Chemistry 0620/31 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 Ne Mg Al Si S Cl K Ti Fe Cu Zn I 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) forms an ion which produces a red colour in a flame test …… [1] (b) is present in diamond …… [1] (c) forms an ion with a charge of 2– …… [1] (d) is extracted from bauxite …… [1] (e) is used in electrical wiring because of its good electrical conductivity and ductility. …… [1] [Total: 5] * 0000800000003 * DFD 3

Question

The symbol for an atom of argon is shown. 40 Ar 18 (a) Complete Table 2.1 to show the number of protons and neutrons in one atom of 40 18 Ar. Table 2.1 number of protons number of neutrons [2] (b) Argon is an unreactive monatomic element. (i) Explain what is meant by the term monatomic. …… [1] (ii) Explain why argon is unreactive. Give your answer in terms of electronic configuration. …… [1] (c) At room temperature and pressure, argon is a gas. A sample of argon 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 argon when: • the temperature of the argon is increased • the pressure of the argon is increased. Use the words increases, decreases or no change in your answer. Table 2.2 change effect on the volume of argon temperature is increased pressure is increased [2] [Total: 6] * 0000800000004 * DFD 4

Question

(a) Table 3.1 shows the masses of ions, in mg, present in a 1000 cm3 sample of river water. Table 3.1 mass of ion in 1000 cm3 name of ion formula of ion of river water / mg ammonium NH4+ 0.5 bromide Br – 0.2 calcium Ca2+ 1.4 hydrogencarbonate HCO3– 6.0 iodide I– 3.2 lithium Li+ 4.3 nitrate NO3– 9.5 phosphate PO43– 0.7 sodium Na+ 8.3 sulfate 0.9 Answer these questions using the information from Table 3.1. (i) Name the positive ion that has the highest concentration. …… [1] (ii) State the formula of the sulfate ion. …… [1] (iii) Describe a test to identify the presence of iodide ions, I–, in a sample of water. test …… observations …… [2] (iv) Calculate the mass of nitrate ions, NO3– , in 200 cm3 of river water. mass = …… mg [1] * 0000800000005 * DFD 5 (b) Give the formulae of two ions from Table 3.1 which can be combined with potassium ions to make an NPK fertiliser. …… and …… [1] (c) Name two ions from Table 3.1 which lead to deoxygenation of water and damage to aquatic life. …… and …… [2] (d) The diagram in Fig. 3.1 shows the apparatus used to separate pure water from the sample of river water. river water pure water heat Fig. 3.1 Name the separation method shown in Fig. 3.1. …… [1] [Total: 9] * 0000800000006 * DFD 6

Question

(a) Molecules of compound C are produced by some plants. Fig. 4.1 shows the displayed formula of a molecule of compound C. O H H H C H H C H O H H C C C C C C H H H C C H H H H H Fig. 4.1 Deduce the molecular formula of compound C to show the number of atoms of carbon, hydrogen and oxygen. …… [1] (b) On Fig. 4.1, draw a circle around the part of the molecule which shows that the molecule is unsaturated. [1] (c) A different molecule found in plants has the molecular formula C11H14O3. Complete Table 4.1 to calculate the relative molecular mass of C11H14O3. Table 4.1 relative type of atom number of atoms atomic mass carbon 11 12 11 × 12 = 132 hydrogen 1 oxygen 16 relative molecular mass = …… [2] (d) Petroleum is a mixture of hydrocarbons which can be separated into groups of compounds called fractions. Explain what is meant by the term hydrocarbon. …… [1] * 0000800000007 * DFD 7 (e) 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 lowest boiling point …… [1] (ii) have the highest viscosity …… [1] (iii) are used for jet fuel. …… [1] * 0000800000008 * DFD 8 (f) Table 4.2 shows some properties of compounds found in the naphtha fraction. Table 4.2 molecular melting point boiling point name formula / °C / °C heptane –90 98 octane C8H18 125 nonane C9H20 –54 150 decane C10H22 –30 174 undecane C11H24 –25 195 (i) A molecule of heptane contains seven carbon atoms. Deduce the molecular formula of heptane. …… [1] (ii) Use the information in Table 4.2 to predict the melting point of octane, C8H18 . …… [1] (g) When heated strongly in the presence of a catalyst, decane reacts to form smaller molecules. (i) Name this type of endothermic reaction. …… [1] (ii) Ethene is one of the molecules formed when decane is heated strongly in the presence of a catalyst. Draw the displayed formula of ethene. Show all the atoms and all the bonds. [2] * 0000800000009 * DFD 9 (h) Ethene is polymerised to form the plastic poly(ethene). (i) Name this type of polymerisation. …… [1] (ii) Describe two environmental challenges caused by the disposal of plastics such as poly(ethene). 1 …… 2 …… [2] [Total: 16] * 0000800000010 * DFD 10

