Oct/Nov 2021

A mass spectrum for a neon sample is shown. The relative abundance of each peak is given in brackets above it. Determine the relative atomic mass, $A_r$, of this neon sample.

Atoms, molecules and stoichiometry

The equation indicates that $\text{H}_2(g)$ and $\text{I}_2(g)$ combine to produce an equilibrium mixture. $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g) \quad \Delta H^\circ = -9.6\ \text{kJ mol}^{-1}$. An equal amount of $\text{H}_2(g)$ and $\text{I}_2(g)$ is prepared at temperature $T_1$, and the mixture’s composition is tracked. The outcome is displayed as a graph. The test is carried out again at a lower temperature, $T_2$. Which different graph would be obtained?

Equilibria

The diagram illustrates the Boltzmann distribution of energies for a reactant gas. For a particular reaction, the activation energy is $X$. Which alteration to the diagram happens if an effective catalyst is added at the same temperature?

Reaction kinetics

For the complete combustion of 1 mol of its atoms, which element uses the fewest moles of oxygen?

Atoms, molecules and stoichiometry

An element, $Y$, undergoes the following reactions. $Y$ burns in $\text{O}_2$ to give a white solid, and this solid reacts with $\text{HCl(aq)}$ to produce a solution. When $\text{NaOH(aq)}$ is added, a white precipitate is formed, and this precipitate dissolves in excess $\text{NaOH(aq)}$ to make a solution. Which element could $Y$ be?

The Periodic Table: chemical periodicity

Which list contains three compounds that are all soluble in water?

Group 2

When anhydrous magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it breaks down to form a white solid and a mixture of two gases, $X$ and $Y$. $Y$ is oxygen. What is the ratio $\dfrac{\text{mass of } X \text{ released}}{\text{mass of } Y \text{ released}}$?

Atoms, molecules and stoichiometry

In nine separate experiments, a halogen reactivity test is carried out by adding an aqueous solution of each halogen to the same volume of an aqueous solution that contains halide ions, as shown in the table. Each of the nine mixtures is then shaken on its own with the same volume of hexane. The tubes are then allowed to stand so that the aqueous layer and the organic layer form separate layers. How many test-tubes have a purple upper hexane layer?

Group 17

$Z$ is a compound made from sodium, chlorine and oxygen. It has $45.1\%$ oxygen by mass. $Z$ is made by reacting sodium hydroxide with chlorine. Which row gives the reaction conditions and the oxidation state of chlorine in $Z$?

Group 17

Which line is correct?

The Periodic Table: chemical periodicity

The table shows two possible environmental effects of adding excessive ammonium nitrate fertiliser to the soil. Which row is correct?

Nitrogen and sulfur

2.0 g of ammonium nitrate, $\text{NH}_4\text{NO}_3$, breaks down to produce 0.90 g of water and one gas. What is the identity of the gas?

Atoms, molecules and stoichiometry

Hex-2-ene can be produced in the reaction illustrated below. Which statement correctly describes this reaction?

Hydrocarbons

Only structural isomerism should be taken into account for this question. Molecule $X$ has three C=C double bonds. One mole of $X$ is reacted with three moles of HBr. The carbon skeleton remains unchanged. How many distinct products are produced?

Hydrocarbons

When answering this question, you should take structural isomerism and stereoisomerism into account. A colourless liquid, $\text{C}_5\text{H}_{11}\text{Cl}$, is present as a mixture of two optical isomers. On heating with sodium hydroxide in ethanol, only a mixture of two alkenes is produced. What might the colourless liquid be?

Halogen compounds

When 2-bromo-2-methylpropane reacts with aqueous sodium hydroxide, an alcohol is produced. Which diagram shows the first step in the reaction mechanism?

Halogen compounds

If an organic compound, Q, is reacted with phosphorus pentachloride, fumes of hydrogen chloride are released. When Q is heated with acidified aqueous potassium dichromate(VI), the solution changes to green. What is Q?

Hydroxy compounds

Alcohol Y forms a yellow precipitate with alkaline aqueous iodine. It may be oxidised to produce a mixture of products, one of which is substance Z. Substance Z produces a red-brown precipitate with Fehling’s solution. Which alcohol might Y be?

