Chemistry 0620/42 October/November 2023: question paper and mark scheme

Question

Table 1.1 gives the electronic configurations of some atoms and ions, A to G. Table 1.1 electronic configuration A 2,5 B 2,8 C 2,8,2 D 2,8,4 E 2,8,5 F 2,8,6 G 2,8,18,7 Answer the following questions about A to G. Each letter may be used once, more than once or not at all. State which of the atoms or ions, A to G, could be: (a) a noble gas atom . …… [1] (b) an atom of an element in Group VI . …… [1] (c) an atom with an atomic number of 14 . …… [1] (d) atoms from the same group …… and . …… [1] (e) a halogen atom . …… [1] (f) an atom of an element which is a good conductor of electricity . …… [1] (g) a stable ion of a Group V element . …… [1] (h) an atom that forms an ion with a 2– charge. . …… [1] [Total: 8]

Question

Cobalt and copper are transition elements. (a) Copper has two naturally occurring isotopes, 63Cu and 65Cu. Cobalt has only one naturally occurring isotope, 59Co. (i) Complete Table 2.1 to show the number of protons, neutrons and electrons in the 59Co atom and the 65Cu2+ ion. Table 2.1 59 Co 65 Cu2+ protons neutrons electrons [3] (ii) Table 2.2 shows the relative abundance of the two naturally occurring isotopes of copper. Table 2.2 isotope 63 Cu 65 Cu relative abundance 70% 30% Calculate the relative atomic mass of copper to one decimal place. relative atomic mass = …… [2] (b) One physical property of transition elements such as copper and cobalt is that they are hard. Other metals such as lithium are softer. State two other physical properties of copper and cobalt which are significantly different from lithium. 1 . …… 2 . …… [2] (c) Both copper and cobalt can form coloured compounds. Some of these compounds contain water of crystallisation. (i) Define the term water of crystallisation. . …… . …… [2] (ii) State the colour and formula of hydrated cobalt(II) chloride crystals. colour . …… formula . …… [2] (iii) State the colour change seen when a few drops of water are added to anhydrous copper(II) sulfate. (iv) State how this colour change can be reversed. . …… [1] [Total: 14]

Question

Iron is manufactured in a blast furnace. (a) Three of the starting materials added to the blast furnace are coke, iron ore and limestone. Name the other starting material added to the blast furnace. . …… [1] (b) The source of iron in the blast furnace is Fe2O3. Fe2O3 is found in iron ore. (i) Name the main ore of iron which contains Fe2O3. . …… [1] (ii) The iron in Fe2O3 is reduced by reaction with carbon monoxide. The unbalanced symbol equation is shown. Complete the equation. Fe2O3 + ……CO → ……CO2 + ……Fe [1] (iii) State the change in oxidation number of iron in the reaction in (ii). (iv) Explain how the change of oxidation number shows that iron has been reduced. . …… [1] (c) The major impurity in iron ore is silicon(IV) oxide. Limestone is added to the blast furnace to remove this impurity. Write two symbol equations to show how silicon(IV) oxide is removed. For each equation, state the type of chemical reaction that takes place. equation 1 . …… type of chemical reaction . …… equation 2 . …… type of chemical reaction . …… [4] (d) Iron is converted to steel by mixing it with carbon and other elements. (i) State the term given to a substance which is a mixture of a metal and other elements. . …… [1] (ii) Name one element, other than carbon, mixed with iron in the making of stainless steel. . …… [1] (e) Preventing the rusting of steel is important. State the chemical name of rust. . …… [1] (f) Steel can be coated with zinc to prevent rusting. This provides both a barrier method and sacrificial protection. (i) State the term used for coating steel with zinc. . …… [1] (ii) Describe another barrier method for preventing rusting. . …… [1] (iii) Explain how zinc provides sacrificial protection. . …… . …… [2] [Total: 17]

