Electrolysis — Paper 3 · IGCSE Science - Combined 0653

8 (a) Water is extracted from a river and then treated to make it suitable for people to use. Two processes, J and chlorination, are used in the purification of the water supply, as shown in Fig. 8.1. river process J chlorination Fig. 8.1 (i) Process J removes insoluble solids from the water. Name process J. … [1] (ii) Explain why chlorine is added to the water supply. … … [1] (iii) Describe a chemical test for chlorine gas. State the positive result of this test. test … result … … [2] (b) Hydrogen chloride is formed when chlorine reacts with hydrogen. (i) Construct the word equation for this reaction. + [1] (ii) State the type of chemical bond that forms between non-metallic elements such as chlorine and hydrogen. Describe how electrons are involved in this bond. bonding type … explanation … … [2] (iii) In a molecule of hydrogen chloride, an atom of hydrogen is bonded to an atom of chlorine. State the formula of hydrogen chloride. … [1] (c) Chlorine is made during the electrolysis of aqueous copper chloride using inert electrodes. (i) Name the electrode at which chlorine forms during this process. … [1] (ii) State the product that forms at the other electrode. … [1] (iii) Identify the electrolyte used in this process. … [1]

11 marks

Mark scheme: 8(a)(i) filtration ; 1 8(a)(ii) kill microbes / sterilise (water) ; 1 8(a)(iii) (damp) litmus (paper) ; turns white / bleached ; 2 8(b)(i) ; LHS either order chlorine + hydrogen Æ hydrogen chloride 1 8(b)(ii) covalent ; share (pair of) electrons ; 2 8(b)(iii) HCl ; 1 8(c)(i) anode ; 1 8(c)(ii) copper ; 1 8(c)(iii) copper chloride solution / aqueous copper chloride ; 1

This question in 0653/32 May/June 2017

2 (a) Electrolysis is used to break up some compounds into simpler substances. Fig. 2.1 shows the electrolysis of molten lead(II) bromide using inert electrodes. low voltage d.c.supply negative electrode positive electrode – + molten lead(II) bromide Fig. 2.1 (i) State the names of the negative electrode and of the positive electrode. negative electrode … positive electrode … [1] (ii) Identify the substances formed at the negative electrode and at the positive electrode. at negative electrode … at positive electrode … [2] (iii) State the type of chemical bonding in compounds that are broken up by electrolysis. … [1] (iv) Electrolysis results in a chemical change. Explain what is meant by the term chemical change. … … … [1] (b) Potassium chloride is made when solid potassium carbonate reacts with an acid. A gas is made during this reaction. (i) Name the acid that reacts with potassium carbonate to form potassium chloride. … [1] (ii) Describe the change of the pH of the solution during the reaction. … [1] (iii) Describe a test to show that the colourless solution formed by this reaction contains chloride ions. test … observation … [2]

9 marks

Mark scheme: 2(a)(i) (negative) cathode and (positive) anode ; 1 2(a)(ii) (negative) lead ; (positive) bromine / Br2 ; 2 2(a)(iii) ionic / electrovalent ; 1 2(a)(iv) new substance(s) made ; 1 2(b)(i) hydrochloric (acid) / HCl ; 1 2(b)(ii) Increases ; 1 2(b)(iii) (test) (acidified) silver nitrate ; (observation) white precipitate / solid ; 2

This question in 0653/31 Oct/Nov 2017

5 (a) The Periodic Table lists all of the elements in atomic number order. Define atomic number. … … [1] (b) Part of the Periodic Table is shown in Fig. 5.1. The letters in this table are not the symbols of the elements. I II III IV V VI VII VIII A B C D E F G H Fig. 5.1 (i) Use the letters in Fig. 5.1 to identify one element that is an unreactive gas, … the element with the lowest mass (nucleon) number … . [2] (ii) State the type of chemical bond that forms between element D and element E. … [1] (iii) Element F and element B combine in an exothermic reaction. State what is meant by exothermic. … … [1] (c) Chlorine gas is bubbled through a solution of potassium bromide, as shown in Fig. 5.2. chlorine gas potassium bromide solution Fig. 5.2 (i) State the colour of chlorine gas. … [1] (ii) The solution of potassium bromide turns from colourless to orange-brown. Name the orange-brown substance. … [1] (d) A student tries to produce chlorine gas using the apparatus shown in Fig. 5.3. low voltage d.c. supply – + inert carbon rods solid copper chloride Fig. 5.3 No chlorine gas is made. (i) Name the process that the student is trying to use. … [1] (ii) Suggest one change that the student must make to produce chlorine gas. …

9 marks

Mark scheme: 5(a) number of protons in an atom / nucleus ; 1 5(b)(i) C ; A ; 2 5(b)(ii) ionic / electrovalent ; 1 5(b)(iii) releases heat / thermal energy / temperature goes up / gets hotter ; 1 5(c)(i) (pale) green ; 1 5(c)(ii) bromine / Br2 ; 1 5(d)(i) electrolysis ; 1 Question Answer Marks 5(d)(ii) add water / use (copper chloride) solution ; 1

