May/June 2021

A student needs to measure $28.2\text{ cm}^3$ of aqueous sodium bromide. Which apparatus should the student choose?

Experimental design

To prepare calcium nitrate, a chemist reacts $8.00\text{ g}$ of pure calcium oxide with an excess of dilute nitric acid. The reaction gives $12.65\text{ g}$ of pure, dry anhydrous calcium nitrate crystals. Calculate the percentage yield of calcium nitrate. [relative atomic mass values, $A_r$: Ca, $40$; N, $14$; H, $1$; O, $16$]

The mole and the Avogadro constant

The relative formula masses of four compounds are provided. A student has a $1.0\,\text{g}$ sample of each compound. Which sample includes the greatest number of moles of oxygen atoms?

The mole and the Avogadro constant

How many elements are needed to make the compound ammonium sulfate?

Elements, compounds and mixtures

When an aqueous solution containing copper(II) nitrate and silver nitrate is electrolysed using pure copper electrodes, which half-equation shows the process taking place at the anode?

Electrolysis

The diagram illustrates the electrolysis of concentrated and dilute aqueous sodium chloride with inert electrodes. Gases are formed and gathered in test-tubes W, X, Y and Z. Which statements are correct?

Electrolysis

Which cations are found in aqueous copper(II) sulfate?

Ion and ionic bonds

The following statements relate to hydrogen and its use as a fuel. Which statements are correct?

Hydrogen–oxygen fuel cells

Ethanol is made by fermenting glucose obtained from sugar cane. In some countries, ethanol is used as a fuel. Which statements are correct?

Fuels

Which of these changes would increase the rate of a chemical reaction?

Rate of reaction

Magnesium undergoes reaction with dilute sulfuric acid. $\text{Mg}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{MgSO}_4(aq) + \text{H}_2(g)$ Two separate experiments are performed 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. In each experiment, the volume of hydrogen formed is recorded. The outcomes are shown on a graph. Which graph is correct?

The mole and the Avogadro constant

What property of a liquid ester can be used to assess its purity before being used as a food flavouring?

Separation and purification

In which of these equations is the change shown for the underlined species correct? 1. (oxidation) $\underline{\text{CH}_4} + 2\text{O}_2 \rightarrow \underline{\text{CO}_2} + 2\text{H}_2\text{O}$ 2. (reduction) $2\text{H}_2\underline{\text{S}} + \text{SO}_2 \rightarrow \underline{3\text{S}} + 2\text{H}_2\text{O}$ 3. (reduction) $\text{BrO}_3^- + 5\underline{\text{Br}^-} + 6\text{H}^+ \rightarrow \underline{3\text{Br}_2} + 3\text{H}_2\text{O}$

Redox

The Haber process changes nitrogen and hydrogen into ammonia. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ Which row is right?

Reversible reactions and equilibrium

Which row gives the pH values for $0.1\,\text{mol dm}^{-3}$ solutions of ammonia, hydrochloric acid, sodium chloride and sodium hydroxide?

The characteristic properties of acids and bases

The water in a lake is acidic, and the fish are dying. The lake water must be neutralised. Which compound can be added in excess to neutralise the water in the lake?

The characteristic properties of acids and bases

Two unfinished statements about how an insoluble salt is prepared are given below. "……1…… may be used to make insoluble salts, such as ……2…… . The salt is obtained by ……3…… and is then ……4…… ." Which words fit gaps 1-4 correctly?

Preparation of salts

Ammonia is manufactured by the Haber process at a temperature of $400\,^{\circ}\text{C}$ and a pressure of $20\,000\,\text{kPa}$. The temperature is then raised to $500\,^{\circ}\text{C}$ while the pressure remains unchanged. What effects will this change have on ammonia production?

Reversible reactions and equilibrium

A list of properties that show how elements differ is given below. 1. metallic character 2. the number of electron shells in an atom 3. the number of protons in an atom 4. the total number of electrons in an atom Which two properties get larger across a period of the Periodic Table?

