May/June 2015

The apparatus for fractional distillation shown below is being used to separate a mixture of two liquids. The thermometer is absent from the setup. Where should the bulb of the thermometer be positioned?

Separation and purification

When powdered calcium carbonate is added to dilute hydrochloric acid, calcium chloride, water and carbon dioxide are formed. Which ionic equation, with state symbols included, correctly represents this reaction?

The characteristic properties of acids and bases

State the relative molecular mass, $M_r$, of $\text{CuSO}_4\cdot 5\text{H}_2\text{O}$?

Relative masses of atoms and molecules

$1.00\,\text{dm}^3$ of ammonia gas is made to pass over heated copper(II) oxide. $3\text{CuO(s)} + 2\text{NH}_3\text{(g)} \rightarrow 3\text{Cu(s)} + \text{N}_2\text{(g)} + 3\text{H}_2\text{O(l)}$ At the same temperature and pressure as the ammonia, what volume of nitrogen is produced?

The mole and the Avogadro constant

When aqueous copper(II) sulfate is electrolysed with copper electrodes, what are the correct products formed at the anode (positive electrode) and the cathode (negative electrode)?

Electrolysis

Concentrated aqueous sodium chloride is electrolysed with inert electrodes. Which statement about this electrolysis is correct?

Electrolysis

The diagram illustrates the energy profile of a chemical reaction. Two energy changes are marked $X$ and $Y$. Which statement about the reaction is correct?

Exothermic and endothermic reactions

From the graph, curve 1 was produced by monitoring the decomposition of $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ hydrogen peroxide solution, catalysed by manganese(IV) oxide. $2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2$ Which change to the original experimental conditions would generate curve 2?

Rate of reaction

The equation below represents a redox reaction involving iron(II) chloride and chlorine gas. $2\text{FeCl}_2 + \text{Cl}_2 \rightarrow 2\text{FeCl}_3$ Which equation represents the reduction step in this reaction?

Redox

Identify the row that correctly describes the oxides.

Oxides

Which substance does not dissolve in water?

Elements, compounds and mixtures

The table presents the outcomes of two reactions of an aqueous solution of a salt. Adding excess aqueous sodium hydroxide produces a white precipitate. Dilute nitric acid and aqueous silver nitrate produce a yellow precipitate. Which salt is it?

Identification of ions and gases

In which of these equilibria does an increase in pressure favour the forward reaction?

Reversible reactions and equilibrium

The Contact process, the Haber process and the hydrogenation of fats each use a catalyst. Which row shows whether the catalyst used in each process is an element or a compound?

Elements, compounds and mixtures

Which chemical element is sodium?

Elements, compounds and mixtures

A non-metal element produces oxides with the formulas $\text{XO}_2$ and $\text{XO}_3$. Which element is $X$?

Oxides

The reaction between aluminium and chromium(III) oxide is shown below. $\text{aluminium} + \text{chromium(III) oxide} \rightarrow \text{chromium} + \text{aluminium oxide}$ Which statements are correct?

Extraction of metals

By referring to the Periodic Table for the relative atomic masses, which one has the smallest mass?

Relative masses of atoms and molecules

The diagram illustrates how an iron pipe beneath water can be protected from rusting. Metal $Z$ can be ...... because it is ..... reactive than iron. Which words correctly fill gaps 1 and 2?

Corrosion of metals

Brass is an alloy. Which statement about brass is true?

Alloys and their properties

Which item is manufactured from mild steel?

Uses of metals

The table gives the composition of exhaust gases from an internal combustion engine. Which gas is $Y$?

Air quality and climate

Limestone reacts with hydrochloric acid. Which reaction condition can be changed without affecting the rate of reaction?

Rate of reaction

Which two gases do not harm limestone buildings?

Air quality and climate

Iron(III) oxide may be reduced to iron by carbon. Which other element is able to reduce iron(III) oxide to iron?

Extraction of metals

An ammonium salt was mixed with excess hot aqueous sodium hydroxide, and ammonia gas was released. After ammonia was no longer being produced, aluminium was introduced into the solution left behind, and further ammonia gas was evolved. Which ammonium salt was it?

