May/June 2019

A reaction rate experiment is carried out for calcium carbonate reacting with dilute hydrochloric acid. The gas produced is gathered in a gas syringe. Which other pieces of apparatus are needed to find how the reaction rate varies with temperature and the quantity of acid used?

Rate of reaction

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

Ion and ionic bonds

During a volumetric titration, $25.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ sodium hydroxide neutralises exactly $20.0\,\text{cm}^3$ of sulfuric acid. $2\text{NaOH} + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$ Determine the concentration of the sulfuric acid?

Acid–base titrations

The equation for turning bromoethane into ethanol is given below. $\text{C}_2\text{H}_5\text{Br} + \text{NaOH} \rightarrow \text{C}_2\text{H}_5\text{OH} + \text{NaBr}$ During an experiment, $10.90\,\text{g}$ of bromoethane is changed into $3.45\,\text{g}$ of ethanol. Calculate the percentage yield of ethanol. $[M_r:\ \text{C}_2\text{H}_5\text{Br},\ 109;\ \text{C}_2\text{H}_5\text{OH},\ 46]$

The mole and the Avogadro constant

A sample of one mole of a sugar, $(\text{CH}_2\text{O})_6$, is combusted completely. What volume of oxygen, measured at room temperature and pressure, is needed for complete combustion of the sugar?

The mole and the Avogadro constant

Which statement regarding the purification of copper using electrolysis is correct?

Electrolysis

In aqueous copper(II) sulfate, which negative ions are present?

Ion and ionic bonds

The diagram illustrates the energy profile for a reaction. Which statement concerning this reaction is correct?

Exothermic and endothermic reactions

The table gives the energy released when some compounds undergo complete combustion. Which compound gives out the smallest amount of energy when $1\,\text{g}$ is completely burned?

Fuels

In three experiments, an equal mass of magnesium is allowed to react with the same volume of dilute sulfuric acid at room temperature. The magnesium is present in excess. experiment 1: Magnesium is used in large pieces. experiment 2: Magnesium is used in small pieces. experiment 3: Magnesium is used in large pieces, but the acid concentration is increased. Graphs showing the results are given. Which row is the correct one?

Rate of reaction

The equations represent four reversible reactions. For which reaction would the position of equilibrium shift to the right when both the pressure and the temperature are increased?

Reversible reactions and equilibrium

Once the solution of $X$ has been acidified using dilute nitric acid, it reacts with aqueous silver nitrate and forms a white precipitate. What might $X$ be?

Identification of ions and gases

Gas X changes acidified potassium manganate(VII) from purple to colourless. Gas Y changes aqueous potassium iodide from colourless to brown. What do these observations indicate about gas X and gas Y?

Redox

Why is ethanoic acid referred to as a weak acid?

The characteristic properties of acids and bases

What is the most suitable method for obtaining a pure sample of copper(II) sulfate?

Preparation of salts

What percentage by mass of nitrogen is present in ammonium nitrate, $\text{NH}_4\text{NO}_3$?

Relative masses of atoms and molecules

A student puts forward three statements about the Haber process and the Contact process. 1. Just one of the processes uses a raw material that is obtained by fractional distillation of air. 2. Just one of the processes makes use of a catalyst. 3. The product formed in each catalysed reaction has a formula of the type $XY_3$. Which statements are correct?

Reversible reactions and equilibrium

Which of these uses of sulfuric acid are correct? 1. used as a bleach in the production of wood pulp for paper 2. used as a preservative for tinned foods 3. used as a raw material for making detergents 4. used for use as a fertiliser

The characteristic properties of acids and bases

Element X can form: • a covalent compound, $\text{H}_2\text{X}$ • an ionic compound, $\text{Na}_2\text{X}$ • the oxides $\text{XO}_2$ and $\text{XO}_3$. Which group of the Periodic Table does X belong to?

Arrangement of elements

What property is shared by $^{40}\text{Ca}$, $^{39}\text{K}$ and $^{23}\text{Na}$?

Isotopes

Palladium is an element with atomic number 46. From where it is placed in the Periodic Table, some of its properties, together with the properties of its compounds, can be predicted. Which row is correct?

Atomic structure and the Periodic Table

Three separate elements react by giving up electrons. The ions produced each have the electronic configuration $2,8$. Which statement about these elements is correct?

Atomic structure and the Periodic Table

A paper chromatography experiment is used to separate and identify the mixture of amino acids formed when a protein is hydrolysed. Which apparatus is required?

Chromatography

A power cable needs a material that: 1. can conduct electricity 2. has a fairly low density 3. is resistant to oxidation in air. Which of these requirements does aluminium meet?

