Oct/Nov 2015

What process is used to prepare soluble salts?

Preparation of salts

A metal is made up of a lattice of positive ions surrounded by a ‘sea of electrons’. What occurs to the electrons and positive ions in a metal wire when an electric current passes through it?

Metallic bonding

The equation below shows aqueous sodium hydroxide being neutralised by dilute sulfuric acid. $2\text{NaOH}(aq) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{Na}_2\text{SO}_4(aq) + 2\text{H}_2\text{O}(l)$ What volume of sulfuric acid must be used to neutralise $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ NaOH?

The mole and the Avogadro constant

Which change in conditions raises the energy of the particles in a reaction?

Rate of reaction

Which one of the following changes is endothermic?

Exothermic and endothermic reactions

The enthalpy changes for the complete combustion of methane, butane and octane in oxygen are given below. methane, $\text{CH}_4$: $-890\ \text{kJ/mol}$ butane, $\text{C}_4\text{H}_{10}$: $-2877\ \text{kJ/mol}$ octane, $\text{C}_8\text{H}_{18}$: $-5512\ \text{kJ/mol}$ What are the enthalpy changes when propane and pentane are burned completely in oxygen?

Exothermic and endothermic reactions

In the ionic solid zinc phosphide, $\text{Zn}_3\text{P}_2$, what formula does the phosphide ion have?

Ion and ionic bonds

Iron is made in the blast furnace. Which statement about this process is correct?

Extraction of metals

A reaction’s energy profile diagram is shown. Which statement is correct?

Exothermic and endothermic reactions

In which reaction does nitric acid behave as an oxidising agent?

Redox

What happens during the electrolysis of dilute sulfuric acid?

Electrolysis

Which positive ions are found in aqueous copper(II) sulfate?

Ion and ionic bonds

In industry, methanol is produced by reacting carbon monoxide with hydrogen. $\text{CO(g)} + 2\text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)} \quad \Delta H = -90\ \text{kJ/mol}$ This process is normally conducted at a temperature of $400^\circ\text{C}$. Which row shows correctly how raising the temperature to above $400^\circ\text{C}$ affects both the equilibrium position and the reaction rate?

Reversible reactions and equilibrium

Which statement concerning graphite is incorrect?

Giant covalent structures

Ammonium nitrate, $\text{NH}_4\text{NO}_3$, is a synthetic fertiliser made from ammonia. What is one benefit of using ammonium nitrate as a fertiliser?

Fertilisers

The four metals and hydrogen are placed in descending order of reactivity as follows: potassium, aluminium, zinc, hydrogen, copper. Which statement about these elements is correct?

Reactivity series

Which two substances react together to produce only a salt and water?

The characteristic properties of acids and bases

An element is combusted in excess oxygen. Which statement about the oxide produced is always correct?

Oxides

Which reaction is not a neutralisation reaction?

The characteristic properties of acids and bases

From the table, which element is classed as a transition metal?

Transition elements

Three separate elements react 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

An alloy of aluminium is used in aircraft construction. Why is pure aluminium never used?

Alloys and their properties

In a titration involving an acid in the burette and an alkali, the same titration flask may need to be used again. What is the most suitable way to rinse the flask?

Acid–base titrations

What is observed when a strip of silver is placed in an aqueous solution of copper(II) sulfate?

Reactivity series

The flow chart illustrates how impure water can be treated to produce water that is safe to drink. What is not removed from the water by this process?

Water

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

Separation and purification

On oxidation, which alcohol will form $\text{CH}_3\text{CH}_2\text{CO}_2\text{H}$?

Alcohols

The diagram illustrates the structure of an organic acid. Which row is correct?

Formulae, functional groups and terminology

A carbohydrate such as starch may be represented in the way shown. What does X represent?

Polymers

P is a polymer made by condensation polymerisation. It is not a polyester, and each monomer from which it was produced contains six carbon atoms. What is the partial structure of P?

Polymers

What substances are produced in photosynthesis?

Air quality and climate

Which diagram illustrates the structure of an alloy?