This question in 0653/32 Oct/Nov 2017

8 (a) Molten lead(II) bromide is broken down into simpler substances using the apparatus shown in Fig. 8.1. low voltage d.c.supply … … – + molten lead (II) bromide Fig. 8.1 (i) Use the names of the electrodes to complete Fig. 8.1. [2] (ii) Describe the appearance of the substance that forms at the positive electrode. … [1] (b) Copper is extracted from copper oxide by heating with carbon. The equation for this reaction is copper oxide + carbon copper + carbon dioxide. State whether the copper oxide is oxidised or reduced during this reaction. Explain your answer. … … [1] (c) Copper, Cu, does not react with water. Calcium, Ca, reacts rapidly with water. Magnesium, Mg, reacts slowly with water. Potassium, K, reacts very rapidly with water. Place these four metals in order of reactivity, from most to least reactive. … most reactive … … … least reactive [2] (d) A student adds excess magnesium to dilute hydrochloric acid. (i) State two changes that the student can make to increase the rate of this reaction. 1. … 2. … [2] (ii) Identify the salt produced during this reaction. … [1] (iii) After the reaction finishes, the student removes the unreacted magnesium from the solution that has formed. Name the separation technique that the student uses. … [1]

10 marks

Mark scheme: 8(a)(i) (left) cathode ; (right) anode ; 2 8(a)(ii) orange / brown gas ; 1 8(b) (reduced) oxygen is removed ; 1 8(c) K Ca Mg Cu ;; 2 8(d)(i) any two from heat / increase temperature ; increase surface area of magnesium ; increase concentration of acid ; use / add a catalyst ; 2 8(d)(ii) magnesium chloride ; 1 8(d)(iii) filter / filtration ; 1

This question in 0653/33 Oct/Nov 2017

2 (a) Copper is extracted from a substance using the apparatus shown in Fig. 2.1. low voltage d.c. supply − + … … … Fig. 2.1 (i) Name this process. … [1] (ii) Complete Fig. 2.1 by labelling the anode, cathode and electrolyte. [2] (iii) Name one compound that can be used in this process to extract copper at room temperature. … [1] (iv) State what is done to this solid compound before it can be used in this process. … [1] (v) State whether this process for the extraction of copper involves a chemical change or a physical change. Explain your answer. change … explanation … … [1] (b) A student finds out that copper can also be extracted by heating a different compound, copper oxide, with a non-metallic element. (i) Name this non-metallic element. … [1] (ii) Name the type of chemical reaction in which copper oxide is changed to copper. … [1] (c) Copper is one element in a collection of metals which have high melting points, high densities and often act as catalysts. (i) Suggest one other property that is shown by these metals that is not shown by other metals. … [1] (ii) State the effect of a catalyst on a chemical reaction. … [1]

10 marks

Mark scheme: 2(a)(i) electrolysis ; 1 2(a)(ii) ;; all three correct (2) one or two correct (1) 2 cathode anode electrolyte Question Answer Marks 2(a)(iii) copper chloride / other soluble copper compound ; 1 2(a)(iv) dissolve in water ; 1 2(a)(v) chemical and new substance(s) made ; 1 2(b)(i) carbon / hydrogen ; 1 2(b)(ii) reduction ; 1 2(c)(i) form coloured compounds ; 1 2(c)(ii) increases reaction rate ; 1

This question in 0653/32 Feb/March 2018

2 (a) Complete the following sentences using words from the list. Each word may be used once, more than once or not at all. atoms compounds covalent elements ionic ions mixtures molecules (i) The smallest parts of an element are … . [1] (ii) All … contain atoms joined by sharing pairs of electrons in … bonds. [2] (iii) Atoms which lose or gain electrons form particles called … . [1] (iv) Elements in … cannot be separated by simple physical processes. Substances in … can be separated by simple physical processes. [2] (b) A student passes an electric current through aqueous copper chloride using the apparatus shown in Fig. 2.1. low voltage d.c. supply brown solid gas bubbles aqueous copper chloride Fig. 2.1 (i) Complete the labels in Fig. 2.1 by naming the two electrodes. [2] (ii) Name the solid and the gas formed in this process. solid … gas … [2]

10 marks

Mark scheme: 2(a)(i) atoms ; 1 2(a)(ii) molecules ; covalent ; 2 2(a)(iii) ions ; 1 2(a)(iv) compounds/molecules ; mixture ; 2 Question Answer Marks 2(b)(i) (left electrode) cathode ; (right electrode) anode ; 2 2(b)(ii) (solid) copper / Cu ; (gas) chlorine / Cl2 ; 2