Arrangement of elements

Elements X and Y react together to make an ionic compound. Atoms of X contain more protons than atoms of Y. Atoms of Y contain more valence electrons than atoms of X. Which statement is correct?

Ion and ionic bonds

The elements in Group I of the Periodic Table exhibit patterns in both reactivity and melting point. Rubidium belongs to Group I. Which statement about rubidium is correct?

Group I properties

The characteristics of four substances are displayed. Which substance is a metal?

Properties of metals

What series of procedures should be followed to obtain a pure, dry sample of hydrated copper(II) sulfate, $\text{CuSO}_4\cdot5\text{H}_2\text{O}$, from a mixture containing hydrated copper(II) sulfate and calcium carbonate, $\text{CaCO}_3$?

Separation and purification

Group I elements and transition elements are metals. Student X proposes that the Group I elements are positioned above hydrogen in the metal reactivity series, whereas not every transition element is. Student Y proposes that the densities of Group I elements are less than those of the transition elements. Which students are right?

Group I properties

Tin is more reactive than lead but less reactive than iron. Which extraction method would be most appropriate for obtaining tin from its ore?

Extraction of metals

Fixing pieces of magnesium onto iron pipes buried underground can prevent the iron from corroding. Which reaction is responsible for protecting the iron from corrosion?

Corrosion of metals

Which reactions occur when aluminium is extracted from aluminium oxide using carbon electrodes?

Extraction of metals

Which statement regarding gases in the atmosphere is correct?

Solids, liquids and gases

How many moles of hydrogen chloride are produced when one mole of methane reacts with a large excess of chlorine in sunlight?

Alkanes

The dot-and-cross diagram shows compound X. Which of the following statements about compound X is correct?

Simple molecules and covalent bonds

Which of the following statements about alcohols are correct?

Alcohols

An ester is represented by the formula $\text{C}_2\text{H}_5\text{COO}\text{C}_2\text{H}_5$. Which two compounds would combine to make this ester?

Carboxylic acids

Which of the following statements about polymers is correct?

Polymers

J is a solution in water. When aqueous sodium hydroxide is added to J, a green precipitate forms. The mixture is then heated, but no gas is produced. Aluminium foil is added to the warmed mixture, and a gas is produced that changes damp red litmus paper blue. Which ions may be present in J?

Identification of ions and gases

X is a polymer. On hydrolysis, one of the products formed is substance Y, represented by $\text{CH}_3\text{CH}(\text{NH}_2)\text{COOH}$. What kind of polymer is X?

Polymers

Gas X shows the following characteristics. 1 colourless 2 it has no action on either damp red or blue litmus papers 3 it produces no change in limewater 4 flammable What is gas X?

Identification of ions and gases

Which particle has the greatest number of electrons?

Atomic structure and the Periodic Table

The diagrams illustrate the structures of two solids, P and Q. Which row is correct?

Ion and ionic bonds

What do we mean by a covalent bond?

Simple molecules and covalent bonds

The empirical formula of compound X is $\text{CH}_2$ and the relative molecular mass, $M_r$, of X is $70$. What is the molecular formula for X?

Formulae

The formula of magnesium oxide can be determined by using the fact that, when magnesium is heated, it reacts with oxygen and produces magnesium oxide. Which apparatus is used in this investigation?

Experimental design

Three nitrogen compounds and their formulae are listed: ammonia, $\text{NH}_3$; hydrazine, $\text{N}_2\text{H}_4$; hydroxylamine, $\text{NH}_2\text{OH}$. Which compound has the greatest relative molecular mass, $M_r$, and which compound has the largest percentage by mass of hydrogen?

Relative masses of atoms and molecules

The relative formula masses of four compounds are shown. A student has a $1.0\,\text{g}$ sample of each compound. Which sample contains the greatest number of moles of oxygen atoms?

The mole and the Avogadro constant

In a closed container, $10\,\text{cm}^3$ of propane is burned with $70\,\text{cm}^3$ of oxygen. $\text{C}_3\text{H}_8(g) + 5\text{O}_2(g) \rightarrow 3\text{CO}_2(g) + 4\text{H}_2\text{O}(l)$. What total volume of gas is present after the reaction? (Assume all gas volumes are measured at room temperature and pressure.)

