Chemistry 0620/21 October/November 2025: question paper and mark scheme

Question

A sealed balloon contains air. The temperature of the balloon is increased. Which row describes how the pressure in the balloon and the kinetic energy of the particles in air change? kinetic energy pressure of particles A decreases decreases B increases decreases C decreases increases D increases increases

Question

Ammonia gas is reacted with hydrogen chloride gas using the apparatus shown. Solid ammonium chloride is produced. long glass tube solid ammonium chloride cotton wool soaked cotton wool soaked in in aqueous ammonia aqueous hydrogen chloride Which statement explains why the solid ammonium chloride is formed nearer to the hydrogen chloride? A Aqueous ammonia is a base and aqueous hydrogen chloride is an acid. B Ammonia molecules diffuse more slowly than hydrogen chloride molecules. C Hydrogen chloride has a greater molecular mass than ammonia. D Only ammonia molecules diffuse in all directions at the same time.

Question

The table shows information about four different particles. nucleon number number number particle number of protons of neutrons of electrons Na 23 11 W 11 Na+ 23 11 12 X O 16 8 Y 8 O2– 16 8 8 Z What are the values of W, X, Y and Z? W X Y Z A 11 10 10 8 B 11 11 8 10 C 12 10 8 10 D 12 11 10 8

Question

Substances with giant covalent structures can be used as lubricants and as cutting tools for hard materials. The diagrams show how the atoms are arranged in two giant covalent substances, P and Q. key strong covalent bond weak attraction P Q Which statement is correct? A Only P is used as a cutting tool and only Q is used as a lubricant. B Only P is used as a lubricant and only Q is used as a cutting tool. C P and Q are both used as cutting tools. D P and Q are both used as lubricants.

Question

Symbols representing four particles are shown. 40 41 2+ 37 37 20 W 20 X 18 Y 17 Z The letters are not the chemical symbols. Which particles have the same number of neutrons? A W and X2+ B W and Z C X2+ and Y D Y and Z

Question

Which statement describes the formation of bonds in lithium bromide? A A lithium atom donates one electron to a bromine atom. B A bromine atom donates one electron to a lithium atom. C A lithium atom shares a pair of electrons with a bromine atom. D A bromine atom donates a pair of electrons to a lithium atom.

Question

Which statement explains why solid magnesium is a good conductor of electricity? A Magnesium has delocalised electrons that can move through the lattice. B Magnesium has strong attractions between ions. C Magnesium consists of a giant lattice of anions in a ‘sea’ of delocalised electrons. D Magnesium consists of metal ions that move through the lattice.

Question

The equation for the reaction between dilute ethanoic acid and aqueous lithium hydroxide is shown. CH3COOH + LiOH → CH3COOLi + H2O In an experiment, 20.0 cm3 of 0.050 mol / dm3 aqueous lithium hydroxide is exactly neutralised by 12.5 cm3 of dilute ethanoic acid. Which statement is correct? 1000 A The amount of lithium hydroxide is equal to 0.050 × mol. 20 B The amount of ethanoic acid reacted is 0.0010 mol. C The concentration of the dilute ethanoic acid is 0.16 mol / dm3. D The volume of aqueous lithium hydroxide used is 0.20 dm3.

Question

The molecular formulae of four compounds are listed. 1 CH4 2 C2H6 3 C3H8 4 C3H6 Which molecular formulae are also the empirical formulae for the compounds? A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

Question

The equation for the reaction between copper(II) oxide, CuO, and ammonia is given. 3CuO + 2NH3 → 3Cu + 3H2O + N2 [Mr: CuO, 80; NH3, 17; H2O, 18; N2, 28] [Ar: Cu, 64] Which statements about this reaction are correct? 1 80.0 g of copper(II) oxide reacts exactly with 17.0 g of ammonia. 2 4.0 g of copper(II) oxide reacts with excess ammonia to produce 3.2 g of copper. 3 The mass of water produced in this reaction is greater than the mass of nitrogen. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

How many atoms are present in 1.00 mol of argon? A 2.06 × 1023 B 3.02 × 1026 C 6.02 × 1023 D 6.32 × 1020

Question

Aqueous copper(II) sulfate is electrolysed using copper electrodes. Which statement is correct? A Oxygen gas is produced at the positive electrode. B The blue colour of the solution gradually fades. C The concentration of copper ions in the solution stays the same. D The mass of the negative electrode decreases.