Alloys and their properties

Hydrogen and nitrogen combine to produce ammonia. $\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$ Which of the following statements is correct?

Reversible reactions and equilibrium

Two containers, one containing methane and the other containing butane, are positioned at the same distance from a naked flame. The two gases are then released together. The methane reaches the flame and ignites before the butane gets there. Which statement best explains this?

Diffusion

Which statement concerning the hydrocarbon $\text{C}_2\text{H}_4$ is incorrect?

Alkenes

Metal $X$ reacts with oxygen in air. The oxide has the formula $XO$. $X$ is able to displace zinc from aqueous zinc nitrate. Which metal could $X$ be?

Reactivity series

Which of the following is a compound?

Elements, compounds and mixtures

In what way is a calcium ion, $\text{Ca}^{2+}$, produced from a calcium atom?

Ion and ionic bonds

An oxygen atom has 8 electrons, 8 protons and 10 neutrons. What is the nucleon number of this atom?

Isotopes

The structural formula of a sulfuric acid molecule is shown. How many electrons take part in forming all the covalent bonds in one molecule?

Simple molecules and covalent bonds

The diagram illustrates the fractional distillation of an aqueous solution of ethanol. Which statement accounts for why ethanol is collected as the distillate?

Separation and purification

How many moles of hydrogen atoms are present in $3.2\,\text{g}$ of methane?

The mole and the Avogadro constant

The formula for the gas ozone is $\text{O}_3$. What volume does $48\,\text{g}$ of ozone occupy at r.t.p.?

The mole and the Avogadro constant

Which substance, when mixed with pure water, will form a solution that conducts electricity?

Ion and ionic bonds

Two gases, X and Y, combine to produce a gas Z, as shown. $\text{X(g)} + 3\text{Y(g)} \rightleftharpoons 2\text{Z(g)} \quad \Delta H = -92\,\text{kJ mol}^{-1}$ Which alteration in the conditions would increase both the reaction rate and the equilibrium amount of Z?

Reversible reactions and equilibrium

When a solution of sodium carbonate was added to tap water, a white precipitate appeared. Which ion in the tap water was responsible for this precipitate forming?

Identification of ions and gases

In which reaction does nitric acid behave as an oxidising agent?

Redox

Which reaction is not a neutralisation reaction?

The characteristic properties of acids and bases

Which two substances combine to produce only a salt and water?

The characteristic properties of acids and bases

Iron is extracted in the blast furnace from the ore haematite. Which reaction occurs in the blast furnace?

Extraction of metals

Aluminium is produced from aluminium oxide by electrolysis. In this process, cryolite is used. Which statement about cryolite is correct?

Electrolysis

During a titration with an acid in the burette and an alkali, the same titration flask may have to be used again. Which rinsing procedure is the most suitable for the flask?

Acid–base titrations

An element is burned in excess oxygen. Which statement about the oxide produced is always true?

Oxides

Which of the following statements about the Periodic Table is correct?

Atomic structure and the Periodic Table

What negative ions are present in aqueous copper(II) sulfate?

Ion and ionic bonds

The reaction diagram for the Haber process is able to attain equilibrium. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ Which row indicates the gases present at equilibrium?

Reversible reactions and equilibrium

Which statement regarding graphite is incorrect?

Giant covalent structures

An energy profile diagram for a reaction is displayed. Which statement is correct?

Exothermic and endothermic reactions

The Periodic Table indicates the positions of elements A, B, C and D. These are not the usual symbols for those elements. Which element has a high melting point and can be used as a catalyst?

Transition elements

Which statement about iron and steel is incorrect?

Alloys and their properties

Several reactions are given. Which of them use a catalyst when they are carried out industrially?

Rate of reaction

Which change absorbs heat from its surroundings?

Exothermic and endothermic reactions

Which of the statements are correct?

Elements, compounds and mixtures

Which two elements form the major constituents of brass?

Alloys and their properties

Two statements about copper are given. Which of the statements are correct?

Properties of metals

What sequence shows the reactivity order of the halogens?

