Chemistry 0620/33 May/June 2025: question paper and mark scheme

Question

A list of substances is shown. calcium calcium oxide carbon carbon dioxide chlorine copper gold iodine neon nitrogen oxygen potassium sulfur dioxide Answer the following questions about these substances. Each substance may be used once, more than once or not at all. State which substance is: (a) an element which forms an ion with a 3– charge …… [1] (b) a transition element …… [1] (c) a gas that is identified using limewater …… [1] (d) approximately 78% of clean, dry air …… [1] (e) used in electrical wiring …… [1] (f) the least reactive metal in the list …… [1] (g) a diatomic molecule which is a solid at room temperature and pressure …… [1] (h) a compound that reacts with impurities in the blast furnace to form slag …… [1] (i) an element with a relative atomic mass of 12. …… [1] [Total: 9]

Question

This question is about sea water and the substances found in sea water. (a) Table 2.1 shows the masses of the compounds present when a 2000 cm3 sample of sea water is evaporated. Table 2.1 compound formula mass of compound / g sodium chloride NaCl 28.0 MgSO4 5.5 potassium chloride KCl 2.5 calcium carbonate CaCO3 2.0 Answer these questions using the information from Table 2.1. (i) State the chemical name of MgSO4. …… [1] (ii) The total mass of compounds formed from 2000 cm3 of sea water is 38.0 g. Calculate the total mass of compounds present in 800 cm3 of sea water. mass = …… g [1] (iii) Potassium chloride is soluble in water. Choose one other compound that is soluble in water. Tick (✓) one box. lead(II) sulfate magnesium carbonate silver chloride sodium hydroxide [1] (b) Potassium iodide is also found in sea water and contains iodide ions. Describe a test for iodide ions. test …… observations …… [2] (c) Potassium chloride contains potassium ions. Complete Fig. 2.1 to show: • the electronic configuration of a potassium ion • the charge on the ion. K Fig. 2.1 [2] (d) Sodium chloride is a solid at room temperature. Describe the separation and motion of the particles in a solid. separation …… motion …… [2] (e) Sea water contains dissolved phosphate ions. State one source of phosphate ions. …… [1] (f) Water is a simple molecular compound. Complete the dot-and-cross diagram in Fig. 2.2 for a molecule of water. Show outer electrons only. O H H Fig. 2.2 [2] [Total: 12]

Question

This question is about organic chemistry. (a) Petroleum is a mixture of hydrocarbons and is separated by fractional distillation in an industrial process. (i) State which physical property of hydrocarbons allows them to be separated by fractional distillation. …… [1] (ii) Describe how petroleum is separated into fractions by fractional distillation. …… [2] (iii) Name the process that breaks down long chain hydrocarbon molecules to form short chain hydrocarbon molecules. …… [1] (iv) Some of the fractions obtained from petroleum are shown. Draw a line from each fraction to its use. fraction use bitumen waxes and polishes lubricating oil making roads chemical naphtha feedstock [2] (b) Ethanoic acid is an organic molecule. (i) Draw the displayed formula of a molecule of ethanoic acid. [2] (ii) Ethanoic acid reacts with sodium carbonate. Name the salt produced in this reaction. …… [1] (c) Ethane is burned in excess oxygen. Name the two products of this process. …… and …… [2] (d) Ethanol is another organic molecule. State two ways to manufacture ethanol. 1 …… 2 …… [2] (e) Fig. 3.1 shows the displayed formula of an organic molecule. H H H H H O H O H C C C C C C C O H H O H H H Fig. 3.1 (i) Deduce the molecular formula of the molecule in Fig. 3.1. …… [1] (ii) Explain why the molecule in Fig. 3.1 is unsaturated. …… [1] [Total: 15]

Question

This question is about nitrogen and its compounds. (a) (i) Explain why nitrogen is in Group V of the Periodic Table. …… [1] (ii) Two isotopes of nitrogen are shown in Fig. 4.1. 14N 15N 7 7 Fig. 4.1 Complete Table 4.1 to show the number of protons, neutrons and electrons in one atom of these isotopes. Table 4.1 protons neutrons electrons 14N 7 15N 7 [3] (b) Oxides of nitrogen are air pollutants. (i) State one source of oxides of nitrogen in the air. …… [1] (ii) Ammonia reacts with oxygen to form nitrogen dioxide and water. Complete the symbol equation for this reaction. 4NH3 + 7O2 4NO2 + ……H2O [1] (iii) State the type of bonding between the atoms in nitrogen dioxide. …… [1] (iv) State whether nitrogen dioxide is an acidic or basic oxide. Give a reason for your answer. …… [1] (c) A compound of nitrogen has the formula Al (NO3)3. Complete Table 4.2 to calculate the relative formula mass of Al (NO3)3. Table 4.2 atom number of atoms relative atomic mass oxygen 9 16 9 × 16 = 144 aluminium 27 nitrogen 14 relative formula mass = …… [2] [Total: 10]