Question

Which row describes the reactions during the electrolysis of dilute aqueous sodium chloride? anode reaction cathode reaction A H2 → 2H+ + 2e– 2H2O + O2 + 4e– → 4OH– B 2H+ + 2e– → H2 4OH– → 2H2O + O2 + 4e– C 2H2O + O2 + 4e– → 4OH– H2 → 2H+ + 2e– D 4OH– → 2H2O + O2 + 4e– 2H+ + 2e– → H2

Question

Information about two reactions is given. ● The neutralisation reaction between citric acid and sodium hydrogencarbonate is endothermic. ● The displacement reaction between magnesium and carbon dioxide is exothermic. Which statements about the two reactions are correct? 1 The energy of the products formed in the neutralisation reaction is greater than the energy of the reactants. 2 The energy of magnesium and carbon dioxide is greater than the energy of magnesium oxide and carbon. 3 In an exothermic reaction, the energy required to break the bonds is greater than the energy released when the new bonds are formed. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

The reaction pathway diagram for a reaction is shown. 3 1 energy 2 progress of reaction Which row identifies the activation energy, Ea, and the enthalpy change, ΔH, for this reaction? Ea ΔH A 1 2 B 1 3 C 2 3 D 3 1

Question

Hydrogen peroxide solution decomposes very slowly at room temperature to produce oxygen gas. This gas forms a rising foam when liquid detergent is added. Five test-tubes are half-filled with hydrogen peroxide solution. A drop of liquid detergent is added to each one. Different metal oxides are added to four of the test-tubes and the height of the foam formed after one minute is measured. The results are shown. height of metal oxide foam / cm no metal oxide added 0.1 aluminium oxide 0.1 calcium oxide 0.2 copper(II) oxide 2.3 manganese(IV) oxide 5.4 Which conclusion can be drawn from these results? A Metal oxides do not affect the rate of this reaction. B All metal oxides increase the rate of this reaction and act as catalysts. C Manganese(IV) oxide is the best catalyst of the four metal oxides tested. D Only transition element oxides increase the rate of this reaction.

Question

Which equation represents one of the reactions in the Contact process? A 2SO2(g) + O2(g) 2SO3(g) B 2SO2(g) + O2(g) 2SO3(aq) C 2SO3(g) + O2(g) 2SO4(aq) D 2SO3(g) + O2(g) 2SO4(g)

Question

The ionic equation for the redox reaction between acidified manganate(VII) ions and iodide ions is shown. 2MnO4–(aq) + 16H+(aq) + 10I–(aq) → 2Mn2+(aq) + 5I2(aq) + 8H2O(l) Which row shows the changes in oxidation number for manganese and for iodine during this reaction? manganese iodine from to from to A –2 +4 –1 0 B –2 +4 –10 +5 C +7 +2 –1 0 D +7 +2 –10 +5

Question

In the Haber process, nitrogen and hydrogen react to form ammonia. N2 + 3H2 2NH3 The forward reaction is exothermic. Which changes in pressure and temperature increase the yield of ammonia? change in change in pressure temperature A decrease decrease B decrease increase C increase decrease D increase increase

Question

Which statement describes a property of ethanoic acid? A It does not produce carbon dioxide when added to sodium carbonate. B It does not produce hydrogen when added to magnesium. C It only donates some of its protons when added to excess aqueous sodium hydroxide. D It only partially dissociates when added to water.

Question

A student adds different solid salts to an excess of water. The student stirs the mixtures to determine the solubilities of the salts. The results are shown. W X Y Z What could the four different salts be? W X Y Z A calcium sulfate lead(II) chloride ammonium nitrate potassium sulfate B ammonium nitrate sodium carbonate calcium sulfate lead(II) chloride C sodium carbonate calcium sulfate potassium sulfate ammonium nitrate D lead(II) chloride ammonium nitrate sodium carbonate calcium sulfate

Question

Four metal oxides are listed. 1 Al 2O3 2 CaO 3 CuO 4 ZnO Which metal oxides are amphoteric? A 1 and 4 B 1 only C 2, 3 and 4 D 2 and 3 only

Question

The ions formed when element X and element Y react together are shown. ● Element X forms X– ions. ● Element Y forms Y2+ ions. Which row identifies the position of X and of Y in the Periodic Table? X Y A Group I Group VI B Group VII Group II C Group VII Group VI D Group I Group II

