O Level Chemistry 5070 Paper 12, Oct/Nov 2023

A solid substance is placed in a flask. The flask is gently heated and the temperature of the substance is recorded at regular time intervals. The diagram shows a graph of temperature against time for this experiment. At which point does the flask contain both a solid and a liquid? A B C D

A crystal of sodium chloride is dropped into a beaker of water and the crystal dissolves. There are four stages in this process. 1 The water molecules collide with the ions in the crystal lattice. 2 The ionic bonds in the crystal break. 3 The ions move randomly in all directions until they are evenly spread throughout the solution. 4 The ions continue to move randomly in all directions but remain evenly spread throughout the solution. At which stages is diffusion occurring? A 1, 2 and 4 B 2 and 3 C 3 only D 4 only

W is ethene, X is air, Y is iodine and Z is brass. Which row is correct?

Which statement about the isotopes of bromine is correct? A They are atoms with the same number of electrons and a different number of protons. B They are atoms with the same number of neutrons and the same number of electrons. C They are atoms with the same number of protons and the same chemical properties. D They are atoms with the same number of protons and the same physical properties.

Which diagram shows a section of the ionic lattice of sodium chloride? A B C D

When dilute hydrochloric acid is added to aqueous lead(II) nitrate, a white precipitate of lead(II) chloride is formed. What is the ionic equation for this reaction? A ${\text{Pb}}^{2+}\text{(aq)}+2\text{HCl(aq)}\to {\text{PbCl}}_2\text{(s)}+2{\text{H}}^{+}\text{(aq)}$ B ${\text{Pb}}^{2+}\text{(aq)}+2\text{HCl(aq)}+2{\text{HNO}}_3\text{(aq)}\to {\text{PbCl}}_2\text{(s)}+4{\text{H}}^{+}\text{(aq)}+2{\text{NO}}_3^{-}\text{(aq)}$ C ${\text{Pb}}^{2+}\text{(aq)}+2{\text{Cl}}^{-}\text{(aq)}\to {\text{PbCl}}_2\text{(s)}$ D ${\text{Pb(NO}}_3{)}_2\text{(aq)}+2\text{HCl(aq)}\to {\text{Pb}}^{2+}\text{(aq)}+2{\text{Cl}}^{-}\text{(aq)}+2{\text{HNO}}_3\text{(aq)}$

Which row shows a pair of molecules where the $M_r$ of compound X is exactly half that of compound Y? [$A_r$: C, 12; Cl, 35.5; H, 1; O, 16]

One volume of a gaseous element, ${\text{X}}_2$, combines with an equal volume of gaseous hydrogen to form two volumes of a gaseous hydride. What is the formula for the hydride of X? A ${\text{H}}_2\text{X}$ B $\text{HX}$ C ${\text{HX}}_2$ D ${\text{H}}_2{\text{X}}_2$

Which reaction would produce the greatest volume of carbon dioxide at room temperature and pressure? [$M_r$: ${\text{CaCO}}_3$, 100; ${\text{Na}}_2{\text{CO}}_3$, 106; ${\text{CuCO}}_3$, 124] A burning $1\text{ g}$ of carbon in excess oxygen $$\text{C(s)}+{\text{O}}_2\text{(g)}\to {\text{CO}}_2\text{(g)}$$ B thermal decomposition of $10\text{ g}$ of calcium carbonate in the air $${\text{CaCO}}_3\text{(s)}\to \text{CaO(s)}+{\text{CO}}_2\text{(g)}$$ C adding $10\text{ g}$ of sodium carbonate to an excess of dilute hydrochloric acid $${\text{Na}}_2{\text{CO}}_3\text{(s)}+2\text{HCl(aq)}\to 2\text{NaCl(aq)}+{\text{CO}}_2\text{(g)}+{\text{H}}_2\text{O(l)}$$ D adding $50{\text{ cm}}^3$ of $1\text{ mol}\mathrm{/}{\text{dm}}^3$ sulfuric acid to an excess of copper carbonate $${\text{CuCO}}_3\text{(s)}+{\text{H}}_2{\text{SO}}_4\text{(aq)}\to {\text{CuSO}}_4\text{(aq)}+{\text{CO}}_2\text{(g)}+{\text{H}}_2\text{O(l)}$$

Chrome alum is the common name for a salt which has the formula ${\text{CrK(SO}}_4{)}_2$. What is the percentage by mass of chromium in chrome alum? A 17.3 B 18.4 C 20.7 D 21.3

The equation shows the production of iron by the reduction of iron(III) oxide. $${\text{Fe}}_2{\text{O}}_3+3\text{CO}\to 2\text{Fe}+3{\text{CO}}_2$$ 80 tonnes of iron(III) oxide produces 50 tonnes of iron. What is the percentage yield? A 45% B 63% C 68% D 89%

Aqueous copper(II) sulfate is electrolysed using copper electrodes. Which row correctly describes what happens?