Question

This question is about elements in Group I and in Group VII of the Periodic Table and their compounds. (a) Chlorine is in Group VII of the Periodic Table. Give the colour and state of chlorine at room temperature and pressure. colour …… state …… [2] (b) State the use of chlorine in the treatment of the domestic water supply. …… [1] (c) Iodine is in Group VII of the Periodic Table. Table 5.1 shows the melting point and the boiling point of iodine. Table 5.1 melting point / °C 114 boiling point / °C 184 Use the information in Table 5.1 to deduce the physical state of iodine at 195 °C. Give a reason for your answer. physical state …… reason …… [2] (d) Potassium is an element in Group I of the Periodic Table. Elements in Group I have a low density and relatively low melting and boiling points. State one other physical property of potassium. …… [1] * 0000800000011 * DFD 11 (e) When a sample of potassium is added to a large container of cold water, a chemical reaction occurs. (i) Describe what is observed when potassium is added to water. …… [3] (ii) The word equation for the reaction of potassium with water is shown. potassium + water potassium hydroxide + hydrogen Describe a test for hydrogen. test …… observations …… [1] (f) Potassium reacts with oxygen to form potassium oxide, K2O. Complete the symbol equation for this reaction. …… K + …… 2K2O [2] (g) Solid potassium oxide, K2O, dissolves in water to form an alkali. Choose the pH value of the solution formed when solid potassium oxide is dissolved in water. Draw a circle around your chosen answer. pH 1 pH 5 pH 7 pH 12 [1] * 0000800000012 * DFD 12 (h) Potassium reacts with chlorine to form the ionic compound potassium chloride. Complete the dot-and-cross diagram in Fig. 5.1 for potassium chloride to show: • the electronic configuration for each ion • the charge on each ion. K Cl Fig. 5.1 [3] [Total: 16] * 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 (coke) and calcium carbonate in a blast furnace. (i) Give two reasons why carbon is used in a blast furnace. 1 …… 2 …… [2] (ii) Slag is a waste product of this extraction. Describe how slag is produced. …… [2] (iii) Iron ore contains iron(III) oxide. The equation for the extraction of iron from iron(III) oxide is shown. Fe2O3 + 3CO 2Fe + 3CO2 Explain how this equation shows that carbon monoxide is oxidised. …… [1] (b) Pure iron is less useful than its alloys such as stainless steel. (i) Name two metals most commonly used in stainless steel, other than iron. 1 …… 2 …… [2] (ii) State one use of stainless steel. …… [1] * 0000800000015 * DFD 15 (c) Table 6.1 shows the observations when four different metals are added separately to dilute ethanoic acid. Table 6.1 metal observations a few bubbles of gas given off slowly and zinc the temperature of the mixture increases very slowly no bubbles of gas given off and titanium no temperature increase of the mixture many bubbles of gas given off very quickly and calcium the temperature of the mixture increases rapidly bubbles of gas given off quickly and magnesium the temperature of the mixture increases slowly (i) Put the four metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive [2] (ii) Complete the word equation for the reaction of calcium with ethanoic acid. ethanoic …… calcium + + …… acid [2] [Total: 12] * 0000800000016 * DFD 16

Question

Fig. 7.1 shows the apparatus used to electrolyse dilute sulfuric acid using inert electrodes. + power – supply dilute sulfuric acid Fig. 7.1 (a) State what is meant by the term electrolysis. …… [2] (b) Label the cathode in Fig. 7.1. [1] (c) Name one product formed at the anode. …… [1] (d) The inert electrodes used are made of graphite. (i) Explain what is meant by the term inert. …… [1] (ii) State one other use for graphite. …… [1] * 0000800000017 * DFD 17 (e) Excess solid copper(II) carbonate is added to dilute sulfuric acid. Aqueous copper(II) sulfate, water and carbon dioxide gas are produced. (i) State with a reason if this is a chemical or a physical change. …… [1] (ii) Name a method to remove the excess copper(II) carbonate from the mixture. …… [1] (iii) Name one other substance which can be added to dilute sulfuric acid to form aqueous copper(II) sulfate. …… [1] (f) Copper(II) sulfate, CuSO4, exists in different forms. Draw one line from each form of copper(II) sulfate to its description. form of copper(II) sulfate description solid CuSO4 chemically aqueous CuSO4 combined with water CuSO4 dissolved hydrated CuSO4 in water solid CuSO4 containing anhydrous CuSO4 no water [2] [Total: 11] * 0000800000018 * DFD 18

Question

A student investigates the reaction of small pieces of magnesium with excess dilute hydrochloric acid. Mg + 2HCl MgCl 2 + H2 Fig. 8.1 shows the total volume of hydrogen gas, H2, produced as the reaction proceeds. 300 250 200 total volume 150 of H2 / cm3 100 50 0 0 20 40 60 80 100 120 140 160 time / s Fig. 8.1 (a) Use Fig. 8.1 to deduce the time taken for the reaction to finish. time taken for reaction to finish = …… s [1] (b) The reaction is repeated using larger pieces of magnesium of the same total mass. 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 H2 produced when the reaction is complete. [1] * 0000800000019 * DFD 19 (c) Fig. 8.2 shows the reaction pathway diagram for the reaction of magnesium with dilute hydrochloric acid. energy Mg + 2HCl MgCl2 + H2 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: 5] 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 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr DFD 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 85 88 89 91 93 96 – 101 103 106 108 112 115 119 122 128 127 131 20 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.).