Chemistry 0620/42 February/March 2020: question paper and mark scheme

Question

Petroleum is a useful natural resource. The diagram shows how petroleum can be separated into useful substances. refinery gas gasoline fraction A kerosene fraction diesel oil fuel oil fraction lubricating oil fraction petroleum B (a) What is the name of the separation process shown in the diagram? . …… [2] (b) Name the fraction leaving at: A …… B …… [2] (c) Refinery gas is a mixture of hydrocarbons. One refinery gas is butane, C4H10. (i) Suggest the names of two other refinery gases. …… and . …… [2] (ii) Write the chemical equation for the complete combustion of butane. . …… [2] (iii) Name the toxic gas produced by the incomplete combustion of butane. . …… [1] (d) Gasoline and kerosene are both fuels. They have different properties. (i) Describe the differences in the properties given. viscosity of the fuel …… . …… flammability of the fuel . …… . …… [2] (ii) What difference in the molecules of gasoline and kerosene causes these differences in properties? . …… [1] (e) Hydrogen fuel cells can be used to power vehicles. Write the word equation for the overall reaction that takes place in a hydrogen fuel cell. . …… [1] [Total: 13]

Question

Aluminium is extracted from its ore. The ore is converted into pure aluminium oxide, which then undergoes electrolysis as shown. + power – supply wires anodes + + cathode electrolyte molten aluminium (a) (i) Name an ore of aluminium. . …… [1] (ii) What is meant by the term electrolysis? . …… . …… [2] (b) Aluminium oxide has a melting point of about 2000 °C, but the electrolysis process operates at about 900 °C. (i) Name the compound added to aluminium oxide to reduce the operating temperature. . …… [1] (ii) Suggest one benefit to the environment of reducing the operating temperature. . …… . …… [1] (iii) Write the ionic half-equation for the reaction taking place at: the negative electrode (cathode) …… the positive electrode (anode) …… [4] (iv) Explain why the anodes need frequent replacement. . …… . …… [2] (c) Aluminium oxide reacts with acids and with alkalis. (i) What term is used to describe an oxide that reacts with acids and with alkalis? . …… [1] (ii) Aluminium oxide reacts with dilute sulfuric acid to form a salt. State the name and write the formula of the salt formed. name . …… formula . …… [2] (iii) Aluminium oxide reacts with dilute sodium hydroxide to form a salt and one other product. Name the other product. . …… [1] (iv) Aluminium hydroxide, Al (OH)3, decomposes when heated to form aluminium oxide and water. Write the chemical equation for this reaction. . …… [2] (v) Suggest the names of two other aluminium compounds that decompose when heated to form aluminium oxide. . …… . …… [2] [Total: 19]

Question

The Periodic Table is a method of classifying elements. (a) Identify the element which is in Group VI and Period 4. . …… [1] (b) Calcium is in Group II and chlorine is in Group VII of the Periodic Table. Explain, in terms of number of outer shell electrons and electron transfer, how calcium atoms and chlorine atoms form ions. Give the formulae of the ions formed. . …… . …… . …… . …… . …… . …… . …… [5] (c) Group V chlorides are covalent molecules. The boiling points of some Group V chlorides are shown. chloride boiling point / °C NCl 3 71 PCl 3 AsCl 3 130 SbCl 3 283 (i) Suggest the approximate boiling point of PCl 3. . …… [1] (ii) Explain the trend in boiling points in terms of attractive forces between particles. . …… . …… [2] (iii) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of PCl 3. Show outer electrons only. Cl Cl P Cl [3] (d) PCl 3 reacts with chlorine, Cl 2, to form PCl 5. This reaction is exothermic and reaches an equilibrium. PCl 3(g) + Cl 2(g) PCl 5(g) (i) Describe two features of an equilibrium. . …… . …… . …… [2] (ii) State the effect, if any, on the position of this equilibrium when the following changes are made. Explain your answers. temperature is increased …… . …… pressure is increased …… . …… [4] (iii) Explain, in terms of particles, what happens to the rate of the forward reaction when the reaction mixture is heated. . …… . …… . …… . …… . …… [3] (e) PCl 5 reacts with lithium fluoride, LiF, to form LiPF6. PCl 5 + 6LiF → LiPF6 + 5LiCl Calculate the mass of LiF needed to form 3.04 g of LiPF6 using the following steps. ●● Calculate the number of moles of LiPF6 formed. [Mr: LiPF6, 152] number of moles = …… ●● Deduce the number of moles of LiF needed. number of moles = …… ●● Calculate the mass of LiF needed. mass = …… g [3] (f) Lithium fluoride has ionic bonding. (i) What is an ionic bond? . …… . …… [2] (ii) Give two physical properties of ionic compounds. . …… . …… [2] [Total: 28]

Question

Iron is a typical transition element. Iron: ●● acts as a catalyst ●● forms coloured compounds ●● has more than one oxidation state. (a) Name one major industrial process that uses iron as a catalyst and name the product made in this process. process …… product made . …… [2] (b) When aqueous sodium hydroxide is added to aqueous iron(II) sulfate, a precipitate forms. (i) What colour is this precipitate? . …… [1] (ii) Write the ionic equation for this reaction. Include state symbols. . …… [3] (c) Iron(II) sulfate can be converted to iron(III) sulfate by potassium manganate(VII) at room temperature. (i) What is the role of potassium manganate(VII) in this reaction? . …… [1] (ii) What condition must be used for this reaction to occur? . …… [1] (iii) In terms of electron transfer, what happens to the iron(II) ions in this reaction? . …… [1] (iv) State the colour change seen during this reaction. from purple to …… [1] (d) Deduce the charge on the iron ion in each of these compounds. FeF3 …… Fe(NO3)3 …… [2] [Total: 12]

Question

There are two types of polymers. (a) Addition polymers are made from many identical small units. (i) What is the term used to describe these small units? . …… [1] (ii) A section of an addition polymer is shown. H CH3 H CH3 H CH3 C C C C C C H CH3 H CH3 H CH3 Draw the structure of the small unit used to make this addition polymer. Show all of the atoms and all of the bonds. [2] (b) Polyamides are condensation polymers. What does the term condensation mean when used to describe this type of polymer? . …… [1] (c) A polyamide can be made from two different molecules. A simplified structure of octanedioic acid is shown. O O H O C C O H A simplified structure of 1,6-diaminohexane is shown. H H N N H H (i) Complete the diagram to show a section of polyamide manufactured from octanedioic acid and 1,6-diaminohexane. Include all of the atoms and all of the bonds in the linkages. [3] (ii) State the name of a synthetic polyamide. . …… [1] [Total: 8] 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 12 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 89–103 104 105 106 107 108 109 110 111 112 114 116 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium flerovium livermorium – – – – – – – – – – – – – 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.).