Chemistry 0620/33 October/November 2025: question paper and mark scheme

Question

Fig. 1.1 shows part of the Periodic Table. I II III IV V VI VII VIII H He Li C N O Ne Na Al S Ca Fe Zn Br I Au Fig. 1.1 Answer the following questions using only the symbols of the elements in Fig. 1.1. Each symbol may be used once, more than once or not at all. Give the symbol of the element that: (a) is used in food containers because of its resistance to corrosion …… [1] (b) is a metal that does not react with water, dilute acids or oxygen …… [1] (c) reacts with hydrogen in a fuel cell …… [1] (d) is bonded to hydrogen in methane. …… [1] [Total: 4] * 0000800000003 * DFD 3

Question

The symbol for an atom of xenon is shown. 131 Xe 54 (a) Complete Table 2.1 to show the number of neutrons and nucleons in one atom of 131 54 Xe. Table 2.1 number of neutrons number of nucleons [2] (b) Xenon is a gas at room temperature and pressure. A sample of xenon is placed in a sealed syringe with a freely moving plunger. Complete Table 2.2 to show the effect, if any, on the volume of xenon when: • the temperature of the xenon is decreased • the pressure of the xenon is decreased. Use the words increases, decreases or no change in your answer. Table 2.2 change effect on the volume of xenon temperature is decreased pressure is decreased [2] (c) When xenon is cooled, it becomes a solid. Describe the arrangement and motion of the particles in solid xenon. particle arrangement …… particle motion …… [2] [Total: 6] * 0000800000004 * DFD 4

Question

(a) Table 3.1 shows the masses of ions, in mg, present in a 600 cm3 sample of contaminated water. Table 3.1 mass of ion in 600 cm3 name of ion formula of ion of contaminated water / mg calcium Ca2+ 7.3 HCO3– hydrogencarbonate 11.2 iodide I– 25.0 magnesium Mg2+ 6.2 nitrate NO3– 0.3 PO43 – 0.1 potassium K+ 0.1 sodium Na+ 2.7 sulfate SO42– 9.0 Answer these questions using the information from Table 3.1. (i) Name the positive ion that has the highest concentration. …… [1] (ii) State the name of the PO43 – ion. …… [1] (iii) Describe a test to identify the presence of nitrate ions, NO3– , in a sample of water. test …… test result …… [2] (iv) Calculate the mass of sodium ions, Na+, in 200 cm3 of the contaminated water. mass = …… mg [1] (v) A higher concentration of nitrate ions in river water can cause deoxygenation. State a source of a higher concentration of nitrate ions in river water. …… [1] * 0000800000005 * DFD 5 (b) A sample of water is taken from a river. The sample contains some insoluble substances. State one method of removing the insoluble substances from the water. …… [1] (c) (i) The water contains harmful microbes. Suggest a source of the microbes in the water. …… [1] (ii) State how the water is treated so that the microbes do not cause harm to people. …… [1] (d) Before the treatment in (c)(ii), the water has a bad taste and odour. State the name of a substance that is added to remove the bad taste and odour from the water. …… [1] [Total: 10] * 0000800000006 * DFD 6