Hydroxy compounds

$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide to produce an organic compound known as a cyanohydrin. Which statement is correct?

Carbonyl compounds

When compound R is reduced with $\text{LiAlH}_4$, the product obtained is 4-methylpentane-2,3-diol. What might compound R be?

Carbonyl compounds

Citric acid occurs in lemon juice. citric acid $\text{HO}_2\text{CCH}_2\text{C(OH)(CO}_2\text{H)CH}_2\text{CO}_2\text{H}$ What volume of $0.40\ \text{mol dm}^{-3}$ sodium hydroxide solution is needed to neutralise a solution that contains $0.0050\ \text{mol}$ of citric acid?

Atoms, molecules and stoichiometry

The structural formula for an ester is $\text{(CH}_3)_2\text{CHOCO(CH}_2)_2\text{CH}_3$. This ester is heated under reflux with aqueous hydrochloric acid. Which two products are produced?

Carboxylic acids and derivatives

Which element in this list has the greatest fifth ionisation energy?

The Periodic Table: chemical periodicity

Infra-red spectra for three organic compounds are displayed. What might the three compounds be?

Chemical bonding

Which changes can be used to determine the rates of chemical reactions?

Reaction kinetics

Iron reacts with steam to form hydrogen and an iron oxide. $3\text{Fe(s)} + 4\text{H}_2\text{O(g)} \rightleftharpoons \text{Fe}_3\text{O}_4\text{(s)} + 4\text{H}_2\text{(g)}$ All four substances are present in a system at equilibrium. Which changes would reduce the mass of Fe present at equilibrium?

Equilibria

Ethylene glycol, $\text{HOCH}_2\text{CH}_2\text{OH}$, is employed as a de-icer. It makes it possible for ice to melt at temperatures lower than $0^\circ\text{C}$. Which of the following statements are correct?

States of matter

Which molecules have at least one unpaired electron?

Chemical bonding

Which elements combine to produce a chloride in which both covalent bonding and coordinate (dative covalent) bonding are present?

Chemical bonding

Which of the following statements about calcium oxide are correct?

Group 2

A diketo acid is a compound that contains two ketone groups and one carboxylic acid group. The structures of limonene and terpinolene are shown. Which statements about how limonene and terpinolene react are correct?

Chemical bonding

A single molecule of dodecane, $\text{C}_{12}\text{H}_{26}$, undergoes cracking to give three product molecules, X, Y and Z. X is an alkane with a straight chain. Y and Z are straight-chain alkenes that have different $M_r$ values. Which of the following statements about X, Y and Z are correct?

Hydrocarbons

Which of the following statements about chlorofluoroalkanes are correct?

Halogen compounds

Ion $X^{2+}$ possesses the same electronic configuration as the atom Kr. What electronic configuration does an atom of $X$ have?

Atomic structure

In which reactions is water one of the products of propan-1-ol?

Hydroxy compounds

What kind of interaction occurs between water molecules and metal cations in aqueous solution?

Chemical bonding

Under room conditions, which substance departs most from the behaviour expected of an ideal gas?

States of matter

To find the enthalpy of neutralisation for a strong acid and a strong alkali, $25.0\ \text{cm}^3$ of $2.00\ \text{mol dm}^{-3}$ sodium hydroxide is mixed with $25.0\ \text{cm}^3$ of $2.00\ \text{mol dm}^{-3}$ hydrochloric acid, giving a temperature rise of $12^\circ\text{C}$. A second experiment follows the same procedure, except that $50.0\ \text{cm}^3$ of $2.00\ \text{mol dm}^{-3}$ sodium hydroxide is added to $50.0\ \text{cm}^3$ of $2.00\ \text{mol dm}^{-3}$ hydrochloric acid. How much does the temperature increase in the second experiment?

Chemical energetics

Which equation illustrates the enthalpy change of atomisation for iodine?

Chemical energetics

Zinc atoms may be oxidised into $\text{Zn}^{2+}$ ions by dichromate(VI) ions in an acidic solution. In this reaction, chromium is reduced to $\text{Cr}^{3+}$. Which equation is correct?

