Chemistry 0620/43 October/November 2019: question paper and mark scheme

Question

(a) Atoms are made of smaller particles called electrons, neutrons and protons. Complete the table. particle relative charge relative mass 1 electron 1840 neutron proton +1 [2] (b) The table gives information about atoms and ions A, B and C. Complete the table. number of number of number of symbol electrons neutrons protons A 14 13 13Al 27 B 12 12Mg 25 2+ C 10 10 9 [6] [Total: 8]

Question

The table shows the melting points, boiling points and electrical conductivities of six substances D, E, F, G, H and I. melting point boiling point electrical conductivity electrical conductivity substance / °C / °C when solid when liquid D 1610 2230 non-conductor non-conductor E 801 1413 non-conductor good conductor F –119 43 non-conductor non-conductor G 1535 2750 good conductor good conductor H 114 184 non-conductor non-conductor I –210 –196 non-conductor non-conductor Choose substances from the table which match the following descriptions. Each substance may be used once, more than once or not at all. (a) Which substance is a liquid at 25 °C? . …… [1] (c) Which three substances contain simple molecules? . …… [3] (d) Which substance could be a metal? Give a reason for your answer. substance …… reason . …… . …… [2] (e) Which substance has a macromolecular structure? Give two reasons for your answer. substance …… reason 1 . …… reason 2 . …… [3] (f) Which substance is an ionic solid? Give one reason for your answer. substance …… reason . …… . …… [2] [Total: 12]

Question

(a) Name the ore of aluminium which mainly consists of aluminium oxide. . …… [1] (b) Aluminium is produced by the electrolysis of aluminium oxide dissolved in molten cryolite. waste gases positive electrode molten mixture of negative electrode aluminium oxide and cryolite aluminium (i) Give two reasons why the electrolysis is done using a molten mixture of aluminium oxide and cryolite instead of molten aluminium oxide only. 1 . …… 2 . …… [2] (ii) Write ionic half-equations for the reactions occurring at the electrodes. positive electrode . …… negative electrode …… [2] (iii) The anodes are made of carbon and have to be replaced regularly. Explain why the carbon anodes have to be replaced regularly. . …… . …… [2] (c) The positions of some common metals in the reactivity series are shown. most reactive magnesium aluminium least reactive copper (i) When magnesium is placed in aqueous copper(II) sulfate a displacement reaction occurs immediately. Write an ionic equation for the reaction. Include state symbols. . …… [2] (ii) State two observations you would make when magnesium is placed in aqueous copper(II) sulfate. 1 . …… 2 . …… [2] (iii) When aluminium foil is added to aqueous copper(II) sulfate no immediate reaction takes place. Explain why. . …… [1] (d) Aluminium powder reacts with iron(III) oxide to produce aluminium oxide and iron. Write a chemical equation for this reaction. . …… [2] [Total: 14]

Question

This question is about phosphorus and compounds of phosphorus. (a) A phosphorus molecule contains four phosphorus atoms only. What is the formula of a phosphorus molecule? . …… [1] (b) Phosphorus reacts with chlorine gas to produce phosphorus(III) chloride, PCl 3. (i) Write a chemical equation for the reaction between phosphorus and chlorine to produce phosphorus(III) chloride, PCl 3. . …… [2] (ii) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of phosphorus(III) chloride, PCl 3. Show outer shell electrons only. Cl Cl P Cl [2] (c) Gaseous phosphorus(III) chloride, PCl 3, reacts with gaseous chlorine to form gaseous phosphorus(V) chloride, PCl 5. PCl 3(g) + Cl 2(g) PCl 5(g) The chemical equation for this reaction can be represented as shown. Cl Cl Cl Cl P Cl + Cl Cl P Cl Cl Cl (i) Use the bond energies in the table to calculate the energy change, in kJ / mol, of the reaction. bond bond energy in kJ / mol P– Cl 326 Cl – Cl 243 ●● Energy needed to break bonds. …… kJ ●● Energy released when bonds are formed. …… kJ ●● Energy change of reaction. energy change = …… kJ / mol [3] (ii) Deduce whether the energy change for this reaction is exothermic or endothermic. Explain your answer. . …… . …… [1] (d) Under certain conditions the reaction reaches equilibrium. PCl 3(g) + Cl 2(g) PCl 5(g) State and explain the effect, if any, on the position of equilibrium if the pressure is increased. All other conditions are unchanged. . …… . …… . …… [2] (e) Phosphine, PH3, is produced by the reaction between water and calcium phosphide, Ca3P2. Balance the chemical equation for this reaction. Ca3P2 + ……H2O ……Ca(OH)2 + ……PH3[2] (f) The phosphonium ion, PH4+, is similar to the ammonium ion. (g) Calcium phosphate contains the phosphate ion, PO43–. What is the formula of calcium phosphate? . …… [1] (h) Phosphorus forms another compound with hydrogen with the following composition by mass: P, 93.94%; H, 6.06%. (i) Calculate the empirical formula of the compound. empirical formula = …… [2] (ii) The compound has a relative molecular mass of 66. Deduce the molecular formula of the compound. molecular formula = …… [1] [Total: 19]