Properties of metals

A list of atmospheric pollutants is given below. 1. sulfur dioxide 2. methane 3. nitrogen dioxide 4. unburned hydrocarbons Which of these substances could be removed by being made to react with calcium carbonate?

Oxides

River water contains numerous impurities. Which process by itself can produce pure water from river water?

Separation and purification

Compound Q is a hydrocarbon with no isomers. In the dark, compound Q does not decolourise bromine. Which compound could be Q?

Alkanes

Which organic compound needs the smallest number of moles of oxygen for the complete combustion of 1 mole of the compound?

Fuels

When a molecule of a saturated hydrocarbon is cracked, it produces two molecules, X and Y. Which row is correct?

Alkanes

The displayed structures and names for three alcohols, P, Q and R, are shown below. The structures may not have been given the right names. Which structures have been named correctly?

Naming organic compounds

State the empirical formula of ethanoic acid.

Formulae, functional groups and terminology

What is the structural formula of propyl methanoate?

Naming organic compounds

Identify the substance that produces oxides of nitrogen on combustion.

Oxides

Under which conditions will a gas diffuse at the highest rate?

Diffusion

The monomer used in the manufacture of polystyrene is shown. Polystyrene is formed by which type of polymerisation, and what could be a possible partial structure of the polymer?

Polymers

Cobalt is a transition element. A cobalt particle has 24 electrons and a nucleon number of 60. Which statement about this particle is correct?

Atomic structure and the Periodic Table

Diamond and graphite are two distinct forms of the element carbon. They are used for different purposes. Which row is correct?

Giant covalent structures

Which diagram represents the outer electron arrangement in calcium fluoride?

Ion and ionic bonds

How many shared pairs of electrons are present in an ammonia molecule?

Simple molecules and covalent bonds

A pair of statements about metals is shown below. 1. Metals consist of a lattice of negative ions within a ‘sea of electrons’. 2. The electrical conductivity of metals is linked to how freely the electrons can move in the structure. Which statement is correct?

Metallic bonding

The diagrams illustrate four distinct ways of gathering gases. Which method is appropriate for collecting a gas with the properties described?

Identification of ions and gases

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

The characteristic properties of acids and bases

What mass of carbon would contain the same number of atoms as $16.0\,\text{g}$ of sulfur?

The mole and the Avogadro constant

A volume of $3.0\,\text{dm}^3$ of sulfur dioxide is reacted with $2.0\,\text{dm}^3$ of oxygen. $2\text{SO}_2(g) + \text{O}_2(g) \rightarrow 2\text{SO}_3(g)$ If the reaction is allowed to go to completion and every gas is at room temperature and pressure, what volume of sulfur trioxide is produced?

The mole and the Avogadro constant

A sample of magnesium hydroxide, $\text{Mg(OH)}_2$, is prepared by adding an excess of aqueous sodium hydroxide to an aqueous solution containing $1.20\,\text{g}$ of magnesium sulfate, $\text{MgSO}_4$. The mass of magnesium hydroxide obtained is $0.26\,\text{g}$. Calculate the percentage yield of magnesium hydroxide.

The mole and the Avogadro constant

During electrolysis of concentrated aqueous sodium chloride with inert electrodes, what substance is produced at the cathode, and what substance is produced at the anode?

Electrolysis

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

Identification of ions and gases

The diagram illustrates the energy profile for a chemical reaction. Which row is right?

Exothermic and endothermic reactions

The table gives the energy released when some compounds undergo complete combustion. Which compound gives out the smallest amount of energy when $1\,\text{g}$ is completely burned?

Fuels

An experiment is done to determine the rate of reaction between magnesium and dilute hydrochloric acid under two different conditions. In both experiments, the mass of magnesium and the number of moles of hydrochloric acid are identical. Graphs showing the results are displayed. Which statements might account for the difference between graph 1 and graph 2?

Rate of reaction

Hydrogen peroxide breaks down slowly at room temperature. $2\text{H}_2\text{O}_2(aq) \rightarrow 2\text{H}_2\text{O}(l) + \text{O}_2(g)$ This reaction may be catalysed by adding manganese(IV) oxide. Which statement is correct when a catalyst is added to the aqueous hydrogen peroxide?

Rate of reaction

When the colourless solution of X is acidified with dilute nitric acid and then mixed with aqueous silver nitrate, a white precipitate is formed. What substance could X be?

Identification of ions and gases

Reduction may be described using the gain or loss of oxygen, hydrogen or electrons. Which row gives the correct description of all three definitions of reduction?

Redox

Why is ethanoic acid classed as a weak acid?

The characteristic properties of acids and bases

Which method is most suitable for preparing a sample of silver chloride?