Electrochemistry

A sample of compound X is made up of $40.0\%$ carbon, $6.7\%$ hydrogen and $53.3\%$ oxygen by mass. What is the empirical formula for compound X?

Atoms, molecules and stoichiometry

Inside a car’s exhaust system, in a catalytic converter, carbon monoxide is oxidised to carbon dioxide, while nitrogen monoxide is reduced to nitrogen. What are the oxidation number changes for carbon and nitrogen in these two reactions?

Electrochemistry

NO and NO$_2$ are each found in the lower atmosphere as pollutants. The reaction sequence below shows how ozone is formed from oxygen in the lower atmosphere. This sequence happens repeatedly many times. $\text{NO}_2(g) \rightarrow \text{NO}(g) + \text{O}(g)$ $\text{NO}(g) + \tfrac{1}{2}\text{O}_2(g) \rightarrow \text{NO}_2(g)$ $\text{O}_2(g) + \text{O}(g) \rightarrow \text{O}_3(g)$ Which statement about this reaction sequence is correct?

Reaction kinetics

A combination of two Period 3 oxides is placed in water. A solution is produced and its pH is slightly below $7$. Which oxides might be present in the mixture?

Equilibria

Which of these statements about compounds of the Group 2 metals is correct?

Chemical bonding

A $0.005$ mol portion of anhydrous calcium carbonate is fully thermally decomposed, producing $100\ \text{cm}^3$ of gas. In a separate experiment, a $0.005$ mol portion of anhydrous calcium nitrate is also fully thermally decomposed under the same conditions. The volume of the gaseous products is then measured. What is the total volume of gaseous products obtained from the calcium nitrate?

Atoms, molecules and stoichiometry

Redox reactions occur frequently in the chemistry of Group 17 elements. Which statement is correct?

Electrochemistry

Silver chloride and silver iodide establish equilibria when they are placed in water. $\text{AgCl}(s) \rightleftharpoons \text{Ag}^+(aq) + \text{Cl}^-(aq)\qquad K_c = K_1$ $\text{AgI}(s) \rightleftharpoons \text{Ag}^+(aq) + \text{I}^-(aq)\qquad K_c = K_2$ For each case, the equilibrium position is far to the left. Silver iodide does not dissolve in aqueous ammonia. Silver chloride does dissolve in aqueous ammonia. A further equilibrium is established. $\text{Ag}^+(aq) + 2\text{NH}_3(aq) \rightleftharpoons \text{Ag(NH}_3)_2^+(aq)\qquad K_c = K_3$ This equilibrium lies to the right. What is the order of magnitude of these three equilibrium constants?

Equilibria

X is the ion of a metal that burns with a red flame. Y is an ion which, when it reacts with concentrated $\text{H}_2\text{SO}_4$, produces $\text{H}_2\text{S}$. What might the formula of a compound containing X and Y be?

Nitrogen and sulfur

Oxides of nitrogen occur in the environment because of both natural and human-made sources. Which row is correct?

Nitrogen and sulfur

Magnesium hydroxide is soluble in aqueous ammonium chloride, but it is insoluble in aqueous sodium chloride. Which statement accounts for this observation?

Equilibria

Which of these statements is correct?

Atoms, molecules and stoichiometry

The formula for hydrocortisone acetate is displayed. Which row is the correct one?

Atoms, molecules and stoichiometry

Bromomethane, $\text{CH}_3\text{Br}$, breaks down in the stratosphere to produce methyl free radicals and bromine free radicals. Which row gives the correct description of this decomposition?

Chemical bonding

Both structural isomerism and stereoisomerism must be considered when you answer this question. $Y$ is a hydrocarbon in the gaseous state that decolourises aqueous bromine. It has no ring structures. Under room conditions, $10.0\,\text{g}$ of $Y$ occupies a volume of $3.43\,\text{dm}^3$. How many different isomeric structures can $Y$ have?

Hydrocarbons

Which equation shows a correct propagation step in the chlorination of ethane?

Reaction kinetics

Butanoic acid may be prepared from $1$-bromopropane in two steps. stage $1$ $\text{CH}_3\text{CH}_2\text{CH}_2\text{Br} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CN}$ stage $2$ $\text{CH}_3\text{CH}_2\text{CH}_2\text{CN} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CO}_2\text{H}$ What are the reaction types for stage $1$ and stage $2$?