Question

(a) Compound B is a molecule found in a plant called basil. Fig. 4.1 shows the displayed formula of a molecule of compound B. H H H C C H H H H C O C C C C C H C C H H H H Fig. 4.1 Deduce the molecular formula of compound B to show the number of atoms of carbon, hydrogen and oxygen. …… [1] (b) On Fig. 4.1, draw a circle around one part of the molecule which shows that the molecule is unsaturated. [1] (c) A different molecule found in plants has the molecular formula C9H10O3. Complete Table 4.1 to calculate the relative molecular mass of C9H10O3. Table 4.1 relative type of atom number of atoms atomic mass carbon 9 12 9 × 12 = 108 hydrogen 1 oxygen 16 relative molecular mass = …… [2] * 0000800000007 * DFD 7 (d) Fig. 4.2 shows the names of some of the fractions obtained from petroleum using a fractionating column. gasoline / petrol naphtha kerosene / paraffin diesel oil / gas oil fuel oil lubricating oil petroleum Fig. 4.2 Using only the fractions shown in Fig. 4.2, name the fraction which contains compounds that: (i) have the highest boiling point …… [1] (ii) have the shortest chain length …… [1] (iii) are used to make waxes and polishes. …… [1] * 0000800000008 * DFD 8 (e) Table 4.2 shows some properties of alcohols. Table 4.2 melting point boiling point name formula / °C / °C hexanol C6H13OH – 45 157 heptanol C7H15OH –35 176 octanol –16 195 nonanol C9H19OH 214 decanol C10H21OH 7 233 (i) The compounds in Table 4.2 are members of the alcohol homologous series. State what is meant by the term homologous series. …… [1] (ii) A molecule of octanol has eight carbon atoms. Use the information in Table 4.2 to deduce the formula of octanol. …… [1] (iii) Use the information in Table 4.2 to predict the melting point of nonanol. …… [1] (f) (i) Hexanol is a fuel. In excess oxygen, hexanol undergoes complete combustion to produce water and one other product. Identify this other product. …… [1] (ii) State the colour change observed when water is added to anhydrous copper(II) sulfate. from white to …… [1] * 0000800000009 * DFD 9 (g) Ethanol can be manufactured by fermentation. Name the reactant, and state two conditions needed for the fermentation of ethanol. reactant …… condition 1 …… condition 2 …… [3] (h) Ethanol can be converted into ethanoic acid. Draw the displayed formula of ethanoic acid. Show all the atoms and all the bonds. [2] [Total: 17] * 0000800000010 * DFD 10

Question

This question is about elements in different groups of the Periodic Table and their compounds. (a) Silicon is in Group IV of the Periodic Table. Explain why silicon is placed in Group IV. Give your answer in terms of electronic configuration. …… [1] (b) Tin is also in Group IV of the Periodic Table. Table 5.1 shows the melting point and the boiling point of tin. Table 5.1 melting point / °C 232 boiling point / °C 2602 Use Table 5.1 to deduce the physical state of tin at 175 °C. Give a reason for your answer. physical state …… reason …… [2] (c) Iodine is in Group VII of the Periodic Table. Give the colour and state of iodine at room temperature and pressure. colour …… state …… [2] * 0000800000011 * DFD 11 (d) When a sample of calcium is added to a large container of cold water, a chemical reaction occurs. (i) Describe what is observed when calcium is added to water. …… [2] (ii) Complete the word equation for the reaction of calcium with water. calcium + water + …… [2] (e) Dilute nitric acid is poured into a conical flask. (i) Choose the pH value of dilute nitric acid. Draw a circle around your chosen answer. pH 1 pH 7 pH 9 pH 13 [1] (ii) Complete the equation for the neutralisation of an acid to produce water. State symbols are not required. H+ + …… H2O [1] (iii) A few drops of methyl orange indicator are added to the flask containing dilute nitric acid. Solid lithium carbonate is slowly added to the flask until the indicator changes colour. State the colour change of the methyl orange indicator as the lithium carbonate is added to the dilute nitric acid in the flask. from …… to …… [2] * 0000800000012 * DFD 12 (f) Lithium carbonate reacts with dilute nitric acid to form aqueous lithium nitrate. Describe a test to show that Li+ ions are present in the solution. test …… observations …… [2] (g) Chlorine is in Group VII of the Periodic Table. Chlorine reacts with lithium to form the ionic compound lithium chloride. Complete the dot-and-cross diagram in Fig. 5.1 for lithium chloride to show: • the electronic configuration for each ion • the charge on each ion. Use crosses to represent the electrons of lithium. Li Cl Fig. 5.1 [3] [Total: 18] * 0000800000013 * DFD 13 Question 6 starts on the next page. * 0000800000014 * DFD 14