Identification of ions and gases

The molecular formula $\text{C}_3\text{H}_6\text{O}_2$ is shared by two esters. What are the names of those two esters?

Naming organic compounds

Which of these statements is correct?

Elements, compounds and mixtures

If one mole of a compound, $X$, is cracked, it gives one mole of propene and one mole of hydrogen. $X \rightarrow \text{C}_3\text{H}_6 + \text{H}_2$. What type of compound is $X$?

Alkanes

Which option gives the correct definition of isomers?

Formulae, functional groups and terminology

Which of the following has not been produced by reacting a carboxylic acid with an alcohol?

Carboxylic acids

Which among these polymers is a protein?

Polymers

For the addition polymer poly(propene), what is the lowest whole-number ratio of carbon atoms to hydrogen atoms?

Polymers

A particle has 34 protons, 45 neutrons and 36 electrons. Which symbol correctly represents this particle?

Atomic structure and the Periodic Table

Which of the following statements about vegetable oil and the margarine produced from it is correct?

Alkenes

Which molecule has three pairs of electrons shared between two of its atoms?

Simple molecules and covalent bonds

What is observed when sodium chloride melts?

Ion and ionic bonds

Which compound has exactly eight covalent bonds?

Simple molecules and covalent bonds

Which substance shows metallic bonding?

Metallic bonding

A gas cylinder is positioned in each corner of a square-shaped room. Each cylinder holds a different gas at the same pressure. The gases are let out at the same instant. Which gas will arrive at the centre of the room first?

Diffusion

The apparatus for fractional distillation shown is being used to separate a mixture of two liquids. One thermometer is not included in the apparatus. At what position should the bulb of the thermometer be placed?

Separation and purification

By using the relative atomic masses from the Periodic Table, which one has the largest mass?

Relative masses of atoms and molecules

Nitrogen and hydrogen are reacted to form ammonia in the Haber process. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ Calculate the percentage yield when $60\,\text{kg}$ of ammonia is obtained from $60\,\text{kg}$ of hydrogen?

The mole and the Avogadro constant

Determine the relative molecular mass, $M_r$, of $\text{CuSO}_4\cdot5\text{H}_2\text{O}$?

Relative masses of atoms and molecules

The list gives some substances that conduct electricity. 1 aqueous sodium chloride 2 copper 3 graphite In which substance(s) are electrons the only charge carriers in conduction?

Metallic bonding

Caesium belongs to Group I metals. Which reaction involving this element would fail to produce hydrogen?

Group I properties

The energy profile shows a chemical reaction taking place both in the presence of a catalyst and in its absence. What is the enthalpy change for the catalysed reaction?

Exothermic and endothermic reactions

Hydrogen combines with iodine to produce hydrogen iodide. The reaction occurs slowly. $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g)$ 1 mole of hydrogen gas and 1 mole of iodine vapour were brought together and left to react. After $t$ seconds, $0.6$ moles of hydrogen were still present. What is the number of moles of iodine left after $t$ seconds?

The mole and the Avogadro constant

Acidified potassium manganate(VII) is used as the test reagent. When this is added to an aqueous solution of compound X, the colour of the test reagent changes from .....1..... . This colour change indicates that X is .....2..... . Which words correctly fill blanks 1 and 2?

Alkenes

You are given dilute hydrochloric acid, together with • solid copper, • solid magnesium, • lead nitrate in aqueous solution, • silver nitrate in aqueous solution. How many different insoluble chlorides could you prepare?

Preparation of salts

On the graph, curve 1 was produced by monitoring the decomposition of $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ hydrogen peroxide solution, with manganese(IV) oxide as the catalyst. $2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2$ Which change to the initial experimental conditions would give curve 2?

Rate of reaction

The concentration of aqueous sodium carbonate can be determined by allowing it to react with hydrochloric acid of known concentration, using methyl orange as the indicator. Which pieces of apparatus are required?

Acid–base titrations

A colourless solution reacts with magnesium, producing a salt and hydrogen gas. What role is this solution playing?

The characteristic properties of acids and bases

This equation represents a redox reaction between iron(II) chloride and chlorine gas. $2\text{FeCl}_2 + \text{Cl}_2 \rightarrow 2\text{FeCl}_3$ Which equation represents the reduction process in this reaction?