This question in 0653/31 Oct/Nov 2018

8 (a) A teacher uses the apparatus shown in Fig. 8.1 to demonstrate the electrolysis of lead(II) bromide. low voltage d.c. supply solid lead(II) bromide Fig. 8.1 Predict whether this electrolysis works. Explain your answer. prediction … explanation … … … [1] (b) A student electrolyses aqueous copper chloride using the apparatus shown in Fig. 8.2. low voltage d.c. supply aqueous copper chloride Fig. 8.2 Copper forms on the negative electrode. A gas forms at the positive electrode. The student tests this gas with damp litmus paper. Name the gas and predict its effect on the colour of the litmus paper. name … effect … [2] (c) Copper can be extracted by heating copper oxide with carbon. The equation for this reaction is: copper oxide + carbon carbon dioxide + copper Identify one substance which is oxidised and one substance which is reduced during this reaction. oxidised … reduced … [2] (d) Carbon dioxide is present in clean air in small quantities. (i) Name one other gas which is present in clean air in small quantities. … [1] (ii) Name two substances present in clean air which cause rusting. 1. … 2. … [1]

7 marks

Mark scheme: 8(a) (prediction) no reaction AND (explanation) lead bromide is solid / needs to be molten / liquid ; 1 8(b) (name) chlorine ; (effect) bleaches / (turns) white / decolourises ; 2 8(c) (oxidised) carbon ; (reduced) copper oxide ; 2 8(d)(i) water (vapour) / noble gas / named noble gas ; 1 8(d)(ii) oxygen / O2 AND water (vapour) / H2O ; 1

This question in 0653/32 Oct/Nov 2018

5 (a) Sodium is a Group I metal. An atom of sodium is represented by the symbol 23Na11 (i) State the numbers of electrons, neutrons and protons in this atom. electrons … neutrons … protons … [2] (ii) The electronic structure of a sodium atom is shown in Fig. 5.1a. Fig. 5.1a Fig. 5.1b Complete Fig. 5.1b to show the electronic structure of a sodium ion. [1] (b) Apparatus used in the electrolysis of concentrated aqueous sodium chloride is shown in Fig. 5.2. low voltage d.c. supply – + concentrated aqueous sodium chloride Fig. 5.2 Complete the sentences about the electrolysis of concentrated aqueous sodium chloride. The concentrated aqueous sodium chloride is known as the … . The positive electrode is called the … , and the negative electrode is called the … . At the positive electrode … forms and at the negative electrode … forms. [5] (c) When a teacher adds a piece of sodium to a bowl of water, an exothermic reaction occurs. The teacher uses Universal Indicator to test the solution in the bowl after the reaction. (i) Describe a simple method that the teacher can use to show that the reaction is exothermic. … … … [2] (ii) Describe and explain the effect of the solution in the bowl on the Universal Indicator. effect … explanation … … [2] [Total: 12]

12 marks

Mark scheme: 5(a)(i) (electrons) 11 AND (protons) 11 ; (neutrons) 12 ; 2 5(a)(ii) 2, 8 ; 1 5(b) electrolyte ; anode ; cathode ; chlorine (gas) ; hydrogen (gas) ; 5 5(c)(i) uses a thermometer to measure temperature (before and after) ; temperature should show an increase / idea that heat is given out ; 2 5(c)(ii) (effect) (turns) blue ; (explanation) (forms) (sodium) hydroxide / alkaline (solution) ; 2

This question in 0653/32 Feb/March 2019

2 (a) Sodium chloride is an ionic compound. It dissolves in water. Water is a covalent compound. (i) State the formula of sodium chloride. … [1] (ii) Describe the formation of ionic bonds and of covalent bonds. Use ideas about electrons in your answer. ionic bonds … … … covalent bonds … … … [2] (iii) Use the words solvent, solute and solution to describe sodium chloride, water and aqueous sodium chloride. Sodium chloride is a … . Water is a … . Aqueous sodium chloride is a … . [2] (b) A student uses the apparatus shown in Fig. 2.1 for the electrolysis of concentrated aqueous sodium chloride. low voltage d.c. supply – + inert electrodes concentrated aqueous sodium chloride Fig. 2.1 (i) State whether this electrolysis is a physical change or a chemical change. Explain your answer. change … explanation … … [1] (ii) Name the non-metallic element used to make the inert electrodes. … [1] (iii) Name the positive and the negative electrodes. positive … negative … [1] (iv) During this electrolysis two gases are produced. Identify the gases produced at the positive and at the negative electrodes. positive … negative … [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) 1 2(a)(ii) (ionic) electrons lost and gained ; (covalent) electrons shared ; 2 2(a)(iii) (sodium chloride) solute (water) solvent (aq NaCl) solution ;; all three correct (2) one or two correct (1) 2 2(b)(i) (change) chemical and (explanation) new substance(s) made ; 1 2(b)(ii) carbon / C ; 1 Question Answer Marks 2(b)(iii) (positive) anode and (negative) cathode ; 1 2(b)(iv) (positive) chlorine / Cl2 ; (negative) hydrogen / H2 ; 2