Question

This question is about metals. (a) Iron is extracted from its ore using carbon in a blast furnace. When calcium carbonate is heated strongly in the blast furnace, it forms calcium oxide and carbon dioxide. CaCO3 CaO + CO2 (i) State the type of reaction that occurs when calcium carbonate is heated strongly. …… [1] (ii) State whether calcium oxide is an acidic oxide or a basic oxide. Explain your answer. …… [1] (iii) Name the gas removed by calcium oxide in flue gas desulfurisation. …… [1] (b) Zinc is also extracted from its ore using carbon. (i) The equation for the extraction of zinc from zinc oxide is shown. 2ZnO + C 2Zn + CO2 Explain how this equation shows that zinc oxide is reduced. …… [1] (ii) Brass is an alloy that contains zinc. Name the other metal in brass. …… [1] (iii) Suggest two reasons why brass is used to make water taps rather than pure zinc. 1 …… 2 …… [2] * 0000800000015 * DFD 15 (c) The extraction of zinc from its ore produces atmospheric sulfur dioxide and carbon dioxide. (i) State the adverse effect that increased levels of sulfur dioxide have on the environment. …… [1] (ii) Increased levels of carbon dioxide in the atmosphere can lead to increased global warming. State one strategy which would help to remove carbon dioxide that is already in the atmosphere. …… [1] (d) Table 6.1 shows the observations when four different metals are added separately to dilute hydrochloric acid. Table 6.1 metal observations a few bubbles of gas given off very slowly and Fe the temperature of the mixture increases very slowly no bubbles of gas given off and W no temperature increase of the mixture many bubbles of gas given off very quickly and Ba the temperature of the mixture increases rapidly bubbles of gas given off quickly and Mg the temperature of the mixture increases slowly Put the four metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive [2] [Total: 11] * 0000800000016 * DFD 16

Question

Fig. 7.1 shows the apparatus used to electroplate a nickel object with copper. power supply aqueous electrolyte nickel object Fig. 7.1 (a) Label the anode in Fig. 7.1. [1] (b) Name a suitable aqueous electrolyte for the electroplating in Fig. 7.1. …… [1] (c) Fig. 7.2 shows the apparatus used to electrolyse molten lead(II) bromide using inert electrodes. power supply crucible molten lead(II) bromide Fig. 7.2 State the colour of the gas produced at the anode in this electrolysis. …… [1] (d) State whether the electrolysis of molten lead(II) bromide produces a physical or chemical change. Explain your answer. type of change …… explanation …… [1] * 0000800000017 * DFD 17 (e) Cobalt is a metal that reacts slowly with a dilute acid to produce cobalt(II) ethanoate and hydrogen. (i) Name the dilute acid. …… [1] (ii) Describe a test for hydrogen. test …… observations …… [1] (f) Cobalt(II) chloride, CoCl 2, exists in different forms. Draw one line from each form of cobalt(II) chloride to its description. form of cobalt(II) chloride description solid CoCl 2 hydrated CoCl 2 containing no water solid CoCl 2 chemically aqueous CoCl 2 combined with water anhydrous CoCl 2 CoCl 2 dissolved in water [2] [Total: 8] * 0000800000018 * DFD 18

Question

Excess dilute citric acid, C6H8O7, is added to aqueous sodium hydrogencarbonate to form aqueous sodium citrate, Na3C6H5O7, carbon dioxide and water. C6H8O7(aq) + 3NaHCO3(aq) Na3C6H5O7(aq) + 3CO2(g) + 3H2O(l) (a) Give the meaning of the symbol (l) in the equation. …… [1] (b) Fig. 8.1 shows the total volume of carbon dioxide gas, CO2, produced as the reaction proceeds. 125 100 total volume 75 of CO2 / cm3 50 25 0 0 20 40 60 80 100 120 140 time / s Fig. 8.1 Use Fig. 8.1 to determine the total volume of CO2 produced at 24 s. total volume of CO2 at 24 s = ……cm3 [1] * 0000800000019 * DFD 19 (c) The reaction is repeated using excess citric acid of a lower concentration. All other conditions stay the same. State the effect, if any, on: (i) the time taken for the reaction to finish …… [1] (ii) the total volume of CO2 produced when the reaction is complete. …… [1] (d) Fig. 8.2 shows the reaction pathway diagram for the reaction of dilute citric acid with aqueous sodium hydrogencarbonate. Na3C6H5O7 + 3CO2 + 3H2O energy C6H8O7 + 3NaHCO3 progress of reaction Fig. 8.2 Deduce the type of energy change shown in the diagram in Fig. 8.2. Explain your answer. …… [2] [Total: 6] 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 20 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.).