The mole and the Avogadro constant

When a mixture made up of sodium chloride and sodium hydrogencarbonate is heated, the reaction below occurs. $2\text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s) + \text{CO}_2(g) + \text{H}_2\text{O}(g)$. On heating, sodium chloride remains unchanged. If $6.0\,\text{g}$ of the mixture is heated, the mass decreases by $1.5\,\text{g}$. What percentage by mass of the mixture is sodium hydrogencarbonate? [$M_r$: $\text{NaHCO}_3$, $84$; $\text{Na}_2\text{CO}_3$, $106$; $\text{CO}_2$, $44$; $\text{H}_2\text{O}$, $18$]

The mole and the Avogadro constant

Molten sodium chloride is electrolysed. Which change takes place at the cathode?

Electrolysis

What positive ions are contained in aqueous copper(II) sulfate?

Ion and ionic bonds

Natural gas is used as a source of energy. Which compound is the main component of natural gas?

Fuels

Ethanol is made by fermenting glucose obtained from sugar cane. In some countries, ethanol is used as a fuel. Which statements are correct?

Fuels

When aqueous sodium thiosulfate is mixed with hydrochloric acid, the rate of reaction becomes faster if the concentration of each reactant is increased. Nitrogen gas reacts with hydrogen gas, and the reaction rate also increases if the pressure in the reaction vessel is raised. Which row gives the correct explanation for why the stated change makes the reaction happen faster?

Rate of reaction

Magnesium reacts with dilute sulfuric acid: $\text{Mg}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{MgSO}_4(aq) + \text{H}_2(g)$. At $25\,^{\circ}\text{C}$, two experiments are completed. In 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. In 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 volume of hydrogen produced is recorded. The findings are shown on a graph. Which graph is the correct one?

The mole and the Avogadro constant

Which property of a liquid ester can be used to test whether it is pure before being used as a food flavouring?

Separation and purification

X is a colourless solution. A few drops of aqueous potassium iodide solution are introduced into a sample of X. There is no visible change. Y is also a colourless solution. A few drops of aqueous acidified potassium manganate(VII) solution are added to a sample of Y. The purple colour of the potassium manganate(VII) vanishes. What can be inferred about X and Y from these two observations?

Redox

Brown nitrogen dioxide combines to produce colourless dinitrogen tetroxide in a reversible reaction. The forward reaction is exothermic. $\text{2NO}_2(\text{g}) \rightleftharpoons \text{N}_2\text{O}_4(\text{g})$ Which changes would cause the equilibrium mixture to become darker in colour?

Reversible reactions and equilibrium

Which row gives the pH values for $0.1\,\text{mol dm}^{-3}$ solutions of ammonia, hydrochloric acid, sodium chloride and sodium hydroxide?

The characteristic properties of acids and bases

Four test-tubes are arranged as illustrated, containing $\text{AgNO}_3(\text{aq})$, $\text{Cu(NO}_3)_2(\text{aq})$, $\text{Pb(NO}_3)_2(\text{aq})$ and $\text{NaNO}_3(\text{aq})$. What happens when dilute hydrochloric acid is added to each test-tube? Key: $\times$ = clear solution, $\checkmark$ = precipitate formed.

Identification of ions and gases

Aqueous ammonia reacts with a compound to produce the salt ammonium phosphate. What type of reaction does ammonia undergo in order to produce ammonium phosphate?

The characteristic properties of acids and bases

Sulfuric acid is made by the contact process. A number of substances take part in this process, among them vanadium(V) oxide and water. What roles do vanadium(V) oxide and water have in the contact process?

Rate of reaction

Several properties that show the differences between elements are given below. 1 metallic nature 2 the count of electron shells in an atom 3 the count of protons in an atom 4 an atom's total number of electrons Which two properties rise across a period of the Periodic Table?