Question

This question is about ionic compounds and simple molecular compounds. (a) Complete the word equation to show the reaction between copper(II) carbonate and nitric acid. copper(II) …… …… + nitric acid + + carbonate [3] (b) Aqueous magnesium chloride is prepared by adding excess magnesium oxide powder to dilute hydrochloric acid. Describe how to prepare a sample of pure, dry magnesium chloride crystals after the reaction is complete. In your answer describe how to: • remove the excess magnesium oxide from the reaction mixture • crystallise the magnesium chloride • dry the crystals. …… [3] (c) Fig. 5.1 shows the apparatus for the electrolysis of molten cobalt(II) bromide using inert electrodes. – power + supply heat Fig. 5.1 (i) Label Fig. 5.1 to show the: • anode • electrolyte. [2] (ii) Name the products formed at the positive and negative electrodes. positive electrode …… negative electrode …… [2] (d) Table 5.1 shows some properties of five compounds, A, B, C, D and E. Table 5.1 electrical conductivity compound density in g / cm3 melting point in °C when molten A conducts 1.85 115 B does not conduct 2.65 1713 C does not conduct 0.42 –182 D conducts 2.99 1190 E does not conduct 1.56 –101 State which two of the compounds, A, B, C, D and E, are simple molecules. Give two reasons for your answer. compounds …… and …… reason 1 …… reason 2 …… [3] [Total: 13]

Question

This question is about chemical reactions and their energy changes. (a) Tick (✓) one box that shows a chemical change. boiling ethanol decomposing vegetation dissolving salt mixing ink and water [1] (b) Table 6.1 shows the results of four experiments. Table 6.1 experiment initial temperature / °C final temperature / °C 1 20 14 2 18 26 3 19 25 4 17 12 (i) State which experiment shows the greatest temperature change. …… [1] (ii) State which experiment is the most endothermic. …… [1] (iii) Fig. 6.1 shows an incomplete reaction pathway diagram for an exothermic reaction. progress of reaction Fig. 6.1 Complete Fig. 6.1 by labelling: • the vertical axis • the reactants • the products. [2] [Total: 5]

Question

This question is about air and water. (a) Water needs to be treated to make it safe to drink. Complete Fig. 7.1 to show the three stages needed in the treatment of domestic water. The second stage has been completed. impure addition of drinking water carbon water Fig. 7.1 [2] (b) Describe a chemical test for the presence of water. test …… observations …… [2] (c) A sample of air contains carbon dioxide and oxides of nitrogen. State one harmful effect of each of these air pollutants. carbon dioxide …… oxides of nitrogen …… [2] [Total: 6]

Question

This question is about metals. (a) (i) A student investigates the reaction of four different metals, A, B, C and D, with dilute sulfuric acid. All other conditions are the same. The results of the experiments are shown in Table 8.1. Table 8.1 metal observations A lots of bubbles at room temperature B no bubbles C few bubbles on warming D lots of bubbles on warming Put the metals, A, B, C and D, in order of their reactivity. most reactive …… least reactive …… [1] (ii) Increasing the temperature of the acid increases the rate of reaction. State two other ways to increase the rate of this reaction. 1 …… 2 …… [2] (b) In another experiment, a student adds lithium to water. An alkaline solution is formed. (i) State the colour seen in the flame test for lithium ions. …… [1] (ii) State the ion that all aqueous alkalis contain. …… [1] (iii) State the colour of thymolphthalein in an aqueous alkali. …… [1] (c) Pewter is an alloy that contains tin. (i) State which one of these diagrams, A, B, C or D, best represents an alloy. A B C D …… [1] (ii) Suggest one property of pewter that makes it more useful than pure tin. …… [1] (d) Metals are good thermal conductors. Describe two other physical properties that are typical of metals. 1 …… 2 …… [2] [Total: 10] 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 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.).