Group VII properties

The flow chart illustrates how contaminated water may be processed to produce water that is safe to drink. Which substance is not removed from the water by this process?

Water

Which diagram represents an isomer of butane?

Alkanes

The diagram illustrates the structure of a monomer that is used to form a polymer. What is the structure of the polymer?

Polymers

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

Separation and purification

The structures of three hydrocarbons belonging to the same homologous series are shown (W, X and Y). Which statement is correct?

Formulae, functional groups and terminology

How many of these statements about ethanol are true? 1 its molecular formula is $\text{C}_2\text{H}_6\text{O}$ 2 it is made from ethane and steam 3 it oxidises to ethanoic acid 4 it is formed by the fermentation of glucose 5 it is burned as a fuel 6 it is used to dissolve substances

Alcohols

Proteins and nylon each contain the same amide linkages. Which atom arrangement shows an amide linkage?

Formulae, functional groups and terminology

A colourless solution is stated to contain a sodium salt. Experiments were done to find out which anion is present in the solution. Test results: - dilute hydrochloric acid: no observable change - dilute nitric acid followed by aqueous silver nitrate: no precipitate formed - dilute nitric acid followed by aqueous barium nitrate: no precipitate formed Which anion might the solution contain?

Identification of ions and gases

A carbohydrate, for example starch, may be shown in the form below. What does X represent?

Polymers

Which physical changes, in each case, are exothermic?

Physical and chemical changes

The data given below could apply either to the atom or to the ion of the same element. • electronic configuration $2,8,8$ • nucleon number $40$ • proton number $20$ Which element is shown by these data?

Atomic structure and the Periodic Table

The structural formula of sulfuric acid is shown. How many electrons are used in total to form all the covalent bonds in one molecule?

Simple molecules and covalent bonds

A metal is made up of a lattice of positive ions surrounded by a ‘sea of electrons’. What happens to the electrons and positive ions in a metal wire when an electric current passes through it?

Metallic bonding

The apparatus shown has been assembled to coat a steel key with copper. The key is not being covered with copper. What change must be made to plate the key?

Electrolysis

Select your answers from the gases listed below. ammonia argon carbon dioxide chlorine ethane ethene nitrogen nitrogen(II) oxide oxygen sulfur dioxide Each gas may be used once, more than once, or not used at all.

Elements, compounds and mixtures

Methanol is made by letting carbon monoxide react with hydrogen. The forward reaction releases heat. $\text{CO(g)} + 2\text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)} \qquad \Delta H = -91\,\text{kJ mol}^{-1}$

Reversible reactions and equilibrium

Coal is a blend of carbon compounds containing a small quantity of sulfur. The sample of coal is heated without air in the apparatus shown. The distillate is a mixture made up of a colourless liquid and tar.

Carboxylic acids

An ozone layer occurs in the stratosphere around 30 km above the Earth’s surface.

Air quality and climate

Copper belongs to the metals.

Metallic bonding

A student arranged a tube as shown in the diagram. Concentrated hydrobromic acid gives off fumes of hydrogen bromide. Concentrated aqueous ammonia gives off fumes of ammonia.

Solids, liquids and gases

If 1 mole of sodium hydroxide reacts with excess hydrochloric acid, 57.1 kJ of energy is given out. $\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}$

Exothermic and endothermic reactions

The diagrams below show the structures of graphite and boron nitride.

Electrolysis

A 0.030 g sample made up of small pieces of magnesium is placed into $20\,\text{cm}^3$ of $0.10\,\text{mol dm}^{-3}$ hydrochloric acid. $\text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$

The mole and the Avogadro constant

The structure of glycolic acid is illustrated in the diagram.

Polymers

Select from the list of elements below to respond to the questions that follow. aluminium argon carbon copper iodine iron lead magnesium nitrogen oxygen sulfur Each element may be used once, more than once, or not used at all.

Atomic structure and the Periodic Table

At 200 atmospheres pressure and $200^\circ\text{C}$, phosphorus(V) chloride exists as an equilibrium mixture.

Reversible reactions and equilibrium

Plants are composed of many different kinds of carbon compounds.