Organic synthesis

A halogenoalkane has the molecular formula $\text{C}_5\text{H}_{11}\text{Br}$. When this halogenoalkane is warmed with ethanolic sodium hydroxide, no alkene is produced. Which halogenoalkane could this be?

Halogen compounds

Compound $P$ is refluxed with excess acidified potassium dichromate(VI) to produce compound $Q$. The boiling point of compound $Q$ is lower than that of compound $P$. What could be compound $P$?

Hydroxy compounds

When answering this question, you should take structural and stereoisomerism into account. An organic compound, $X$, is dehydrated by heating with concentrated phosphoric(V) acid. Only two organic products are produced. What substance could $X$ be?

Hydroxy compounds

Which compound gives a precipitate when tested with $2,4$-dinitrophenylhydrazine reagent and also when tested with alkaline aqueous iodine?

Carbonyl compounds

Organic compound $Z$ contains both an alcohol functional group and a carboxylic acid functional group. When compound $Z$ reacts with magnesium carbonate, it forms a salt with a relative formula mass of $230.3$. Compound $Z$ shows no reaction with acidified potassium manganate(VII). What might compound $Z$ be?

Hydroxy compounds

Technetium ($\text{Tc}$) is a second row transition element that is not found naturally on Earth. One isotope of it contains $56$ neutrons. What nucleon number does this isotope have?

Chemistry of transition elements

The infra-red spectrum for $Y$ is presented. What might $Y$ be?

Chemical bonding

The Boltzmann distribution diagram represents a set quantity of a gas at two temperatures, $T_1$ and $T_2$. Which of the following statements correctly describe features of the diagram?

Chemical energetics

Four solutions, each with concentration $0.1\,\text{mol dm}^{-3}$, were examined using a pH meter. The outcomes are shown: acid 1: $\text{CH}_3\text{CO}_2\text{H}$, pH $4$ acid 2: $\text{HNO}_3$, pH $1$ base 1: $\text{CH}_3\text{NH}_2$, pH $11$ base 2: $\text{NaOH}$, pH $14$ Which statements account for these results?

Equilibria

Identify which reactions are redox reactions.

Electrochemistry

On heating the liquid $\text{N}_2\text{F}_4$, it breaks down to give one product only, X. Which of these statements are correct?

Equilibria

The statements below compare certain properties of the oxides and chlorides of sodium and silicon. Which statements are correct?

Chemical bonding

Which of the following statements concerning ammonium chloride are correct?

Nitrogen compounds

What feature is the same for a pair of optical isomers?

Chemical bonding

Which molecular formulae can correspond to at least one compound that is able to undergo addition polymerisation?

Polymerisation

Which of the reactions produce products that contain a chiral centre?

Chemical bonding

Which atom contains more unpaired electrons than paired electrons in orbitals with principal quantum number $2$?

Atomic structure

Ethyl butanoate is heated with a dilute aqueous sodium hydroxide solution. Which substances are formed in this reaction?

Carboxylic acids and derivatives

Atom X is the central atom in a molecule. In this molecule, atom X has four pairs of valence electrons in its outer shell. These four pairs of valence electrons include at least one bond pair and at least one lone pair. What might be a possible shape of the molecule?

Chemical bonding

Which molecule has the greatest total dipole?

Chemical bonding

As the electronegativity of the atom bonded to hydrogen increases, the strength of hydrogen bonding also increases. Information on a range of hydrides is provided. Which statement together with its reason about these hydrides is correct?

Chemical bonding

The general gas equation may be applied to calculate the $M_r$ of a gas. For a gas sample with a mass of $m$ grams, which expression gives the value of $M_r$?

States of matter

The equation describing the formation of ammonium chloride is given below. $\text{NH}_3(g) + \text{HCl}(g) \rightleftharpoons \text{NH}_4\text{Cl}(s) \quad \Delta H = -314\,\text{kJ mol}^{-1}$. Which diagram represents the correctly labelled reaction pathway diagram for the decomposition of ammonium chloride?

Chemical energetics

A mass spectrum for a neon sample is displayed. The relative abundance of each peak is given in brackets above the peak. What is the relative atomic mass, $A_r$, of this neon sample?

