X? 1 electrolysis of the solid metal oxide 2 heating the metal oxide with carbon 3 heating the metal oxide with copper

Extraction of metals

W represents ethene, X represents air, Y represents iodine and Z represents brass. Which row gives the correct answer?

Elements, compounds and mixtures

Which statement regarding water is correct?

Water

A few compounds that may be used as fertilisers are shown below. ammonium nitrate potassium nitrate potassium phosphate sodium phosphate Three elements needed for plant growth have the atomic symbols N, P and K. For each compound, how many of these three elements are present?

Formulae

A range of methods for reducing the impact of environmental problems has been proposed. Which row is correct?

Air quality and climate

Which of the following statements about organic compounds is correct?

Formulae, functional groups and terminology

In the fractional distillation of petroleum, separate fractions are collected from the top and the bottom of the fractionating column. Compared with the fraction taken from the bottom of the fractionating column, what properties does the fraction from the top have? 1 higher viscosity 2 lower boiling point 3 lower volatility 4 shorter chain length

Fuels

A chlorine atom may substitute for a hydrogen atom in a butane molecule, $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3$, producing chlorobutane. How many distinct structural isomers of chlorobutane are possible?

Formulae, functional groups and terminology

Two statements are given. 1 During the fermentation of glucose to produce ethanol, one glucose molecule gives three molecules of ethanol. 2 In the conversion of ethanol into ethanoic acid, ethanol functions as an oxidising agent. Which row for these statements is correct?

Alcohols

Polymer X is an addition polymer. The monomer from which X is formed is but-1-ene. Polymer Y is a condensation polymer. The monomers from which Y is formed are $\text{HOCH}_2\text{CH}_2\text{OH}$ and $\text{HOOCCH}_2\text{COOH}$. Which statement about X and Y is correct?

Polymers

Which of the following statements is correct?

Elements, compounds and mixtures

The diagram displays a chromatogram. Which spot has an $R_f$ value of $0.75$?

Chromatography

Which of the following statements about the isotopes of bromine is correct?

Isotopes

Some test results for polluted river water are displayed. Which metal ion has to be present in the water?

Identification of ions and gases

Which diagram represents a section of the ionic lattice in sodium chloride?

Ion and ionic bonds

When dilute hydrochloric acid is mixed with aqueous lead(II) nitrate, a white precipitate of lead(II) chloride is produced. What is the ionic equation for this reaction?

Identification of ions and gases

Which row gives a pair of molecules in which the $M_r$ of compound X is exactly half the $M_r$ of compound Y? [$A_r$: C, $12$; Cl, $35.5$; H, $1$; O, $16$]

Relative masses of atoms and molecules

When one volume of the gaseous element, $X_2$, reacts with the same volume of gaseous hydrogen, two volumes of a gaseous hydride are produced. What formula does the hydride of X have?

The mole and the Avogadro constant

At room temperature and pressure, which reaction would result in the largest volume of carbon dioxide? [$M_r$: $\text{CaCO}_3$, $100$; $\text{Na}_2\text{CO}_3$, $106$; $\text{CuCO}_3$, $124$]

The mole and the Avogadro constant

Use the list of compounds below to answer these questions. calcium oxide carbon dioxide carbon monoxide lead chloride propan-1-ol sodium nitrate sodium sulfate sulfur dioxide water Each compound can be used once, more than once, or not at all. Identify the compound that:

Identification of ions and gases

Potassium is a Group I element in the Periodic Table. Copper is a transition element. State two physical properties of potassium that differ from those of copper.

Properties of metals

A student studies the reaction of small pieces of zinc with dilute hydrochloric acid at $25^\circ\text{C}$. The dilute hydrochloric acid is present in excess.

Rate of reaction

A concentrated aqueous solution of calcium bromide is electrolysed with graphite electrodes. Predict the substance formed at each electrode.

Electrolysis

Draw a circle around the functional group on Fig. 5.1 that is found in alkenes as well.

Polymers

The equation for the Haber process that is used to produce ammonia is given below. $\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$

Reversible reactions and equilibrium

Aqueous calcium hydroxide reacts with dilute ethanoic acid. $2\text{CH}_3\text{COOH} + \text{Ca(OH)}_2 \rightarrow (\text{CH}_3\text{COO})_2\text{Ca} + 2\text{H}_2\text{O}$ A learner reacts $25.0\,\text{cm}^3$ of $0.0100\,\text{mol dm}^{-3}$ aqueous calcium hydroxide with dilute ethanoic acid, using thymolphthalein as the indicator. Exactly $12.5\,\text{cm}^3$ of dilute ethanoic acid reacts with the $0.0100\,\text{mol dm}^{-3}$ aqueous calcium hydroxide. Calculate the concentration, in $\text{mol dm}^{-3}$, of the dilute ethanoic acid.

Acid–base titrations

Methanol is used to manufacture ethanoic acid. $\text{CH}_3\text{OH(g)} + \text{CO(g)} \rightleftharpoons \text{CH}_3\text{COOH(g)}$ The forward reaction releases heat.

Reversible reactions and equilibrium

Table 9.1 gives the melting points and relative electrical conductivities of three elements.

Giant covalent structures

Select your answers from the compounds listed below. ammonia ethanol glucose magnesium chloride magnesium oxide methane nitrogen dioxide phosphorus(V) chloride poly(ethene) sodium bromide water Each compound can be chosen once, more than once, or not used at all. Identify the compound that:

Identification of ions and gases

Chromium is a transition element, whereas sodium is an element in Group I of the Periodic Table. State two physical properties of chromium that are unlike those of sodium.