Arrangement of elements

Germanium is placed in Group IV of the Periodic Table. Its proton number is $32$. Selenium is placed in Group VI of the Periodic Table. Its proton number is $34$. From the positions of germanium and selenium in the Periodic Table, which prediction can be made?

Arrangement of elements

The proton number of caesium is $55$. Relative to lithium, caesium has a ......1...... melting point, and its reaction with water is ......2...... vigorous. Caesium has ......3...... valence electrons than lithium. Which words correctly fill gaps 1, 2 and 3?

Group I properties

Nickel is a transition element. Which of these properties does it show? 1 It is able to act as a catalyst. 2 It can conduct electricity while molten. 3 It produces coloured compounds. 4 It shows only one oxidation state in its compounds.

Transition elements

Which separation method would produce pure samples of both substances in the mixture?

Separation and purification

Which metal reacts with steam and may be obtained from its ore by reduction using carbon?

Reactivity series

Three true facts about aluminium are given below. 1 Aluminium is the most abundant metal in the Earth's crust. 2 It is expensive to obtain aluminium from its ore, bauxite. 3 The world's supply of bauxite is limited. Which of these statements give reasons why aluminium ought to be recycled?

Extraction of metals

By fastening pieces of magnesium to iron pipes buried underground, the iron can be protected against corrosion. Which reaction provides this protection?

Corrosion of metals

Iron is obtained from the ore haematite in a blast furnace. Which statement about this extraction method is correct?

Extraction of metals

Which statement is correct about how aluminium is prepared and about its properties?

Extraction of metals

How many moles of hydrogen chloride are produced when 1 mole of methane reacts with a large excess of chlorine in sunlight?

Alkanes

Vegetable oils may be converted into margarine. Which row shows the changes that occur?

Alkenes

Which of the following statements about alcohols are correct?

Alcohols

Which circled structure indicates only the functional group of a carboxylic acid?

Formulae, functional groups and terminology

Which one of these statements about polymers is correct?

Polymers

A colourless aqueous solution of J contains cations and chloride ions. When separate portions of the solution are tested, each produces a white precipitate with a few drops of aqueous sodium hydroxide and with a few drops of aqueous ammonia. Which statement about J is correct?

Identification of ions and gases

A few details about compound X are provided. X is made up of only the elements carbon, hydrogen and oxygen. When X undergoes hydrolysis, the product formed is the simple sugar glucose. What is X?

Polymers

Gas X has the following properties. 1. without colour 2. does not change either damp red or blue litmus papers 3. does not change limewater 4. can be ignited Which gas is X?

Identification of ions and gases

Which statement about states of matter is correct?

Solids, liquids and gases

Refer to the Periodic Table to answer this question. Which two particles contain the same number of electrons?

Atomic structure and the Periodic Table

The table gives information about particles W, X, Y and Z. Which statements are correct?

Atomic structure and the Periodic Table

Which dot-and-cross diagram correctly represents an ethene molecule?

Simple molecules and covalent bonds

Select your answers from the compounds below. Each compound may be used once, more than once, or not at all. The compounds are displayed as A, B, C, D, E, F and G with their structural formulae.

Formulae, functional groups and terminology

Helium, neon, argon, krypton, xenon and radon belong to Group VIII as noble gases.

Noble gases

Petroleum (crude oil) consists of a mixture of hydrocarbons.

Polymers

Copper(II) chloride, copper(II) iodide and copper(II) carbonate are all ionic compounds.

Ion and ionic bonds

Iron pyrite, $\text{FeS}_2$, is an iron ore. On heating in air, $\text{FeS}_2$ gives iron(III) oxide and sulfur dioxide.

Extraction of metals

Carbon dioxide and water vapour are both greenhouse gases present in air.

Reversible reactions and equilibrium

Aqueous ammonium nitrite, $\text{NH}_4\text{NO}_2(aq)$, breaks down on heating, as shown: $\text{NH}_4\text{NO}_2(aq) \rightarrow \text{N}_2(g) + 2\text{H}_2\text{O}(l)$.

The mole and the Avogadro constant

With proton number 47, silver is a transition element.