This question in 0653/32 May/June 2019

5 (a) The electrolysis of concentrated aqueous sodium chloride is shown in Fig. 5.1. low voltage d.c. supply … … – + … Fig. 5.1 (i) Complete Fig. 5.1 by adding the labels anode, cathode and electrolyte. [2] (ii) One of the products of this electrolysis is chlorine gas. Identify the two other products. 1. … 2. … [2] (iii) Describe a chemical test for chlorine gas and state the positive result. test … … result … [2] (b) An atom of sodium has atomic number 11 and nucleon number 23. State the number of protons and the number of neutrons in this atom of sodium. protons … neutrons … [2] (c) A chlorine atom has 17 electrons. A chloride ion has the symbol Cl –. Complete Fig. 5.2 to show the electron arrangements in a chlorine atom and in a chloride ion. × × × × chlorine atom chloride ion Fig. 5.2 [2] [Total: 10]

10 marks

Mark scheme: 5(a)(i) all three correct = 2 marks one or two correct = 1 mark 2 5(a)(ii) sodium hydroxide / NaOH ; hydrogen / H2 ; 2 5(a)(iii) (test) damp litmus paper ; (result) (blue / red to) white ; 2 5(b) (protons) 11 ; (neutrons) 12 ; 2 5(c) (chlorine atom) 2, 8, 7 drawn ; (chloride ion) 2, 8, 8 drawn ; 2

This question in 0653/32 Oct/Nov 2019

5 (a) The electrolysis of concentrated aqueous sodium chloride is shown in Fig. 5.1. low voltage d.c. supply … … – + … Fig. 5.1 (i) Complete Fig. 5.1 by adding the labels anode, cathode and electrolyte. [2] (ii) One of the products of this electrolysis is chlorine gas. Identify the two other products. 1. … 2. … [2] (iii) Describe a chemical test for chlorine gas and state the positive result. test … … result … [2] (b) An atom of sodium has atomic number 11 and nucleon number 23. State the number of protons and the number of neutrons in this atom of sodium. protons … neutrons … [2] (c) A chlorine atom has 17 electrons. A chloride ion has the symbol Cl –. Complete Fig. 5.2 to show the electron arrangements in a chlorine atom and in a chloride ion. × × × × chlorine atom chloride ion Fig. 5.2 [2] [Total: 10]

10 marks

Mark scheme: 5(a)(i) all three correct = 2 marks one or two correct = 1 mark 2 5(a)(ii) sodium hydroxide / NaOH ; hydrogen / H2 ; 2 5(a)(iii) (test) damp litmus paper ; (result) (blue / red to) white ; 2 5(b) (protons) 11 ; (neutrons) 12 ; 2 5(c) (chlorine atom) 2, 8, 7 drawn ; (chloride ion) 2, 8, 8 drawn ; 2

This question in 0653/33 Oct/Nov 2019

8 Sodium chloride, NaCl, is an ionic compound. (a) Name one method of obtaining solid sodium chloride from aqueous sodium chloride. … [1] (b) The electronic structures of an atom of sodium, Na, and of an atom of chlorine, Cl, are shown in Fig. 8.1. Na Cl atom atom Fig. 8.1 Complete Fig. 8.2 to show the electronic structure of a sodium ion, Na+, and of a chloride ion, Cl –. Na+ Cl – ion ion Fig. 8.2 [2] (c) Concentrated aqueous sodium chloride is electrolysed using inert electrodes, as shown in Fig. 8.3. low voltage d.c. supply – + concentrated aqueous sodium chloride Fig. 8.3 Complete the word equation for the electrolysis of concentrated aqueous sodium chloride. concentrated aqueous sodium + + sodium hydroxide chloride [2] (d) Suggest the pH of aqueous sodium hydroxide and its effect on the colour of Universal Indicator. pH … colour … [2] (e) State the effect of chlorine gas on damp litmus paper. … [1] [Total: 8]

8 marks

Mark scheme: 8(a) evaporate ; allow distil / crystallise / boil 1 8(b) drawn: Na+ 2, 8 ; Cl– 2, 8, 8 ; 2 8(c) (either order) concentrated aqueous sodium chloride  sodium hydroxide + hydrogen ; + chlorine ; 2 8(d) pH > 7 to 14 ; colour blue-green / blue / purple ; 2 8(e) (blue / purple to) white / bleached ; 1

This question in 0653/32 Feb/March 2020

5 (a) In an experiment, carbon electrodes are used to pass an electric current through concentrated aqueous sodium chloride, as shown in Fig. 5.1. low voltage d.c. supply negative positive electrode electrode concentrated aqueous sodium chloride Fig. 5.1 (i) Name the process shown in Fig. 5.1. … [1] (ii) Identify the solvent in concentrated aqueous sodium chloride. … [1] (iii) Identify the products which form at the negative electrode and at the positive electrode. negative electrode product … positive electrode product … [2] (iv) Name the negative electrode and the positive electrode. negative electrode … positive electrode … [2] (b) Some metals are extracted from their ores by heating with carbon. (i) Identify one metal that is extracted from its ore by this method. … [1] (ii) In this extraction process, oxygen is removed from the metal. State the type of chemical reaction that involves the loss of oxygen. … [1] [Total: 8]

8 marks

Mark scheme: 5(a)(i) electrolysis ; 1 5(a)(ii) water / H2O ; 1 5(a)(iii) (negative electrode product) hydrogen / H2 ; (positive electrode product) chlorine / Cl2 ; 2 5(a)(iv) (negative electrode) cathode ; (positive electrode) anode ; 2 5(b)(i) copper ; 1 5(b)(ii) reduction ; 1

