0620 Chemistry November 2025 Question Paper 43

1 Atoms and ions are made from particles called electrons, neutrons and protons.

(a) Complete Table 1.1. Table 1.1 particle relative charge relative mass electron –1 1 1840 neutron proton [2]

(b) Table 1.2 shows information about some atoms or ions.

Complete Table 1.2. Table 1.2 atom or ion number of electrons number of neutrons number of protons 4 2 0 0Ca2+ 20 20 19 9F 9 9 10 9 8 [5]

(c) (i) The relative atomic mass, Ar, of an element is the average mass of its isotopes compared to one atom of isotope X.

Identify isotope X [1]

(ii) A sample of magnesium consists of two isotopes with mass numbers 24 and 26. [Ar: Mg, 24.3]

Calculate the percentage abundance of the isotope of magnesium with mass number 24.

percentage abundance = [1] [Total: 9] , ,

2 Table 2.1 shows the melting points, boiling points and electrical conductivities of seven substances, A, B, C, D, E, F and G. Table 2.1 substance melting point / °C boiling point / °C electrical conductivity when solid electrical conductivity when molten A 1600 2230 poor poor B –219 –183 poor poor C 770 1420 poor good D –39 357 good good E –7 58 poor poor F 44 280 poor poor G 1085 2562 good good

(a) Identify which substance, A, B, C, D, E, F or G, is:

(i) a gas at 25 °C [1]

(ii) a solid consisting of simple molecules at 25 °C [1]

(iii) a metal which is liquid at 25 °C [1]

(b) (i) Identify which substance, A, B, C, D, E, F or G, has a giant covalent structure.

Use the information in Table 2.1 to give two reasons for your choice. substance reason 1 reason 2 [3]

(ii) Identify which substance, A, B, C, D, E, F or G, is an ionic compound.

Use the information in Table 2.1 to give one reason for your choice. substance reason [2]

[Total: 8] , ,

3 This question is about aluminium and other metallic elements.

(a) Aluminium is extracted from purified bauxite by electrolysis. Fig. 3.1 shows a diagram of the electrolytic cell used. waste gases negative electrode aluminium electrolyte positive electrodes Fig. 3.1

(i) State the name of the aluminium compound present in bauxite [1]

(ii) Name the substance that purified bauxite is dissolved in before electrolysis is carried out [1]

(iii) Name the substance that is used for the positive electrodes [1]

(iv) Write the ionic half-equation for the production of aluminium at the negative electrode [2]

(b) Aluminium is above zinc in the reactivity series.

(i) When a piece of aluminium foil is added to aqueous zinc sulfate, a reaction is not immediately observed even though aluminium is above zinc in the reactivity series.

Explain why a reaction is not immediately observed [1]

(ii) After a few minutes, a displacement reaction occurs between aluminium and aqueous zinc ions.

Complete the ionic equation for this reaction Al + Zn2+ Al 3+ + Zn [1] , ,

(iii) State the oxidation number of zinc in: Zn2+ Zn [2]

(iv) Define the term reduction in terms of oxidation number [1]

(c) Aluminium reacts with iron(III) oxide. The equation is shown. 2Al + Fe2O3 Al 2O3 + 2Fe ΔH = – 850 kJ / mol

(i) State the meaning of the symbol ΔH [1]

(ii) State what can be deduced about the reaction from the negative sign in ΔH = – 850 kJ / mol [1]

(d) Gallium has many similarities to aluminium. Gallium(III) oxide is an amphoteric oxide.

State what is meant by the term amphoteric [1]

(e) The reaction of gallium(III) oxide, Ga2O3, with aqueous sodium hydroxide forms a salt which contains the negative ion GaO2 –. The only other product is water.

Write a symbol equation for this reaction [2]

(f) Deduce the formula of: • gallium(III) bromide • gallium(III) sulfate [2] [Total: 17] , ,

4 This question is about chlorine and compounds of chlorine.

(a) Gaseous chlorine reacts with gaseous phosphorus(III) chloride to form gaseous phosphorus(V) chloride. The reaction is a reversible reaction.

When the three gases are in a closed container the system reaches equilibrium. Cl 2(g) + PCl 3(g) PCl 5(g)

(i) Describe a reversible reaction at equilibrium in terms of: • the rate of the forward reaction and the rate of the reverse reaction • the concentrations of reactants and products [2]

(ii) Complete Table 4.1 using only the words increases, decreases or no change. Table 4.1 change to condition effect on the rate of the forward reaction effect on the equilibrium concentration of PCl 5 the pressure is decreased a catalyst is added increases

[3]

(iii) When the temperature of the equilibrium mixture is increased, the equilibrium concentration of PCl 5 decreases.

State what conclusion about the forward reaction can be made from this information [1] , ,

(b) Ethene, C2H4, reacts with chlorine, Cl 2, to form 1,2-dichloroethane, CH2Cl CH2Cl .