Question

Nitrates such as ammonium nitrate are used as fertilisers. The final stage in the production of ammonium nitrate is shown in the equation. Ca(NO3)2 + 2NH3 + CO2 + H2O 2NH4NO3 + CaCO3 Calculate the maximum mass of ammonium nitrate that can be produced from 820 g of calcium nitrate, Ca(NO3)2, using the following steps. The relative formula mass, Mr, of calcium nitrate, Ca(NO3)2, = 164. ●● Calculate the number of moles of Ca(NO3)2 in 820 g. …… mol ●● Deduce the number of moles of NH4NO3 produced. …… mol ●● Calculate the Mr of NH4NO3. Mr of NH4NO3 = …… ●● Calculate the maximum mass of ammonium nitrate produced. …… g [4]

Question

This question is about sulfuric acid and substances that can be made from sulfuric acid. (a) Sulfuric acid is a strong acid. What is meant by the term strong acid ? strong . …… acid …… [2] (b) Dilute sulfuric acid and aqueous sodium hydroxide are used to make aqueous sodium sulfate, Na2SO4(aq), or aqueous sodium hydrogen sulfate, NaHSO4(aq). The method includes use of the following apparatus. dilute sulfuric acid conical flask 25.0 cm3 of aqueous sodium hydroxide 25.0 cm3 of aqueous sodium hydroxide of concentration 0.100 mol / dm3 was neutralised by 25.0 cm3 of dilute sulfuric acid of concentration 0.0500 mol / dm3. The equation for the reaction is shown. This is reaction 1. 2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l) reaction 1 The same technique and the same solutions can be used to make aqueous sodium hydrogen sulfate. The equation for the reaction is shown. This is reaction 2. NaOH(aq) + H2SO4(aq) NaHSO4(aq) + H2O(l) reaction 2 Complete the table to calculate the volume of dilute sulfuric acid that reacts with 25.0 cm3 of aqueous sodium hydroxide in reaction 2. volume of 0.0500 mol / dm3 volume of 0.100 mol / dm3 dilute sulfuric acid in cm3 aqueous sodium hydroxide in cm3 reaction 1 25.0 25.0 reaction 2 25.0 [1] (c) Aqueous sodium hydrogen sulfate, NaHSO4(aq), contains the ions Na+(aq), H+(aq) and SO42–(aq). Describe what you would see if the following experiments were done. (i) A flame test was done on aqueous sodium hydrogen sulfate. . …… [1] (ii) Solid copper(II) oxide was added to aqueous sodium hydrogen sulfate and the mixture was warmed. . …… . …… [2] (d) A test can be done to show the presence of SO42–(aq) by adding acidified aqueous barium chloride or acidified aqueous barium nitrate. (i) State the observation that would show that SO42– is present. . …… [1] (ii) Write an ionic equation for the reaction that occurs if SO42– is present. Include state symbols. . …… [2] [Total: 9]

Question

Addition polymerisation and condensation polymerisation are two types of polymerisation. (a) Which functional group is present in all the monomers which are used to make addition polymers? . …… [1] (b) Part of an addition polymer is shown. CH3 CH3 CH3 CH3 CH3 CH3 C C C C C C H H H H H H (i) How many monomer units are needed to make the part of the addition polymer shown? . …… [1] (ii) Draw the structure of the monomer that is used to make this addition polymer. Show all of the atoms and all of the bonds. Name the monomer. name . …… [2] (iii) State the empirical formula of: the monomer …… the polymer. …… [2] (c) Complex carbohydrates are natural condensation polymers. They can be broken down into colourless monomers which can then be separated and identified. X is a complex carbohydrate. Starting with a sample of X, describe how to produce, separate, detect and identify the monomers which make it up. Your answer should include: ●● the name of the process used to break down X into its monomers ●● two types of substance that can be used to break down X ●● the name of the process used to separate the monomers ●● the method used to detect the monomers after they have been separated ●● the method used to identify the monomers after they have been separated and detected. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [6] (d) Synthetic polyamides are condensation polymers. (i) Name a synthetic polyamide. . …… [1] (ii) Synthetic polyamides can be made by reacting carboxylic acids with amines. Name the other substance that is produced in this reaction. . …… [1] [Total: 14] 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 89–103 104 105 106 107 108 109 110 111 112 114 116 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.).