Chemistry 0620/42 October/November 2025: question paper and mark scheme

Question

The three states of matter are solid, liquid and gas. (a) Complete Table 1.1 to describe the structures of solids, liquids and gases in terms of particle separation, particle arrangement and particle motion. Table 1.1 state of matter particle separation particle arrangement particle motion solid touching liquid gas random random [3] (b) Substances can physically change. Name each physical change: • solid to liquid …… • gas to liquid …… • solid to aqueous. …… [3] (c) Gases diffuse. (i) Describe, in terms of particles, why gases diffuse. …… [1] (ii) State what determines the relative rate of diffusion of gases at constant temperature. …… [1] (d) Gaseous oxides of nitrogen are atmospheric pollutants. One adverse effect of oxides of nitrogen is the formation of acid rain. State two other adverse effects of oxides of nitrogen. 1 …… 2 …… [2] * 0000800000003 * DFD 3 (e) In a catalytic converter, oxides of nitrogen are removed by reaction with the toxic gaseous product of the incomplete combustion of hydrocarbon fuels. Two non-toxic gases are formed in this reaction. (i) Name the toxic gaseous product of the incomplete combustion of hydrocarbon fuels. …… [1] (ii) Name the two non-toxic gases formed in the catalytic converter. 1 …… 2 …… [2] [Total: 13] * 0000800000004 * DFD 4

Question

Iron is extracted from iron ore in a blast furnace. (a) The iron compound in the main iron ore used in the blast furnace is iron(III) oxide. (i) State the name of the main iron ore used in the blast furnace. …… [1] (ii) State how the main source of heat is provided in the blast furnace. …… [1] (iii) Name the gaseous reducing agent in the blast furnace. …… [1] (iv) Write a symbol equation for the reduction of iron(III) oxide by the gaseous reducing agent in (a)(iii). …… [2] (v) The main impurity in iron ore is silicon(IV) oxide. Write two symbol equations to show the role of limestone in removing silicon(IV) oxide from iron ore. 1 …… 2 …… [2] (b) Table 2.1 shows four different isotopes of iron, A, B, C and D. Table 2.1 A B C D 54Fe 56Fe 57Fe 58Fe Explain why A, B, C and D are isotopes of iron. …… [2] * 0000800000005 * DFD 5 (c) Iron can form two different ions, Fe2+ and Fe3+. (i) Complete Table 2.2 to show the number of protons, neutrons and electrons in the two iron ions shown. Table 2.2 54Fe2+ 58Fe3+ protons neutrons electrons [3] (ii) Describe a test for aqueous Fe2+ ions. test …… observations …… [2] (d) An oxidising agent converts Fe2+ ions to Fe3+ ions. (i) Define the term oxidising agent. …… [2] (ii) Explain why the conversion of Fe2+ ions to Fe3+ ions is described as oxidation. …… [1] (iii) The oxidising agent for the conversion of Fe2+ ions to Fe3+ ions is aqueous potassium manganate(VII). State one condition needed for the oxidation to take place. …… [1] (e) Iodide ions, I– , reduce Fe3+ ions to Fe2+ ions in aqueous solution. Suggest the identity of the other product formed in this reaction. …… [1] [Total: 19] * 0000800000006 * DFD 6

Question

A student prepares a sample of the insoluble salt barium sulfate, BaSO4. The student adds aqueous sodium sulfate, Na2SO4(aq), to aqueous barium chloride, BaCl 2(aq). The student carries out the following steps. step 1 Dissolve 0.100 moles of solid BaCl 2 in 100 cm3 of distilled water in a beaker to form BaCl 2(aq). step 2 Add an aqueous solution which contains 0.100 moles of Na2SO4(aq) to the beaker containing the BaCl 2(aq) from step 1. step 3 Stir the mixture and then filter it. step 4 Dry the solid left in the filter paper. (a) Complete the symbol equation for the reaction. Include state symbols. BaCl 2(aq) + Na2SO4(aq) BaSO4(……) + ……(……) [2] (b) Calculate the mass of solid BaCl 2 dissolved in step 1. mass = …… g [2] (c) The concentration of Na2SO4(aq) in step 2 is 1.25 mol / dm3. Calculate the volume, in cm3, of 1.25 mol / dm3 Na2SO4(aq) added in step 2 which contains 0.100 moles of Na2SO4 . volume = …… cm3 [1] (d) State the colour of the solid formed in step 2. …… [1] (e) The mixture is filtered in step 3. State the general term given to a solid left in the filter paper after filtration. …… [1] * 0000800000007 * DFD 7 (f) The actual mass of dry BaSO4 collected in step 4 is greater than the expected mass. This is because the student should do an additional step between step 3 and step 4. Suggest what the student should do in this additional step, and explain why the actual mass collected is greater than the expected mass. …… [2] (g) State the name of this method of salt preparation. …… [1] (h) State the name of a different: • barium salt that can be used in place of BaCl 2 …… • sulfate salt that can be used in place of Na2SO4 …… • barium salt that can be made by this method. …… [3] [Total: 13] * 0000800000008 * DFD 8