The equation for this reaction can be represented as shown. H C H H C C Cl Cl Cl Cl + H C H H H H

Table 4.2 shows some bond energies. Table 4.2 bond bond energy in kJ / mol C–C 350 C=C 610 C–H 410 Cl –Cl 240 C–Cl 340

Use the bond energies in Table 4.2 to calculate the enthalpy change, in kJ / mol, of the reaction.

Use the following steps. • Calculate the total energy needed to break the bonds in C2H4 and Cl 2 kJ • Calculate the total energy released when the bonds form in CH2Cl CH2Cl kJ , , • Calculate the enthalpy change of the reaction.

Your answer should include a sign kJ / mol [3]

(c) Chlorine reacts with nitrogen to form nitrogen trichloride, NCl 3.

Complete the dot-and-cross diagram in Fig. 4.1 of a molecule of NCl 3.

Show outer shell electrons only. N Cl Cl Cl Fig. 4.1 [3] , ,

(d) When solid magnesium carbonate, MgCO3, is added to dilute hydrochloric acid, HCl , a chemical reaction occurs. The equation for the reaction is shown. MgCO3(s) + 2HCl (aq) MgCl 2(aq) + CO2(g) + H2O(l)

(i) Give two observations when solid magnesium carbonate is added to dilute hydrochloric acid. 1 2 [2]

(ii) Calculate the volume, in cm3, of CO2(g) that is produced at room temperature and pressure (r.t.p.) when 50.0 cm3 of 0.100 mol / dm3 HCl reacts with excess MgCO3.

The volume of 1 mol of any gas is 24 000 cm3 at r.t.p.

Use the following steps. • Calculate the number of moles of HCl in 50.0 cm3 of 0.100 mol / dm3 HCl mol • Deduce the number of moles of CO2(g) produced mol • Calculate the volume, in cm3, of CO2(g) produced at r.t.p cm3 [3] [Total: 17] , ,

5 This question is about metallic compounds.

(a) Insoluble metal salts, such as lead(II) sulfate, are made by precipitation.

When aqueous lead(II) ions react with aqueous sulfate ions, a precipitate of lead(II) sulfate forms.

A sample of pure lead(II) sulfate can be obtained from the precipitate formed.

(i) Write an ionic equation for this precipitation reaction. Include state symbols [3]

(ii) State the name of an aqueous solution containing lead(II) ions [1]

(iii) State the name of an aqueous solution containing sulfate ions [1]

(iv) The lead(II) sulfate precipitate is separated from the rest of the reaction mixture by filtration. The impure lead(II) sulfate remains on the filter paper.

State the general term given to an insoluble substance that remains on the filter paper during filtration [1]

(v) Describe how the lead(II) sulfate is purified after filtration [2] , ,

(b) Copper is a transition element.

A list of properties of copper is shown. • It has good electrical conductivity. • It has variable oxidation states. • It forms soluble salts. • It forms coloured compounds. • It forms basic oxides. • It acts as a catalyst.

(i) Give two properties from the list that show how copper is similar to metals in Group I of the Periodic Table. 1 2 [2]

(ii) Give two properties from the list that show how copper is different from metals in Group I of the Periodic Table. 1 2 [2] [Total: 12] , ,

6 This question is about organic compounds.

(a) Organic compound Q has the following composition by mass. C, 50.00%; H, 5.56%; O, 44.44%

Calculate the empirical formula of compound Q.

empirical formula = [3]

(b) Organic compound R has the empirical formula CHO and a relative molecular mass of 116.

Determine the molecular formula of compound R.

molecular formula = [1]

(c) Carboxylic acids react with alcohols to form esters.

(i) Name the other product that is formed when a carboxylic acid reacts with an alcohol [1]

(ii) Name the type of catalyst that is used when a carboxylic acid reacts with an alcohol [1]

(iii) Ester S has the structural formula CH3CH2COOCH2CH2CH2CH3.

Name the carboxylic acid and the alcohol which react together to form ester S. carboxylic acid alcohol [2] , ,

(d) Fig. 6.1 shows part of a polymer structure. H CH3 C H CH3 C H CH3 C H CH3 C H CH3 C H CH3 C Fig. 6.1

(i) Name the type of polymerisation that is used to produce this polymer [1]

(ii) Suggest why it is not possible to write the molecular formula of this polymer [1]

(iii) State the number of monomer units that are needed to make the part of the polymer structure shown in Fig. 6.1 [1]

(iv) Draw the displayed formula of the monomer used to make this polymer. [2] , ,

(e) Fig. 6.2 shows part of the general structure of an amino acid. H R C Fig. 6.2

(i) Complete Fig. 6.2 to show all the atoms and all the bonds in the two functional groups of the amino acid. [2]

(ii) Part of a natural polyamide structure is shown in Fig. 6.3. H N H N O C C H O N O C Fig. 6.3

On Fig. 6.3, draw a circle around one amide linkage. [1]

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