Question

Which properties decrease down the group of alkali metals? 1 melting point 2 density 3 reactivity A 1 and 2 B 1 only C 2 and 3 D 3 only

Question

Some halide ions are displaced from aqueous potassium halides by halogens. In which mixtures are the halide ions displaced? 1 potassium bromide and chlorine 2 potassium bromide and iodine 3 potassium iodide and chlorine 4 potassium chloride and iodine A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

Question

What is the correct order of reactivity of the following metals, from least reactive to most reactive? A calcium → magnesium → zinc → copper B copper → zinc → magnesium → calcium C copper → zinc → calcium → magnesium D zinc → copper → magnesium → calcium

Question

The equation for the reaction between aluminium and iron( III) oxide is shown. 2Al + Fe2O3 → Al 2O3 + 2Fe Which statement about this reaction is correct? A The aluminium acts as an oxidising agent. B It shows that iron is more reactive than aluminium. C The oxidation number of the aluminium decreases during the reaction. D It shows that aluminium has a greater tendency to form ions than iron.

Question

Which row identifies methods used to prevent iron from rusting? washing with greasing painting distilled water A key B = yes C = no D

Question

Which statement about the extraction of aluminium by electrolysis is correct? A Aluminium oxide is dissolved in molten cryolite to increase its melting point. B At the cathode, oxygen ions lose electrons to form oxygen gas. C The carbon in the graphite anode reacts with oxygen gas forming carbon dioxide. D The reaction at the anode is Al 3+ + 3e– → Al.

Question

Catalytic converters are used to remove oxides of nitrogen from exhaust gases. The equation represents one of the reactions that occur in a catalytic converter. 2NO + 2CO → N2 + 2CO2 What is a disadvantage of using a catalytic converter to remove oxides of nitrogen? A CO is an essential reactant in photosynthesis. B CO2 is a greenhouse gas. C N2 is acidic. D N2 is toxic.

Question

Some gases are present in clean, dry air, while other gases are only present in polluted air. Which row is correct? a gas present a gas only present in clean, dry air in polluted air A argon carbon dioxide B argon nitrogen dioxide C sulfur dioxide carbon dioxide D sulfur dioxide nitrogen dioxide

Question

Petroleum is separated by fractional distillation. Which statement about the fractions produced is correct? A Bottled gas for heating and cooking is obtained from the naphtha fraction. B Diesel oil is used as a fuel for jet aircraft. C Substances used to make polishes are obtained from the lubricating fraction. D The kerosene fraction contains many useful waxes.

Question

Which structure represents a compound in the alcohol homologous series? A B C D H H H H H H H H H O H C C H H C C C H C C C H H C C C H H H O H H H H H H O H H

Question

Ethane reacts with chlorine. Which row identifies the type of reaction and the formulae of the products formed? reaction products A addition CH3CH2Cl + H2 B addition CH3CH2Cl + HCl C substitution CH3CH2Cl + HCl D substitution CH3CH2Cl + H2

Question

Which equation represents the formation of poly(propene) from propene? A B CH3 H CH3 H H H H H n C C C C n C C C C H H H H n H H H H n C D CH3 H CH3 H CH3 H H H H n C C C C n C C C C C H H H H n H H H H H n

Question

Ethene reacts with hydrogen in an addition reaction to form ethane. Which catalyst is used for this reaction? A iron B nickel C vanadium(V) oxide D yeast

Question

What is produced by the bacterial oxidation of ethanol? A ethene B sodium ethanoate C ethyl ethanoate D vinegar

Question

Which statement about addition polymers or condensation polymers is correct? A Addition polymers only contain carbon and hydrogen atoms. B One of the monomers used to make a polyester is a diamine. C Addition polymers contain carbon–carbon double bonds in the main chain. D Water is an additional product in the formation of a protein from amino acids.

Question

The results of flame tests on three metal salts, X, Y and Z, are shown. metal salt flame test colour X yellow Y lilac Z blue-green Which row identifies the cations present in X, Y and Z? X Y Z A potassium sodium calcium B potassium sodium copper C sodium potassium calcium D sodium potassium copper

Question

Ethanol can be made by fermentation of sugar, using yeast. This produces a mixture of ethanol and water. How is ethanol separated from this mixture? A distilling the mixture using a fractionating column B filtering the mixture C heating to evaporate most of the water, and allowing the ethanol to crystallise D heating to evaporate the water 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 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.).