Question

Nitric acid, HNO3 , and sulfuric acid, H2SO4 , are strong acids. Ethanoic acid, CH3COOH, is a weak acid. (a) One mole of each acid is added separately to 1000 cm3 of distilled water to form a dilute solution. All three acids dissociate in distilled water. (i) State the formula of the common cation produced when each of the three acids dissociates in water. …… [1] (ii) Explain, in terms of dissociation, why: • nitric acid is described as a strong acid • ethanoic acid is described as a weak acid. [2] (iii) State which of the three dilute acids will have the highest pH value. …… [1] (iv) State the colour of thymolphthalein in all three dilute acids. …… [1] (v) Give the formula of the anion formed when: • sulfuric acid dissociates in water • ethanoic acid dissociates in water. [2] (vi) Name the two gaseous products formed during the electrolysis of dilute sulfuric acid using inert electrodes. …… and …… [2] (vii) Name the salt formed when calcium reacts with ethanoic acid. …… [1] * 0000800000009 * DFD 9 (b) Aluminium nitrate, Al (NO3)3 , is made when dilute nitric acid reacts with aluminium hydroxide, Al (OH)3 . (i) Al (OH)3 acts as a base in this reaction. Define the term base. …… [1] (ii) Al (OH)3 is not an alkali. State what this tells you about the solubility of Al (OH)3 . …… [1] (iii) Name one other compound which forms aluminium nitrate when added to dilute nitric acid. …… [1] (iv) The oxidation number of the O atoms in Al (NO3)3 is –2. The formula of the aluminium ion in Al (NO3)3 is Al 3+. Determine the oxidation number of the N atoms in Al (NO3)3. Show your working. oxidation number of N = …… [2] [Total: 15] * 0000800000010 * DFD 10

Question

This question is about the homologous series of alkanes. Three general characteristics of alkanes are: • they are generally unreactive because they do not have a functional group • they show trends in their physical properties, such as melting points and boiling points • they have similar chemical properties. (a) Describe two other general characteristics of the homologous series of alkanes. 1 …… 2 …… [2] (b) (i) State the trend in the boiling points of the alkanes as the carbon chain length increases. …… [1] (ii) Name one other physical property of alkanes that shows a trend, other than melting points and boiling points. Describe this trend as the carbon chain length of alkanes increases. name …… description …… [2] (c) State why alkanes are described as saturated. …… [1] * 0000800000011 * DFD 11 (d) Propane has the structural formula CH3CH2CH3 . When propane undergoes a monosubstitution reaction with chlorine at room temperature, two organic products can be formed. (i) State one condition needed for this substitution reaction to take place. …… [1] (ii) Give the structural formula and state the name of each organic product formed. • structural formula of product 1 name of product 1 …… • structural formula of product 2 name of product 2 …… [4] (iii) The two products formed are structural isomers of each other. Define the term structural isomers. …… [1] [Total: 12] * 0000800000012 * DFD 12

Question

Compound E shown in Fig. 6.1 is an ester. O CH3 CH2 CH2 C O CH2 CH3 Fig. 6.1 (a) On Fig. 6.1, draw a circle around all the atoms which make up the ester linkage. [1] (b) Name compound E. …… [1] (c) Deduce the empirical formula of compound E. …… [1] (d) Compound E is produced when two different compounds react together in the presence of a catalyst. (i) Name the two compounds that react together to produce compound E. 1 …… 2 …… [2] (ii) Suggest a suitable catalyst for this reaction. …… [1] (e) Determine the number of unbranched esters which have the molecular formula C5H10O2 . …… [1] (f) All unbranched esters with the molecular formula C5H10O2 combust completely to form carbon dioxide and water only. Write the symbol equation for the complete combustion of C5H10O2 . …… [1] [Total: 8] DFD 13 DFD 14 * 0000800000015 * DFD 15 The Periodic Table of Elements Group I II III IV V VI VII VIII 1 2 H He hydrogen helium Key 1 4 3 4 atomic number 5 6 7 8 9 10 Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon 7 9 relative atomic mass 11 12 14 16 19 20 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon 23 24 27 28 31 32 35.5 40 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 DFD K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton 39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon 16 85 88 89 91 93 96 – 101 103 106 108 112 115 119 122 128 127 131 55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 lanthanoids Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon 133 137 178 181 184 186 190 192 195 197 201 204 207 209 – – – 87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson – – – – – – – – – – – – – – – – – 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium 139 140 141 144 – 150 152 157 159 163 165 167 169 173 175 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium – 232 231 238 – – – – – – – – – – – The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).