This question in 0653/32 Oct/Nov 2020

8 (a) An atom of lead is represented by the symbol shown. 207 Pb 82 (i) Deduce the number of electrons and number of neutrons in this atom. electrons … neutrons … [2] (ii) The proton number (atomic number) of lead is 82. Define the term proton number. … … [1] (iii) State the charges of protons, neutrons and electrons. protons … neutrons … electrons … [1] (b) Lead is extracted from molten lead(II) bromide using the apparatus shown in Fig. 8.1. low voltage d.c. supply – + molten lead(II) bromide Fig. 8.1 (i) Name the process shown in Fig. 8.1. … [1] (ii) State the name of the electrode at which lead forms. … [1] (c) Lead is extracted from lead(II) oxide, PbO, by heating with carbon. Carbon dioxide is also made in this endothermic reaction. (i) Describe what is meant by an endothermic reaction. … … [1] (ii) Complete the word equation for this reaction. + lead + [1] (iii) Circle the word to show whether lead(II) oxide is oxidised or reduced in this reaction. Explain your answer. oxidised reduced explanation … … (d) A teacher has a different compound of lead. When this compound of lead reacts with dilute hydrochloric acid, carbon dioxide is formed. Suggest the name of this compound of lead. … [1] [Total: 10]

10 marks

Mark scheme: 8(a)(i) (electrons) 82 ; (neutrons) 125 ; 2 8(a)(ii) the number of protons in the nucleus of an atom ; 1 8(a)(iii) (protons) +1 (neutrons) no charge (electrons) -1 ; all three needed for one mark 1 Question Answer Marks 8(b)(i) electrolysis ; 1 8(b)(ii) cathode ; 1 8(c)(i) takes in, heat / energy ; 1 8(c)(ii) ; 1 8(c)(iii) reduced (circled) AND (explanation) loses oxygen ; 1 8(d) lead carbonate / PbCO3 ; 1

This question in 0653/32 Feb/March 2021

2 (a) Fig. 2.1 shows part of Group I of the Periodic Table. 3 Li lithium 7 11 Na sodium 23 19 K potassium 39 Fig. 2.1 (i) State the trend in the reactivity of the elements going down Group I. … [1] (ii) Explain why lithium does not react with helium, a Group VIII element. … … [1] (iii) Lithium is a solid and helium is a gas. Describe two differences between the structures of a solid and a gas. 1 … … 2 … … [2] (b) A piece of sodium is added to water, as shown in Fig. 2.2. sodium water Fig. 2.2 The sodium reacts with water. The reaction is exothermic. (i) State one other observation that is seen when sodium reacts with water. … [1] (ii) Complete the word equation for the reaction of sodium with water. sodium + water + [2] (c) X is a compound that reacts with dilute hydrochloric acid to form sodium chloride and water. Suggest the identity of X. … [1] (d) Concentrated aqueous sodium chloride is broken down by electrolysis. (i) State the type of chemical bond in sodium chloride. … [1] (ii) Identify the product that forms at the anode (positive electrode). … [1] [Total: 10]

10 marks

Mark scheme: 2(a)(i) increasing / more reactive / faster reaction ; 1 2(a)(ii) helium / He is, unreactive / inert ; 1 2(a)(iii) any two from: (solid/lithium) particles close(r) (together) ORA ; (solid/lithium) particles regular arrangement ORA ; (solid/lithium) particles vibrate / not free-moving ORA ; 2 Question Answer Marks 2(b)(i) fizzes / bubbles OR gets smaller / disappears OR moves around ; 1 2(b)(ii) sodium + water → sodium hydroxide + hydrogen in either order sodium hydroxide ; hydrogen ; 2 2(c) sodium hydroxide / NaOH OR sodium carbonate / Na2CO3 ; 1 2(d)(i) ionic ; 1 2(d)(ii) chlorine / Cl2 ; 1

This question in 0653/31 May/June 2021

5 (a) An electric current is passed through an aqueous solution of compound X using inert electrodes. Compound X is broken down by this process. The apparatus used is shown in Fig. 5.1. low voltage d.c. supply negative positive electrode electrode aqueous solution of compound X Fig. 5.1 (i) Name this process. … [1] (ii) State the name of the negative electrode. … [1] (iii) Suggest the name of the element from which the electrodes are made. … [1] (iv) Deduce the type of bonding present in compound X. … [1] (v) During this process a gas is formed at the positive electrode. This gas bleaches damp litmus paper. Identify this gas. … [1] (vi) State whether the type of change occurring when an electric current is passed through the aqueous solution of compound X is a chemical change or a physical change. Explain your answer. type of change … explanation … … [1] (b) An aqueous solution of compound X is a mixture. (i) Describe the difference between a compound and an element. … … [1] (ii) Describe the difference between a compound and a mixture. … … [1] (c) An aqueous solution of compound X contains compound X dissolved in water. (i) Describe one chemical test that shows the presence of water. State the observation for a positive result. test … observation … … [2] (ii) State one method of separation that can be used to collect pure water from an aqueous solution of compound X. … [1] [Total: 11]