Properties of metals

A learner examines how large pieces of calcium carbonate react with dilute hydrochloric acid at $25\,^{\circ}\text{C}$. Hydrochloric acid is present in excess.

Rate of reaction

When concentrated aqueous magnesium iodide is electrolysed with graphite electrodes, what product is formed at each electrode?

Electrolysis

On Fig. 5.1, circle the functional group that reacts with aqueous bromine.

Alkenes

Steam and carbon react to make carbon monoxide and hydrogen. $\text{steam} + \text{carbon} \rightleftharpoons \text{carbon monoxide} + \text{hydrogen}$ The forward reaction absorbs energy.

Exothermic and endothermic reactions

A student carries out a titration using $20.0\,\text{cm}^3$ of $0.0250\,\text{mol dm}^{-3}$ aqueous sodium carbonate and dilute hydrochloric acid. Exactly $15.5\,\text{cm}^3$ of the dilute hydrochloric acid is required to react completely with the aqueous sodium carbonate. Calculate the concentration, in $\text{mol dm}^{-3}$, of the dilute hydrochloric acid.

The characteristic properties of acids and bases

The equation below shows how carbon monoxide reacts with hydrogen at a high temperature in a sealed container. $\text{CO}(\text{g}) + 2\text{H}_2(\text{g}) \rightleftharpoons \text{CH}_3\text{OH}(\text{g})$ (methanol) In the forward direction, the reaction is exothermic.

Reversible reactions and equilibrium

Explain, using structure and bonding, why diamond and iodine have different melting points.

Giant covalent structures

A student explores the rate of reaction between calcium carbonate and dilute hydrochloric acid. Fig. 1.1 presents part of the apparatus used by the student. The student finds the rate of reaction by measuring the volume of carbon dioxide given off in a set time.

Rate of reaction

Hydrochloric acid, $\text{HCl}$, is neutralised as it is added to aqueous potassium hydroxide, $\text{KOH}$. $\text{KOH} + \text{HCl} \rightarrow \text{KCl} + \text{H}_2\text{O}$ The reaction gives out heat. $\textbf{P}$ is aqueous potassium hydroxide. $\textbf{Q}$ is $2.24\ \text{mol}/\text{dm}^3$ hydrochloric acid. A student finds the concentration of potassium hydroxide in $\textbf{P}$. The student carries out six experiments. The student: Step 1. uses a volumetric pipette to place $25.0\ \text{cm}^3$ of $\textbf{P}$ into a plastic cup Step 2. uses a measuring cylinder to add $20\ \text{cm}^3$ of distilled water to the plastic cup Step 3. stirs the mixture in the cup with a thermometer and notes its temperature to the nearest $0.5\ ^\circ\text{C}$ Step 4. uses a burette to add $5.0\ \text{cm}^3$ of $\textbf{Q}$ to the plastic cup and stirs Step 5. records the greatest temperature reached Step 6. empties the plastic cup and washes it out with water Step 7. repeats steps $1$-$6$ using five other volumes of distilled water and $\textbf{Q}$ so that the total volume in the cup is always $50\ \text{cm}^3$. The student’s results are given in Table 2.1.

The characteristic properties of acids and bases

A student examines solution $\textbf{X}$ and solution $\textbf{Y}$. Both solutions are colourless. (a) The student carries out some tests on $\textbf{X}$. Table 3.1 records the observations the student notes for these tests.

Identification of ions and gases

Ammonium sulfate is a salt that is used in fertilisers. Ammonium sulfate is made by neutralising dilute sulfuric acid with aqueous ammonia. Plan an experiment to produce pure dry crystals of ammonium sulfate. Your plan should make use of: • common laboratory apparatus • dilute sulfuric acid • aqueous ammonia • methyl orange indicator. No other chemicals should be used. Your plan should state: • the apparatus needed • the method to use. You may include a diagram to help answer the question.

Preparation of salts

A student carries out an investigation into the electrolysis of concentrated aqueous sodium chloride. Fig. 1.1 illustrates the apparatus used by the student.

Electrolysis

When sulfuric acid, $\text{H}_2\text{SO}_4$, is mixed with aqueous sodium hydroxide, $\text{NaOH}$, it is neutralised. $$\text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$$ This reaction gives out heat. P is $1.25\,\text{mol dm}^{-3}$ aqueous sodium hydroxide. Q is dilute sulfuric acid. A student is finding the concentration of sulfuric acid in Q. The student carries out six experiments. The student: Step 1 uses a volumetric pipette to place $25.0\,\text{cm}^3$ of P into a plastic cup. Step 2 uses a measuring cylinder to add $20\,\text{cm}^3$ of distilled water to the plastic cup. Step 3 stirs the contents of the cup with a thermometer and notes the temperature to the nearest $0.5\,^{\circ}\text{C}$. Step 4 uses a burette to add $5.0\,\text{cm}^3$ of Q to the plastic cup and stirs. Step 5 records the greatest temperature reached. Step 6 empties the plastic cup and washes it with water. Step 7 repeats steps 1-6 using five different volumes of distilled water and Q so that the total volume in the cup is always $50\,\text{cm}^3$. The student’s results are shown in Table 2.1.

Experimental design

A student is studying solid Y and solution Z. Solid Y is white and has carbonate ions in it. The student carries out the tests on Y shown in Table 3.1, and some of the observations for those tests are also included.

Identification of ions and gases

Copper(II) sulfate is a salt used for killing pests on plant leaves. It is made by neutralising dilute sulfuric acid with solid copper(II) oxide. Devise an experiment to obtain pure dry crystals of copper(II) sulfate. Your plan should make use of common laboratory apparatus, dilute sulfuric acid, and solid copper(II) oxide. No other chemicals should be used.

Preparation of salts