Transition elements

The diagram shows the structure of propenyl ethanoate.

Alkenes

Use the compounds listed below to answer the questions. They are marked A, B, C, D, E, F, G and H, and their displayed formulae are given. Each compound may be chosen once, more than once, or not chosen at all.

Formulae, functional groups and terminology

Oxygen, sulfur, selenium, tellurium and polonium belong to Group VI.

Solids, liquids and gases

People are worried about how plastics made from non-biodegradable polymers are disposed of.

Polymers

Both zinc bromide and zinc carbonate are ionic compounds.

Ion and ionic bonds

Petroleum (crude oil) supplies the starting materials used to produce ethanol and ammonia.

Fuels

Sulfur dioxide and oxides of nitrogen are substances that pollute the air.

Oxides

Sulfamic acid, $\text{NH}_2\text{SO}_3\text{H}$, is a white crystalline solid. On reaction with aqueous sodium nitrite, nitrogen gas is produced, as represented by the equation: $\text{NH}_2\text{SO}_3\text{H}(s) + \text{NaNO}_2(aq) \rightarrow \text{N}_2(g) + \text{H}_2\text{O}(l) + \text{NaHSO}_4(aq)$.

Rate of reaction

Lead is a metal whose proton number is 82.

Metallic bonding

The displayed diagram shows the structure of ethyl propenoate.

Formulae, functional groups and terminology

A student reacts dilute sulfuric acid with copper(II) carbonate to obtain a pure, dry sample of blue copper(II) sulfate crystals. Dilute sulfuric acid is colourless. Copper(II) carbonate is an insoluble green powder. The equation for the reaction is shown. $\text{H}_2\text{SO}_4\text{(aq)} + \text{CuCO}_3\text{(s)} \rightarrow \text{CuSO}_4\text{(aq)} + \text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(l)}$

Preparation of salts

A student examines how concentration affects the energy change in a neutralisation reaction. The student: - measures out $25.0\,\text{cm}^3$ of aqueous sodium hydroxide, $\text{NaOH(aq)}$, into a beaker - takes the temperature of this solution - pours $25.0\,\text{cm}^3$ of $0.10\,\text{mol dm}^{-3}$ hydrochloric acid, $\text{HCl(aq)}$, into the beaker - stirs the mixture - records the highest temperature reached by the solution in the beaker - repeats the experiment using different concentrations of hydrochloric acid.

Exothermic and endothermic reactions

A student carries out a sequence of tests on a mixture of ionic compounds in aqueous solution. Complete the table shown. Name any gases produced and describe the tests used to identify them.

Identification of ions and gases

Aqueous iron(III) nitrate mixed with aqueous sodium thiosulfate gives a purple mixture. A reaction occurs in the mixture. Once the reaction is finished, the solution changes from purple to colourless.

Rate of reaction

A student examines a solid metal carbonate by means of two separate methods.

The mole and the Avogadro constant

A student finds the concentration of dilute sulfuric acid, $\text{H}_2\text{SO}_4\text{(aq)}$, by carrying out a titration with aqueous sodium hydroxide, $\text{NaOH(aq)}$.

Acid–base titrations

Hydrated magnesium sulfate has the formula MgSO$_4\cdot x$H$_2$O. On heating, hydrated magnesium sulfate loses water of crystallisation and gives anhydrous magnesium sulfate. $\text{MgSO}_4\cdot x\text{H}_2\text{O (s)} \rightarrow \text{MgSO}_4\text{ (s)} + x\text{H}_2\text{O (g)}$

The mole and the Avogadro constant

The solution contains two different cations plus one anion.

Identification of ions and gases

A titration technique can be used to prepare soluble salts. A student carries out an experiment to obtain a pure sample of sodium chloride. Part of the procedure is shown in the diagram.

Acid–base titrations

A student is oxidising a sample of ethanol. The diagram shows some of the apparatus used.

Alcohols

The apparatus illustrated is used to compare how quickly different metals react with hydrochloric acid.

Rate of reaction