Hydrogen reacts with chlorine to form hydrogen chloride. $${\text{H}}_2\text{(g)}+{\text{Cl}}_2\text{(g)}\to 2\text{HCl(g)}$$ The enthalpy change, $\mathrm{\Delta }H$, for this reaction can be calculated using bond energies.

What is the value of $\mathrm{\Delta }H$ for this reaction? A $-247\text{ kJ}\mathrm{/}\text{mol}$ B $-184\text{ kJ}\mathrm{/}\text{mol}$ C $+184\text{ kJ}\mathrm{/}\text{mol}$ D $+247\text{ kJ}\mathrm{/}\text{mol}$

Nitrogen and oxygen react as shown. $${\text{N}}_2\text{(g)}+2{\text{O}}_2\text{(g)}\to 2{\text{NO}}_2\text{(g)}$$ The enthalpy change for the reaction shown is $+66\text{ kJ}$. If two moles of nitrogen and two moles of oxygen are used, what will be the enthalpy change? A $+16.5\text{ kJ}$ B $+33\text{ kJ}$ C $+66\text{ kJ}$ D $+132\text{ kJ}$

Physical changes and chemical changes can occur in substances. Which process describes a chemical change? A covalent bonds in methane molecules are broken B intermolecular attractions between water molecules are broken C ionic bonds in a sodium chloride lattice are broken D the manufacture of brass from copper and zinc

Two methods used by students to measure the rate of a reaction are the 'disappearing cross' method and the 'loss of mass' method. ● For the 'disappearing cross' method, the student measures the time taken for the reaction mixture to go cloudy. ● For the 'loss of mass' method, the student measures the loss of mass over a known time interval. The rates of two reactions are investigated. reaction 1 Warm aqueous silver nitrate is added to chlorobutane dissolved in ethanol. Two products are formed. One is an organic compound which is soluble in ethanol and the other is silver chloride which is insoluble in ethanol. reaction 2 Pieces of solid calcium carbonate are added to dilute hydrochloric acid. Which method should be used for each reaction?

Hydrogen is used as a reactant both in the Haber process and in its addition to alkenes. Which row is correct?

Chlorine, ${\text{Cl}}_2$, reacts with iron(II), ${\text{Fe}}^{2+}$, ions. $${\text{Cl}}_2+2{\text{Fe}}^{2+}\to 2{\text{Cl}}^{-}+2{\text{Fe}}^{3+}$$ Which statement about this reaction is correct? A Chlorine is oxidised. B ${\text{Cl}}^{-}$ ions are formed by loss of electrons. C ${\text{Fe}}^{2+}$ ions have gained electrons. D ${\text{Fe}}^{3+}$ ions are formed by oxidation.

Which statement is correct? A A base will react with an ammonium salt to produce a gas that turns damp blue litmus paper red. B Adding a base to an acidic solution will increase the pH of the solution. C Aqueous sodium hydroxide is an alkali but not a base. D In a neutralisation reaction, a base donates a proton to an acid.

Information about three oxides, Q, R and T, is given. Q reacts with dilute sulfuric acid to form a salt and water. R reacts with both acids and bases to form a salt and water. T reacts with aqueous sodium hydroxide to form a salt and water. Using only this information, which row correctly classifies the three oxides?

Which definition of a hydrated substance is correct? A A hydrated substance is a soluble ionic compound such as barium sulfate. B A hydrated substance is an ionic compound that contains no water. C A hydrated substance is one that is chemically combined with hydrogen. D A hydrated substance is one that is chemically combined with water.

A student has five reagents. ● dilute hydrochloric acid ● dilute sulfuric acid ● dilute nitric acid ● solid calcium carbonate ● solid copper(II) carbonate How many soluble salts can be prepared from these five reagents? A 3 B 4 C 5 D 6

The table shows the number of electrons in one atom of each of the elements W, X, Y and Z.

Which statement is correct? A W and Z are in the same group. B X is a metal. C X and Y will form the compound ${\text{X}}_3\text{Y}$. D Y is a non-metal.

Some properties of elements in Group VII and the reasons for these properties are shown. Which row shows a property and the reason for this property?