Question

This question is about lead(II) chloride, PbCl 2. (a) A student prepares a sample of insoluble lead(II) chloride, PbCl 2, by mixing aqueous solutions of two salts in a beaker. (i) Identify two soluble salts suitable for making lead(II) chloride when mixed together. . …… . …… [2] (ii) Write the ionic equation for the formation of lead(II) chloride by mixing aqueous solutions. Include state symbols. . …… [3] (iii) List the steps the student should take in preparing a pure sample of lead(II) chloride from the mixture in the beaker. . …… . …… . …… [3] (b) The student carries out an electrolysis experiment on molten lead(II) chloride using the apparatus shown in Fig. 4.1. Chlorine gas forms at the anode and escapes from the apparatus. power supply molten lead(II) chloride Fig. 4.1 (i) Explain why lead(II) chloride needs to be molten before it will conduct electricity. . …… . …… [1] (ii) Write the ionic half-equation for the reaction occurring at the anode. . …… [2] (iii) State the test for chlorine gas. test . …… observations …… [2] (iv) Describe what is observed at the cathode. . …… [1] [Total: 14]

Question

Chemical reactions can involve transfer of thermal energy. (a) State the term used for the transfer of thermal energy during a reaction. . …… [1] (b) Tetrachloromethane gas, CCl 4(g), reacts with steam as shown. CCl 4(g) + 2H2O(g) CO2(g) + 4HCl (g) The reaction is reversible. The forward reaction is exothermic. (i) State what happens, if anything, to the rate of the forward reaction if the concentration of CCl 4 is increased. Explain your answer in terms of collision theory. . …… . …… . …… . …… [3] (ii) State what happens to the position of equilibrium, if anything, when the pressure is increased. Explain your answer. . …… . …… [2] (iii) Fig. 5.1 shows an incomplete reaction pathway diagram for the forward reaction. CCl 4(g) + 2H2O(g) CO2(g) + 4HCl (g) energy progress of reaction Fig. 5.1 On Fig. 5.1: ● insert the formulae of the reactants and products ● draw an arrow, labelled Ea, to show the activation energy ● draw an arrow, labelled ∆H, to show the transfer of energy in the reaction. [3] (iv) Define the term activation energy. . …… . …… [2] (v) State one way in which the activation energy of a reaction can be changed. . …… [1] (c) The equation for the reaction between tetrachloromethane gas and steam can be represented as shown in Fig. 5.2. Cl H Cl H O H H Cl Cl C Cl + O C O + H = –130 kJ / mol H O H H Cl H Cl Cl Fig. 5.2 Table 5.1 shows some bond energies. Table 5.1 bond C–Cl H–O C=O bond energy in kJ / mol 340 460 805 Use the bond energies in Table 5.1 and the ∆H value for the reaction to calculate the H–Cl bond energy using the following steps. ● Calculate the energy needed to break the bonds in the reactants. …… kJ ● Calculate the energy released when the bonds in carbon dioxide form. …… kJ ● Calculate the H–Cl bond energy. …… kJ / mol [4] [Total: 16]

Question

A homologous series is a family of organic compounds whose members have similar chemical properties. (a) Give two characteristics that are the same for all members of a homologous series. 1 . …… 2 . …… [2] (b) In terms of structure, state how one member of a homologous series differs from the next member of that homologous series. . …… [1] (c) A, B and C are organic compounds. A has the molecular formula C12H24. B has the name tetradecane. C has three carbon atoms and is in the homologous series with the general formula CnH2n+1COOH. (i) Name the homologous series each organic compound belongs to. A …… B …… C …… [3] (ii) Name C and draw its displayed formula. name . …… displayed formula [2] (d) Amino acids are a homologous series where each member has the general structure shown in Fig. 6.1. The R side chain contains carbon and hydrogen atoms only. H R O N C C H H O H Fig. 6.1 (i) An amino acid has a relative molecular mass of 103. Deduce the formula of the R side chain in this amino acid. Show your working. . …… [2] (ii) State the name given to the natural polyamides formed from amino acid monomers. . …… [1] [Total: 11] 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.).