11 marks

Mark scheme: 5(a)(i) electrolysis ; 1 5(a)(ii) cathode ; 1 5(a)(iii) platinum / carbon ; 1 5(a)(iv) ionic ; 1 5(a)(v) chlorine / Cl2 ; 1 5(a)(vi) (type of change) chemical AND (explanation) new substances are made ; 1 5(b)(i) element has only one type of atom ; OR compound contains two or more different types of atoms chemically joined ; 1 5(b)(ii) compound is one substance only; OR mixture contains two (or more) substances which can be separated physically / not joined together ; 1 5(c)(i) (test) (anhydrous) copper(II) sulfate OR (anhydrous)cobalt(II) chloride ; (result) (white) goes blue OR (blue) goes pink ; 2 5(c)(ii) distillation ; 1

This question in 0653/32 May/June 2022

2 (a) A beaker contains a mixture of sodium chloride dissolved in water and iron filings, as shown in Fig. 2.1. sodium chloride dissolved in water iron filings Fig. 2.1 (i) Identify the solute and the solvent in this mixture. solute … solvent … [2] (ii) Identify one compound in the mixture. … [1] (iii) State one method of removing the iron filings from the mixture. … [1] (b) When a dilute solution of sodium chloride dissolved in water is heated, evaporation occurs and the solution becomes more concentrated. State what is meant by more concentrated. Use ideas about particles in your answer. … … [1] (c) State the products at the anode and at the cathode when concentrated aqueous sodium chloride is electrolysed using inert electrodes. anode … cathode … [2] (d) An atom of iron is represented as shown. 5626Fe Deduce the number of electrons, protons and neutrons in this atom. electrons … protons … neutrons … [2] [Total: 9]

9 marks

Mark scheme: 2(a)(i) solute sodium chloride / salt / NaCl ; 2 solvent water / H2O; 2(a)(ii) water / H2O / sodium chloride / NaCl ; 1 2(a)(iii) filtration / filter / magnet; 1 2(b) a greater number of (sodium chloride) particles per unit volume ; 1 2(c) anode chlorine (gas) / Cl2 ; 2 cathode hydrogen (gas) / H2 ; 2(d) electrons 26 AND 2 protons 26 ; neutrons 30 ;

This question in 0653/32 Oct/Nov 2022

2 (a) A beaker contains a mixture of sodium chloride dissolved in water and iron filings, as shown in Fig. 2.1. sodium chloride dissolved in water iron filings Fig. 2.1 (i) Identify the solute and the solvent in this mixture. solute … solvent … [2] (ii) Identify one compound in the mixture. … [1] (iii) State one method of removing the iron filings from the mixture. … [1] (b) When a dilute solution of sodium chloride dissolved in water is heated, evaporation occurs and the solution becomes more concentrated. State what is meant by more concentrated. Use ideas about particles in your answer. … … [1] (c) State the products at the anode and at the cathode when concentrated aqueous sodium chloride is electrolysed using inert electrodes. anode … cathode … [2] (d) An atom of iron is represented as shown. 5626Fe Deduce the number of electrons, protons and neutrons in this atom. electrons … protons … neutrons … [2] [Total: 9]

9 marks

Mark scheme: 2(a)(i) solute sodium chloride / salt / NaCl ; 2 solvent water / H2O; 2(a)(ii) water / H2O / sodium chloride / NaCl ; 1 2(a)(iii) filtration / filter / magnet; 1 2(b) a greater number of (sodium chloride) particles per unit volume ; 1 2(c) anode chlorine (gas) / Cl2 ; 2 cathode hydrogen (gas) / H2 ; 2(d) electrons 26 AND 2 protons 26 ; neutrons 30 ;

This question in 0653/33 Oct/Nov 2022

5 Magnesium sulfate is produced by reacting excess magnesium oxide with dilute sulfuric acid. (a) Complete the word equation for this reaction. magnesium + + sulfate [2] (b) A coloured aqueous solution is used to measure the pH of dilute sulfuric acid. (i) State the name of the coloured aqueous solution that is used to measure the pH of acids and alkalis. … [1] (ii) Suggest the pH value of dilute sulfuric acid. … [1] (c) Complete the sentences about the preparation of salt crystals. Use words from the list. Each word may be used once, more than once or not at all. acid filtering heating magnesium distillation magnesium sulfate shaking solid Excess magnesium oxide is added to dilute sulfuric acid and stirred until no more … dissolves. Pure aqueous magnesium sulfate is separated by … . Some water is removed by gentle … . The solution is then left to form pure dry crystals of the salt called … . [4] (d) Magnesium sulfate contains magnesium ions, Mg2+. Describe how magnesium ions are formed from magnesium atoms. … [1] (e) Aqueous magnesium sulfate is broken down by an electric current. State the name of this process. … [1] [Total: 10]