Formulae, functional groups and terminology

Carbon and chlorine are used to treat water supplied for domestic use.

Water

Iron is obtained in a blast furnace.

Extraction of metals

Two students arranged the tubes as shown. Cotton wool dipped in concentrated hydrochloric acid gives off hydrogen chloride fumes. Cotton wool dipped in concentrated hydrobromic acid gives off hydrogen bromide fumes.

Diffusion

Burning 1 mole of sulfur releases 247 kJ of energy.

The mole and the Avogadro constant

The structures of diamond and silicon dioxide are displayed.

Giant covalent structures

Chlorine undergoes reaction with sodium hydroxide. $\text{Cl}_2(g) + 2\text{NaOH}(aq) \rightarrow \text{NaCl}(aq) + \text{NaClO}(aq) + \text{H}_2\text{O}(l)$

Group VII properties

When rubber is heated without any air present, a small quantity of isoprene is produced.

Polymers

Propene belongs to the alkene family. It may be prepared from a three-carbon alcohol, $\text{C}_3\text{H}_7\text{OH}$, using the apparatus shown. The reaction equation is $\text{C}_3\text{H}_7\text{OH} \rightarrow \text{C}_3\text{H}_6 + \text{H}_2\text{O}$.

Alkenes

A student uses the apparatus shown to carry out electrolysis on concentrated aqueous sodium chloride.

Electrolysis

The reactivity order for four metals $W$, $X$, $Y$ and $Z$ is given, arranged from the most reactive to the least reactive.

Reactivity series

By mass, compound $Q$ consists of $40.00\%$ carbon, $6.67\%$ hydrogen and $53.33\%$ oxygen. [$A_r$: $\text{C}$, $12$; $\text{H}$, $1$; $\text{O}$, $16$]

Formulae

No precipitate is produced when aqueous solutions of different chemicals are combined.

Ion and ionic bonds

A student uses titration to determine the percentage by mass of water in oxalic acid crystals.

Acid–base titrations

The table below summarises the tests that a student carries out on compound $Z$.

Identification of ions and gases

A student carries out an experiment to study the reaction of dilute sulfuric acid with aqueous sodium hydroxide.

Acid–base titrations

A student is finding the mass of copper in mixture A, which contains only copper and zinc. Zinc reacts with dilute sulfuric acid, whereas copper does not. Dilute sulfuric acid is added to A in the apparatus shown below. A gas is produced and collected in B.

The mole and the Avogadro constant

A student changes copper(II) oxide into copper(II) sulfate.

Preparation of salts

A learner sets up apparatus to make ethene, $\text{C}_2\text{H}_4$, as shown below.

Alkenes

A compound, T, is composed by mass of $41.0\%$ potassium, $33.7\%$ sulfur and $25.3\%$ oxygen. [$A_r$: K, $39$; S, $32$; O, $16$]

Formulae

A student places excess zinc into $50\,\text{cm}^3$ of $1.00\,\text{mol dm}^{-3}$ hydrochloric acid at $20\,^{\circ}\text{C}$. A graph, labelled G, is drawn to show how the volume of hydrogen gas produced changes with time. The experiment is carried out again under the same conditions, but this time the hydrochloric acid is at $40\,^{\circ}\text{C}$.

Rate of reaction

In which circuit below does the bulb light? (a) (b) (c) (d)

Properties of metals

Which one of the following would not react with each other to produce a precipitate? (a) aqueous sodium hydroxide and aqueous ammonium chloride (b) aqueous silver nitrate and aqueous sodium chloride (c) aqueous sodium hydroxide and aqueous iron(II) sulfate (d) aqueous barium nitrate and aqueous magnesium sulfate

Identification of ions and gases

A student is working out the percentage by mass composition of a mixture made from two solids, sodium chloride, $\text{NaCl}$, and sodium carbonate, $\text{Na}_2\text{CO}_3$. This mixture is M.

Acid–base titrations

Compound L is a solid. The table below records the tests that a student carries out on compound L.

Identification of ions and gases

A student is using the apparatus shown below to oxidise copper.

Experimental design