Aircraft manufacture requires a metal that: 1 has a relatively low density 2 is resistant to corrosion. Which properties apply to aluminium? A both 1 and 2 B 1 only C 2 only D neither 1 nor 2

Which diagram represents an alloy? A B C D

A small piece of metal is added to a large beaker of water. A vigorous reaction occurs. When the reaction stops, a few drops of litmus are added to the solution. What is the metal and which colour is the solution after the litmus is added?

The rusting of iron can be prevented by coating the iron with another material. Which statement explains why coating with zinc is more effective than painting? A If the coating is damaged, zinc corrodes instead of iron. B Iron is above zinc in the reactivity series. C Zinc does not react with air or with water. D Zinc forms an unreactive alloy coating with iron.

The list shows the position of metal X in the reactivity series of metals. $$\text{Na}\text{Al}\text{Fe}\text{X}\text{Cu}\text{Ag}$$ Which methods could be used to extract metal X? 1 electrolysis of the solid metal oxide 2 heating the metal oxide with carbon 3 heating the metal oxide with copper A 1, 2 and 3 B 1 and 2 only C 2 only D 2 and 3 only

Which statement about water is correct? A Distillation is used to remove insoluble impurities from the domestic water supply. B Water containing impurities turns anhydrous copper(II) sulfate blue. C Water containing impurities turns cobalt(II) chloride paper blue. D Water containing impurities boils at $100{}^{\circ }\text{C}$.

Some compounds that can be used as fertilisers are listed. ● ammonium nitrate ● potassium nitrate ● potassium phosphate ● sodium phosphate Three of the elements required for plant growth have the atomic symbols N, P and K. How many of these three elements are present in each of the compounds?

Different strategies to reduce the effects of environmental issues have been suggested. Which row is correct?

Which statement about organic compounds is correct? A Each molecule of propan-1-ol has one $-\text{OH}$ group and each molecule of propan-2-ol has two $-\text{OH}$ groups. B Octane and decane are in a homologous series with the general formula ${\text{C}}_n{\text{H}}_{2n}$. C The ester butyl butanoate has eight carbon atoms in each molecule. D The structure of the functional group in a carboxylic acid is $-\text{C}-\text{O}-\text{O}-\text{H}$.

In the fractional distillation of petroleum, different fractions are obtained at the top and bottom of the fractionating column. Which properties does the fraction obtained at the top of the fractionating column have, compared with the fraction obtained at the bottom? 1 higher viscosity 2 lower boiling point 3 lower volatility 4 shorter chain length A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

A chlorine atom can replace a hydrogen atom in a molecule of butane, ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{CH}}_3$, to form chlorobutane. How many different structural isomers of chlorobutane can be formed? A 1 B 2 C 3 D 4

Two statements are shown. 1 When ethanol is made from glucose by fermentation, each glucose molecule produces three molecules of ethanol. 2 When ethanoic acid is made from ethanol, the ethanol acts as an oxidising agent. Which row about these statements is correct?

key ✓ = true ✗ = false

Polymer X is an addition polymer. The monomer used to make X is but-1-ene. Polymer Y is a condensation polymer. The monomers used to make Y are ${\text{HOCH}}_2{\text{CH}}_2\text{OH}$ and ${\text{HOOCCH}}_2\text{COOH}$. Which statement about X and Y is correct? A The repeat unit of X is $[{\text{CH(CH}}_3){\text{CH(CH}}_3)]$ and Y is a polyamide. B The repeat unit of X is $[{\text{CH(CH}}_3){\text{CH(CH}}_3)]$ and Y is a polyester. C The repeat unit of X is $[{\text{CH}}_2{\text{CH(C}}_2{\text{H}}_5)]$ and Y is a polyamide. D The repeat unit of X is $[{\text{CH}}_2{\text{CH(C}}_2{\text{H}}_5)]$ and Y is a polyester.

Which statement is correct? A A filtrate is a substance that remains on the filter paper after filtration. B A saturated solution has the maximum amount of solvent dissolved in the solute. C A solution is a compound produced when a solute reacts with a solvent. D A substance that remains in the heated flask after distillation is called a residue.

The diagram shows a chromatogram. Which spot has an $R_f$ value of 0.75? A B C D

The results of some tests on polluted river water are shown.

Which metal ion must be present in the water? A ${\text{Al}}^{3+}$ B ${\text{Ca}}^{2+}$ C ${\text{Fe}}^{2+}$ D ${\text{Zn}}^{2+}$