Redox

Which compound yields the largest number of ions when 1 mole is dissolved in water?

Ion and ionic bonds

The equation for the reaction that occurs during ammonia manufacture is shown. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ $\Delta H = -92\,\text{kJ mol}^{-1}$ The reaction is performed at about $200$ atmospheres pressure, with an iron catalyst, and at temperatures from $350\,^{\circ}\text{C}$ to $450\,^{\circ}\text{C}$. Which statement is incorrect?

Reversible reactions and equilibrium

To which element does sodium belong?

Atomic structure and the Periodic Table

Based on their positions in the Periodic Table, what common property would you predict for the elements titanium, vanadium, chromium and cobalt?

Transition elements

Which two gases do not harm limestone buildings?

Air quality and climate

The facts below are known about four metals, P, Q, R and S. What is the correct reactivity order, with the most reactive first?

Reactivity series

Which metal must be obtained from its ore by electrolysis?

Extraction of metals

Aluminium is made by the electrolysis of molten aluminium oxide. Which statement correctly describes the process?

Electrolysis

Which molecules contain at least one double covalent bond?

Simple molecules and covalent bonds

Hydrides are compounds made up of an element and hydrogen only. Which statement is incorrect?

Arrangement of elements

During the extraction of iron from its ore in the blast furnace, limestone is added. What is the purpose of the limestone?

Extraction of metals

Two separate pieces of iron are shown in water, with zinc attached to one and copper attached to the other, as illustrated. Which of the following statements are correct?

Corrosion of metals

A diagram shows a biogas generator. If the gas is collected, it may be burned as a fuel. However, if the gas is released, it acts as an atmospheric pollutant. What gas is it?

Fuels

Which of the following statements about alkanes is correct?

Alkanes

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

Alcohols

If one mole of the compound, $X$, is cracked, it gives one mole of propene and one mole of hydrogen. $X \rightarrow \text{C}_3\text{H}_6 + \text{H}_2$ What class of compound is $X$?

Alkanes

The diagram illustrates part of the structure of a polymer. Which pair of reagents might have been used to make this polymer?

Polymers

Which of the following is not produced by reacting a carboxylic acid with an alcohol?

Carboxylic acids

Which statement concerning the properties of the four alkanes from methane through butane is incorrect?

Alkanes

Cr, Co, Fe and Mn are all transition elements. Which particles contain the same number of electrons?

Atomic structure and the Periodic Table

Which one of these polymers is a protein?

Polymers

Which substance contains metallic bonding?

Metallic bonding

Which compound has exactly eight covalent bonds?

Simple molecules and covalent bonds

The table presents the outcomes of two reactions involving an aqueous solution of a salt. What might the salt be?

Identification of ions and gases

Which row gives the correct statements about how quickly a gas diffuses?

Diffusion

What occurs when sodium chloride is melted?

Ion and ionic bonds

Use any of the organic compounds listed below to answer the questions that follow. butane butanoic acid butyl ethanoate ethanol ethyl butanoate methane methanol methyl propanoate propane propanoic acid propanol Each compound may be used once, more than once, or not used at all.

Formulae, functional groups and terminology

Farmers make use of some calcium compounds.

Fertilisers

Ozone molecules are constantly broken apart and rebuilt in the upper atmosphere.

Reversible reactions and equilibrium

The sulfur isotopes are $^{32}_{16}\text{S}$ and $^{33}_{16}\text{S}$.

Simple molecules and covalent bonds

The flow chart displays several reactions involving copper(II) nitrate, $\text{Cu(NO}_3)_2$.

Preparation of salts

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

Preparation of salts

Molybdenum is a transition element. It is used to produce steel that is very hard. Molybdenum can be manufactured by heating molybdenum(VI) oxide, $\text{MoO}_3$, together with aluminium.

Extraction of metals

Large quantities of poly(chloroethene) are made every year. The flow chart illustrates the stages involved in the manufacture of poly(chloroethene).

Polymers

Alkanes form a homologous series of saturated hydrocarbons. The table gives information about several alkanes.