10 marks

Mark scheme: 5(a) magnesium oxide + sulfuric acid  magnesium sulfate + water ;; LHS (1) RHS (1) 5(b)(i) universal indicator ; 1 5(b)(ii) 1 – 6 ; 1 5(c) solid ; filtering / filtration ; heating ; magnesium sulfate ; 4 5(d) loss of electrons ; 1 Question Answer Marks 5(e) electrolysis ; 1

This question in 0653/33 May/June 2023

8 Chlorine is in Group VII of the Periodic Table. (a) A chlorine atom has 17 electrons and nucleon number 35. (i) Complete Fig. 8.1 to show the electrons in this chlorine atom. Cl Fig. 8.1 [1] (ii) Deduce the number of neutrons in this chlorine atom. … [1] (b) Chlorine gas and aqueous sodium hydroxide are made when an electric current is passed through solution X. (i) State the name of the process that breaks down compounds by passing an electric current through them. … [1] (ii) Identify solution X. … [1] (c) The elements in Group VII exist as diatomic molecules. (i) State what is meant by the term diatomic. … … [1] (ii) Describe two trends in the properties of elements in Group VII, going down the group. 1 … 2 … [2] (d) Complete the sentences about the treatment of the water supply. Use one word in each gap. The process of … is used to remove insoluble particles from the water. The process of chlorination is used to kill … in the water. [2] [Total: 9]

9 marks

Mark scheme: 8(a)(i) (2,) 8, 7 ; 1 8(a)(ii) 18 ; 1 8(b)(i) electrolysis ; 1 8(b)(ii) (concentrated, aqueous) sodium chloride / NaCl ; 1 8(c)(i) (consisting of) two atoms ; 1 8(c)(ii) (become) darker in colour ; 2 change from gas to liquid to solid ; 8(d) filtration ; 2 bacteria / microorganisms / microbes ;

This question in 0653/31 Oct/Nov 2023

8 (a) Solid zinc and dilute sulfuric acid react to form zinc sulfate and hydrogen gas. Zn + H2SO4 ZnSO4 + H2 (i) A student measures and controls the temperature, the volume and the concentration of the acid. State two other measurements that the student needs to make to investigate the rate of this reaction. 1 … 2 … [2] (ii) Describe what happens to the pH number of the reaction mixture during the reaction. … [1] (b) Dilute sulfuric acid is electrolysed using the apparatus shown in Fig. 8.1. low voltage d.c. power supply negative positive electrode electrode dilute sulfuric acid Fig. 8.1 (i) State the name of the negative electrode. … [1] (ii) Identify the product that forms at the positive electrode. … [1] [Total: 5]

5 marks

Mark scheme: 8(a)(i) time ; and any one of: volume of gas / H2/ total mass / mass of hydrogen ; 2 8(a)(ii) (pH number) increases ; 1 8(b)(i) cathode ; 1 8(b)(ii) oxygen / O2 ; 1

This question in 0653/31 May/June 2024

5 Aluminium ore contains aluminium oxide. Aluminium is extracted from aluminium oxide in the process shown in Fig. 5.1. carbon cathode carbon anode – + molten mixture containing aluminium oxide molten aluminium Fig. 5.1 (a) (i) Circle the name of the process shown in Fig. 5.1. chromatography crystallisation electrolysis filtration [1] (ii) State the name of the ore that contains aluminium oxide. … [1] (b) Explain why the extraction of aluminium from aluminium oxide is a reduction reaction. … … [1] (c) An atom of aluminium is represented as shown. 27 13Al (i) Describe what is meant by nucleon number. … … [1] (ii) Deduce the number of neutrons in this atom. … [1] (d) The electronic structure of an aluminium atom is shown in Fig. 5.2. Al Fig. 5.2 When aluminium reacts, aluminium atoms form aluminium ions. Complete Fig. 5.3 to show the electronic structure of an aluminium ion. Al Fig. 5.3 [1] (e) Aluminium oxide, Al2O3 , is an ionic compound. Ammonia, NH3 , is a covalent compound. Complete Table 5.1 to show the electrical conductivity of aluminium, aluminium oxide and ammonia as solids and as liquids. Use a tick (✓) to show an electrical conductor. Use a cross (✗) to show an electrical non‑conductor. Two have been done for you. Table 5.1 Key aluminium aluminium oxide ammonia ✓ = electrical solid ✓ ✗ conductor ✗ = electrical liquid non‑conductor [2] [Total: 8]

8 marks

Mark scheme: 5(a)(i) electrolysis (circled) ; 1 5(a)(ii) bauxite ; 1 5(b) oxygen is lost ; 1 5(c)(i) the (total) number of protons and neutrons ; 1 5(c)(ii) 14 ; 1 5(d) 2 electrons in inner shell, 8 in second shell and none in third shell ; 1 5(e) ;; four correct = (2) two or three correct = (1) 2