Preparation of salts

Urea, a nitrogenous fertiliser, has the structure shown. What is the percentage by mass of nitrogen in it?

Relative masses of atoms and molecules

Ammonia is produced by the Haber process. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) \quad \Delta H = -92\,\text{kJ mol}^{-1}$ For this reaction, which rows show a statement that is true and a reason that is correct?

Reversible reactions and equilibrium

Which of these uses of sulfuric acid are correct? 1 used as a bleach in the manufacture of wood pulp for paper 2 used as a food preservative in tinned foods 3 used as a raw material in the manufacture of detergents 4 used as a fertiliser

Fertilisers

Element X has atomic number 12. What formula represents the chloride of X?

Ion and ionic bonds

What shared property do $^{40}\text{Ca}$, $^{39}\text{K}$ and $^{23}\text{Na}$ all have?

Properties of metals

Which of the following statements about transition elements is correct?

Transition elements

Three different elements undergo reaction by losing electrons. The ions produced each have the electronic configuration $2,8$. Which statement about these elements is correct?

Atomic structure and the Periodic Table

The diagram shows a chromatogram of the colourless acids found in a drink. The chromatogram has been treated with a locating agent. A table of $R_f$ values for the possible acids is given. Which acids are present in the drink?

Chromatography

Copper displaces metal M from aqueous M nitrate. Which statement about metal M and its compounds is correct?

Reactivity series

Which of the following statements about some gases found in air is correct?

Solids, liquids and gases

Which treatment process is used for water disinfection?

Water

A molecule of compound Q contains only three C-C single bonds and ten C-H bonds, with no additional bonds present. Which statement about compound Q is correct?

Alkanes

Which organic compound needs the smallest number of moles of oxygen for the complete combustion of 1 mole of the compound?

Fuels

Which one of the reactions is an addition reaction?

Alkenes

Two equations concerning ethanol are given below. 1 ethanol + oxygen $\xrightarrow{\text{oxidation}}$ carboxylic acid 2 glucose $\xrightarrow{\text{fermentation}}$ ethanol + carbon dioxide Which row is correct?

Alcohols

What empirical formula does ethanoic acid have?

Formulae

Which structure corresponds to propyl methanoate?

Naming organic compounds

Monomer Z is used to produce poly(chloroethene). The diagram illustrates monomer Z reacting to form part of the structure of poly(chloroethene). What is monomer Z?

Polymers

At the same temperature and pressure, which gas diffuses most quickly?

Diffusion

Terylene, a man-made fibre, is used in the production of clothing. Which row gives the correct description of how Terylene is manufactured?

Polymers

The particles $\text{K}^+$ and Ar may be written as $^{39}_{19}\text{K}^+$ and $^{40}_{18}\text{Ar}$. Which of the following statements about these particles is correct?

Atomic structure and the Periodic Table

A mineral deposit is discovered to include tiny grains consisting entirely of the element carbon. Which property will certainly be true of the carbon grains?

Elements, compounds and mixtures

Which diagram shows the arrangement of outer electrons in calcium fluoride?

Ion and ionic bonds

How many pairs of electrons are shared in a single carbon dioxide molecule?

Simple molecules and covalent bonds

Two statements concerning metals are provided. 1 Metals have a lattice of negative ions within a ‘sea of electrons’. 2 The electrical conductivity of metals depends on the mobility of the electrons in the structure. Which statement is correct?

Metallic bonding

Select answers from the particles listed below. The particles listed are: $^{79}_{35}\text{Br}$, $^{35}_{17}\text{Cl}$, $^{37}_{17}\text{Cl}$, $^{23}_{11}\text{Na}$, $^{17}_{8}\text{O}$, $^{39}_{20}\text{Ca}$, $^{37}_{17}\text{Cl}^-$, $^{64}_{29}\text{Cu}$, $^{20}_{10}\text{Ne}$, $^{18}_{8}\text{O}^{2-}$. A particle may be used once, more than once, or not at all.

Atomic structure and the Periodic Table

Cyclobutane and butene are both examples of hydrocarbons.

Alkenes

The table presents some of the properties of the elements in Group II of the Periodic Table.

Arrangement of elements

Molybdenum, Mo, belongs to the transition elements.

Transition elements

Air contains many different gases.

Air quality and climate

Acid U is a compound made up of carbon, hydrogen and oxygen.

The mole and the Avogadro constant

Propanoic acid is a weak acid, while calcium hydroxide and calcium oxide are bases.