Atomic structure

The equation indicates that $\text{H}_2(g)$ and $\text{I}_2(g)$ combine to establish an equilibrium mixture. $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g)\qquad \Delta H^{\circ} = -9.6\,\text{kJ mol}^{-1}$ An equal-amount mixture of $\text{H}_2(g)$ and $\text{I}_2(g)$ is prepared at temperature $T_1$, and the mixture’s composition is followed. The outcome is shown on a graph. The experiment is carried out again at a lower temperature, $T_2$. Which new graph would be obtained?

Equilibria

The diagram illustrates the Boltzmann distribution of energies for a reactant gas. For a certain reaction, the activation energy is $X$. What change would be seen on the diagram if an effective catalyst were added at the same temperature?

Reaction kinetics

Which element needs the smallest number of moles of oxygen to achieve the complete combustion of $1\ \text{mol}$ of its atoms?

Atoms, molecules and stoichiometry

An element, $Y$, takes part in the sequence shown below. When $Y$ burns in $\text{O}_2$, a white solid is formed. This white solid reacts with $\text{HCl(aq)}$ to produce a solution. When $\text{NaOH(aq)}$ is added, a white precipitate is formed, and this precipitate then dissolves in excess $\text{NaOH(aq)}$ to form a solution. Which element could $Y$ be?

The Periodic Table: chemical periodicity

In which list are all three compounds able to dissolve in water?

States of matter

When anhydrous magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it breaks down to form a white solid and a mixture of two gases, $X$ and $Y$. $Y$ is oxygen. What is the ratio $\dfrac{\text{mass of } X \text{ released}}{\text{mass of } Y \text{ released}}$?

Atoms, molecules and stoichiometry

Across nine experiments designed to test the reactivity of the halogens, an aqueous solution of each halogen is mixed with the same volume of an aqueous solution containing halide ions, as shown in the table. Each of the nine mixtures is then shaken separately with the same volume of hexane. The nine tubes are left until the aqueous and organic solvents form separate layers. How many test-tubes have a purple top hexane layer?

Electrochemistry

$Z$ is a compound made from sodium, chlorine and oxygen. It has $45.1\%$ oxygen by mass. $Z$ is made by reacting sodium hydroxide with chlorine. Which row gives the reaction conditions and the oxidation state of chlorine in $Z$?

Group 17

Which row is the correct one?

The Periodic Table: chemical periodicity

The table shows two possible environmental effects of applying too much ammonium nitrate fertiliser to the soil. Which row is correct?

Nitrogen and sulfur

$2.0\,\text{g}$ of ammonium nitrate, $\text{NH}_4\text{NO}_3$, breaks down to produce $0.90\,\text{g}$ of water and one gas. Which gas is this?

Atoms, molecules and stoichiometry

Hex-2-ene may be produced by the reaction illustrated. Which statement about this reaction is correct?

Hydrocarbons

When answering this question, consider only structural isomerism. Molecule $X$ has three $\text{C=C}$ double bonds. One mole of $X$ reacts with three moles of $\text{HBr}$. The carbon skeleton remains unchanged. How many distinct products are produced?

Halogen compounds

Both structural isomerism and stereoisomerism ought to be taken into account when answering this question. A colourless liquid, $\text{C}_5\text{H}_{11}\text{Cl}$, occurs as a mixture of two optical isomers. When it is heated with sodium hydroxide in ethanol, only a mixture of two alkenes is produced. What could the colourless liquid be?

Halogen compounds

An alcohol is produced when 2-bromo-2-methylpropane reacts with aqueous sodium hydroxide. Which diagram shows the first stage of the reaction mechanism?

Halogen compounds

If an organic compound, Q, is reacted with phosphorus pentachloride, hydrogen chloride fumes are given off. If Q is then heated with acidified aqueous potassium dichromate(VI), the solution changes to green. What is Q?

Hydroxy compounds

When alcohol Y is added to alkaline aqueous iodine, a yellow precipitate is produced. If Y is oxidised, it forms a mixture of products, one of which is substance Z. Substance Z produces a red-brown precipitate with Fehling’s solution. Which alcohol is a possible identity for Y?