This question in 0653/32 May/June 2024

8 Fig. 8.1 shows apparatus for the electrolysis of dilute sulfuric acid using inert electrodes. test-tube glass container dilute sulfuric acid Fig. 8.1 (a) (i) Label the cathode on Fig. 8.1. [1] (ii) State the name of the product formed at the: positive electrode … negative electrode. … [2] (iii) State the name of an element used to make inert electrodes. … [1] (b) State the formula of sulfuric acid. … [1] (c) Dilute sulfuric acid is the electrolyte in this electrolysis. Complete the sentence about electrolytes. Electrolytes must be in aqueous solution or … for electrolysis to occur. [1] [Total: 6]

6 marks

Mark scheme: 8(a)(i) right-hand electrode labelled cathode ; 1 8(a)(ii) positive electrode oxygen ; 2 negative electrode hydrogen ; 8(a)(iii) platinum / carbon ; 1 8(b) H2SO4 ; 1 8(c) molten ; 1

This question in 0653/32 Oct/Nov 2024

8 Fig. 8.1 shows apparatus for the electrolysis of dilute sulfuric acid using inert electrodes. test-tube glass container dilute sulfuric acid Fig. 8.1 (a) (i) Label the cathode on Fig. 8.1. [1] (ii) State the name of the product formed at the: positive electrode … negative electrode. … [2] (iii) State the name of an element used to make inert electrodes. … [1] (b) State the formula of sulfuric acid. … [1] (c) Dilute sulfuric acid is the electrolyte in this electrolysis. Complete the sentence about electrolytes. Electrolytes must be in aqueous solution or … for electrolysis to occur. [1] [Total: 6]

6 marks

Mark scheme: 8(a)(i) right-hand electrode labelled cathode ; 1 8(a)(ii) positive electrode oxygen ; 2 negative electrode hydrogen ; 8(a)(iii) platinum / carbon ; 1 8(b) H2SO4 ; 1 8(c) molten ; 1

This question in 0653/33 Oct/Nov 2024

6 Table 6.1 shows the products and observations at the electrodes in the electrolysis of three electrolytes. Table 6.1 negative electrode positive electrode electrolyte product observation product observation molten bubbles of lead grey liquid lead(II) bromide … red-brown gas concentrated bubbles of bubbles of aqueous hydrogen chlorine colourless gas green gas sodium chloride bubbles of bubbles of dilute sulfuric acid … colourless gas … colourless gas (a) Complete Table 6.1. [3] (b) Explain why the mass of concentrated aqueous sodium chloride decreases during electrolysis. … … [1] (c) Use Table 6.1 to explain why electrolysis is a chemical change. … … [1] (d) Inert electrodes are used in each electrolysis. Name one substance used as inert electrodes. … [1] (e) State the name of the negative electrode. … [1] (f) Electrolysis is an endothermic process. State the meaning of endothermic. … … [1] (g) Draw one straight line from each description to the correct substance. description substance chlorine salt that contains ionic bonds dilute sulfuric acid compound with a pH less than 7 hydrogen lead Group VII element lead(II) bromide [3] [Total: 11]

11 marks

Mark scheme: 6(a) bromine ; 3 hydrogen ; oxygen ; 6(b) products are gases (which are released) ; 1 6(c) new substances are formed / change cannot be directly reversed / cannot easily be reversed ; 1 6(d) platinum / carbon / graphite ; 1 6(e) cathode ; 1 6(f) a process that takes in (thermal) energy (from the surroundings) / a change where the temperature of the surroundings 1 decreases ; 6(g) 3 description substance chlorine salt that contains ionic dilute sulfuric bonds acid compound with a pH less hydrogen than 7 Group VII element lead lead(II) bromide ; ; ; each correct line = 1 mark

This question in 0653/32 Feb/March 2025

5 Dilute sulfuric acid is used in an electrolysis experiment. (a) Universal indicator is used to measure the pH of the dilute sulfuric acid. Describe how to use universal indicator to measure pH. … … … [2] (b) Fig. 5.1 shows the electrolysis. dilute sulfuric acid positive electrode negative electrode power supply Fig. 5.1 (i) Identify the gas formed at each electrode. negative electrode … positive electrode … [2] (ii) State the name of the positive electrode. … [1] (iii) Identify the electrolyte in this electrolysis. … [1] (c) The volume of gas formed at each electrode is measured every 30 s for 2 min. The results are shown in Table 5.1. Table 5.1 volume of gas at the volume of gas at the time negative electrode positive electrode / s / cm3 / cm3 0 0 0 30 18 9 60 36 18 90 54 27 120 36 (i) Use Table 5.1 to predict the volume of gas given off at the negative electrode at 120 s. volume = … cm3 [1] (ii) Use Table 5.1 to calculate the volume of gas formed per second at the positive electrode. volume = … cm3 / s [1] [Total: 8]

8 marks

Mark scheme: 5(a) (add UI to the acid and) look at the colour / state acid gives red colour ; 2 compare to a (pH number) chart ; 5(b)(i) negative electrode: hydrogen ; 2 positive electrode: oxygen ; 5(b)(ii) anode ; 1 5(b)(iii) (dilute) sulfuric acid ; 1 5(c)(i) 72 (cm3) ; 1 5(c)(ii) 0.3 (cm3 / s) ; 1

This question in 0653/33 May/June 2025