The characteristic properties of acids and bases

Ammonium carbonate, $(\text{NH}_4)_2\text{CO}_3$, is a white solid that breaks down on heating. $(\text{NH}_4)_2\text{CO}_3(s)\rightarrow2\text{NH}_3(g)+\text{CO}_2(g)+\text{H}_2\text{O}(g)$

Identification of ions and gases

A scientist warms a sample of phosphorus(V) chloride in a sealed container. Dynamic equilibrium is reached. $\text{PCl}_5(g)\rightleftharpoons\text{PCl}_3(g)+\text{Cl}_2(g)$

Reversible reactions and equilibrium

Food packaging generates a great deal of waste. This waste contains both plastic and glass.

Polymers

Select from the particles listed to answer the questions. Particles available: CH$_4$, Cl$^-$, Fe$^{2+}$, H$^+$, H$_2$S, MnO$_4^-$, NH$_4^+$, P$^{3-}$. Any particle may be used once, more than once, or not at all.

Atomic structure and the Periodic Table

The structures of cyclobutanol and butanoic acid are displayed.

Formulae, functional groups and terminology

The table summarises several properties of the elements in Group III of the Periodic Table. Element / proton (atomic) number / atomic radius (nm) / melting point (^{\circ}C) B: 5, 0.080, 2306 Al: 13, 0.125, 660 Ga: 31, 0.125, 30 In: 49, 0.150, 157 Tl: 81, 0.155, 304 Nh: 113, not given, not given

Arrangement of elements

Titanium, Ti, belongs to the metallic elements.

The mole and the Avogadro constant

Petroleum (crude oil) is an important source for many chemicals.

Fuels

W is a compound made up of carbon, hydrogen and oxygen.

Formulae

Drinking water is produced by purifying sea water and river water.

Water

Ammonium iodide, NH$_4$I, is a white solid that decomposes on heating. $\text{NH}_4\text{I(s)} \rightarrow \text{NH}_3(g) + \text{HI}(g)$

Identification of ions and gases

Nitrogen monoxide combines with oxygen to produce nitrogen dioxide. If this reaction is examined in a closed system, dynamic equilibrium is reached. $\text{2NO}(g) + \text{O}_2(g) \rightleftharpoons \text{2NO}_2(g)$

Reversible reactions and equilibrium

A waste sample contains plastic and copper.

Polymers

Ammonium sulfate is a salt used as a fertiliser. A student is making some ammonium sulfate crystals by neutralisation. She uses dilute sulfuric acid together with aqueous ammonia. The diagrams show some of the apparatus available to the student.

Preparation of salts

Iron rusts in the presence of air and water, producing a solution that contains aqueous iron(III) ions. If an indicator is added to a solution containing aqueous iron(III) ions, it becomes dark blue. A student investigates how sodium chloride affects the rate at which iron rusts.

Rate of reaction

A student has three colourless liquids, A, B and C. She is told that the liquids are hexene, ethanol and ethanoic acid. Her task is to identify A, B and C.

Formulae, functional groups and terminology

A sample of river water is examined for pollutants.

Identification of ions and gases

A liquid hydrocarbon is ignited in the apparatus shown.

Acid–base titrations

A student carries out an electrolysis experiment to investigate how the time for which an electric current is passed through $1\text{ mol dm}^{-3}$ copper(II) sulfate affects the mass of the cathode.

Electrolysis

Milk of Magnesia is a liquid medicine that is used to relieve indigestion. Milk of Magnesia contains magnesium hydroxide, $\text{Mg(OH)}_2$. A student carries out a sequence of titrations to find the percentage by mass of magnesium hydroxide in Milk of Magnesia. Diagrams of some of the apparatus used by the student are shown.

Acid–base titrations

E150a and E155 are both brown food colourings. Devise an investigation to determine whether the brown food colouring in a soft drink is E150a or E155. Both food colourings dissolve in water. You are given solutions of E150a, E155 and the brown food colouring from the soft drink. You also have access to the apparatus usually available in a chemistry laboratory. You should include a labelled diagram with your plan and add the key practical details.

Chromatography

The setup pictured is used to carry out the electrolysis of aqueous copper(II) sulfate.

Electrolysis

Hydrogen peroxide, $\text{H}_2\text{O}_2$, reacts with iodide ions to make water and iodine, but the reaction only happens after acid has been added. $\text{H}_2\text{O}_2(aq) + 2\text{H}^+(aq) + 2\text{I}^-(aq) \rightarrow 2\text{H}_2\text{O}(l) + \text{I}_2(aq)$

Rate of reaction

Salts may be made in the laboratory by several different methods. Describe a suitable way to obtain a pure, dry sample of each named salt. In your response, include the names of any techniques, apparatus and chemicals that are used.

Preparation of salts

Mineral alstonite has two different cations, but just one anion. The table lists the tests that a student performs on a sample of alstonite. Complete the table. Name any gases that are produced.

Identification of ions and gases