Alkanes

Use the compounds listed below to answer the questions on the opposite page. Each compound may be used once, more than once, or not at all. The compounds are labelled A, B, C, D, E, F, G and H, and their displayed formulae are shown.

Formulae, functional groups and terminology

Hydrogen combines with halogens to make hydrogen halides.

Reversible reactions and equilibrium

The phosphorus isotopes shown are $^{31}_{15}\text{P}$ and $^{32}_{15}\text{P}$.

Simple molecules and covalent bonds

The diagram outlines several reactions of iron(II) sulfate, FeSO$_4$.

Identification of ions and gases

Electrolysis is frequently used for extracting and purifying elements.

Electrolysis

Ammonium carbonate, $(\text{NH}_4)_2\text{CO}_3$, is a white solid used in ‘smelling salts’. When it is heated, it breaks down. $(\text{NH}_4)_2\text{CO}_3(s) \rightarrow 2\text{NH}_3(g) + \text{H}_2\text{O}(g) + \text{CO}_2(g)$.

Preparation of salts

Titanium can be produced by heating titanium(IV) chloride, $\text{TiCl}_4$, together with magnesium.

Redox

The flow chart displays the stages used to manufacture poly(propenenitrile).

Polymers

Alkenes form a homologous series of unsaturated hydrocarbons. The table gives information about some alkenes.

Alkenes

Describe the visible appearance of zinc.

Preparation of salts

Use the thermometer readings to fill the table for ammonium chloride.

Experimental design

The general expression for a carboxylic acid is $\text{C}_n\text{H}_{2n+1}\text{COOH}$. G is a carboxylic acid with relative formula mass $88$.

Formulae, functional groups and terminology

For questions $3$ to $7$ inclusive, put a tick (✓) in the box beside the right answer.

Experimental design

When concentrated aqueous sodium chloride is electrolysed with carbon electrodes, which statement is correct?

Electrolysis

Metal $A$ pushes metal $B$ out of a solution containing its ions. Metal $B$ pushes metal $C$ out of a solution containing its ions. What might $A$, $B$ and $C$ be?

Reactivity series

A student places solid zinc powder into a beaker of aqueous copper(II) sulfate. Which of the following observations are correct?

Reactivity series

A student needs to prepare $250\,\text{cm}^3$ of $0.20\,\text{mol dm}^{-3}$ sodium hydroxide. [$A_r$: Na, $23$; O, $16$; H, $1$] State the mass of sodium hydroxide needed.

The mole and the Avogadro constant

Ammonium sulfate is a nitrogenous fertiliser. The nitrogen it contains helps plants to grow.

Acid–base titrations

The table below lists the tests carried out on compound $M$ by a student and the conclusions drawn from the observations.

Identification of ions and gases

A student places a small strip of magnesium ribbon in a crucible and heats it for several minutes. Magnesium oxide is formed.

The characteristic properties of acids and bases

A learner uses the setup shown to explore how marble $(\text{CaCO}_3)$ reacts with hydrochloric acid.

Rate of reaction

A student uses the apparatus shown to determine the energy released by the combustion of each of three alcohols, X, Y and Z. In every experiment $0.1\text{ mol}$ of alcohol is burnt, and the water starts at $20\,^{\circ}\text{C}$.

Alcohols

For questions 3 to 7 inclusive, put a tick $(\checkmark)$ in the box next to the correct answer.

Experimental design

Water with a small amount of dilute sulfuric acid is electrolysed with carbon electrodes.

Electrolysis

The diagrams show four tubes. In each tube, a piece of metal is placed in an aqueous solution containing ions of one of the other two metals.

Reactivity series

A small piece of sodium is put on the surface of water. It reacts, and a solution forms.

Group I properties

Calcium hydroxide reacts with hydrochloric acid in the equation below: $\text{Ca(OH)}_2 + 2\text{HCl} \rightarrow \text{CaCl}_2 + 2\text{H}_2\text{O}$.

The mole and the Avogadro constant

‘Lawn sand’ consists of sand combined with iron(II) sulfate and ammonium sulfate, and it is used to encourage grass growth.

Acid–base titrations

The table summarises the tests a student carries out on compound $V$.

Identification of ions and gases