Hydroxy compounds

$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ undergoes reaction with hydrogen cyanide to produce an organic product known as a cyanohydrin. Which of the following statements is correct?

Carbonyl compounds

If compound R is reduced using $\text{LiAlH}_4$, the product formed is 4-methylpentane-2,3-diol. What might compound R be?

Carbonyl compounds

Citric acid occurs in lemon juice. Citric acid: $\text{HO}_2\text{CCH}_2\text{C(OH)(CO}_2\text{H)CH}_2\text{CO}_2\text{H}$ What volume of $0.40\ \text{mol dm}^{-3}$ sodium hydroxide solution is needed to neutralise a solution that contains $0.0050$ mol of citric acid?

Atoms, molecules and stoichiometry

An ester has the structural formula $(\text{CH}_3)_2\text{CHOCO(CH}_2)_2\text{CH}_3$. This ester is heated under reflux with aqueous hydrochloric acid. Which two products are produced?

Equilibria

Which one of these elements has the greatest fifth ionisation energy?

The Periodic Table: chemical periodicity

The infra-red spectra for three organic compounds are shown. Which three compounds could these be?

Chemical bonding

Which changes may be used to determine the rates of chemical reactions?

Reaction kinetics

Iron reacts with steam to form hydrogen and an oxide of iron. $3\text{Fe(s)} + 4\text{H}_2\text{O(g)} \rightleftharpoons \text{Fe}_3\text{O}_4\text{(s)} + 4\text{H}_2\text{(g)}$ A mixture containing all four substances has reached equilibrium. Which changes would reduce the amount of Fe present at equilibrium?

Equilibria

Ethylene glycol, $\text{HOCH}_2\text{CH}_2\text{OH}$, is used as a de-icer. It enables ice to melt at temperatures below $0\,^{\circ}\text{C}$. Which statements are correct?

States of matter

Which of these molecules has at least one unpaired electron?

Chemical bonding

Which element forms a chloride in which both covalent bonding and coordinate (dative covalent) bonding occur?

Chemical bonding

Which of the following statements about calcium oxide are correct?

Chemical bonding

A diketo acid is a compound that contains two ketone groups and one carboxylic acid group. The structures of limonene and terpinolene are displayed. Which statements concerning the reactions of limonene and terpinolene are correct?

Hydrocarbons

A single molecule of dodecane, $\text{C}_{12}\text{H}_{26}$, is cracked to give three product molecules, X, Y and Z. X is a straight-chain alkane. Y and Z are straight-chain alkenes with different $M_r$ values. Which statements concerning X, Y and Z are correct?

Atoms, molecules and stoichiometry

Which statements about chlorofluoroalkanes are correct?

Halogen compounds

The ion $X^{2+}$ is electronically arranged in the same way as the atom Kr. What electronic configuration does an atom of $X$ have?

Atomic structure

In which of these reactions does water appear as one of the products of propan-1-ol?

Hydroxy compounds

What type of interaction is present between water molecules and metal cations in aqueous solution?

Chemical bonding

Which substance displays the greatest departure from the properties of an ideal gas under room conditions?

States of matter

To determine the enthalpy of neutralisation for a strong acid and a strong alkali, $25.0\,\text{cm}^3$ of $2.00\,\text{mol dm}^{-3}$ sodium hydroxide is mixed with $25.0\,\text{cm}^3$ of $2.00\,\text{mol dm}^{-3}$ hydrochloric acid. The temperature rises by $12\,^{\circ}\text{C}$. For a second trial, the same procedure is followed, except that $50.0\,\text{cm}^3$ of $2.00\,\text{mol dm}^{-3}$ sodium hydroxide is mixed with $50.0\,\text{cm}^3$ of $2.00\,\text{mol dm}^{-3}$ hydrochloric acid. What temperature increase is observed in the second trial?

Chemical energetics

Which equation shows the enthalpy change of atomisation for iodine?

Chemical energetics

Zinc atoms are able to be oxidised to $\text{Zn}^{2+}$ ions by dichromate(VI) ions in acidic solution. In this reaction, chromium is reduced to $\text{Cr}^{3+}$. Which equation is correct?

Electrochemistry