Chemistry 0620/41 October/November 2020: question paper and mark scheme

Question

(a) This question is about elements. aluminium carbon iron hydrogen oxygen silicon sodium sulfur Answer the following questions about these elements. Each element may be used once, more than once or not at all. (i) Name the element that can be used as a fuel. . …… [1] (ii) Name the element that forms an oxide with a similar structure to diamond. . …… [1] (iii) Name the element that forms an amphoteric oxide. . …… [1] (iv) Name the element that has oxidation states of +2 and +3. . …… [1] (v) Name the element extracted from bauxite. . …… [1] (vi) Name the element that has atoms with the electronic structure 2,6. . …… [1] (b) Iron rusts when it is in contact with oxygen and water. (i) Explain how sacrificial protection prevents rusting. . …… . …… . …… . …… [2] (ii) State one other method of rust prevention. . …… [1] [Total: 9]

Question

Zinc is extracted from an ore containing zinc sulfide. (a) State the name of this zinc ore. . …… [1] (b) This ore is converted to zinc oxide, ZnO. Zinc oxide is then reacted with carbon. (i) Write a chemical equation for the reaction of zinc oxide with carbon. . …… [1] (ii) State what type of chemical change happens to the zinc in zinc oxide in this reaction. Explain your answer. chemical change . …… explanation …… . …… . …… [2] (iii) Explain why aluminium is not extracted from aluminium oxide by heating with carbon. . …… . …… [1] (iv) Suggest an alternative method for the extraction of zinc from zinc oxide. . …… [1] (c) Brass is an alloy of zinc. Explain, in terms of particles, why brass is harder than pure zinc. . …… . …… . …… . …… . …… [3] [Total: 9]

Question

(a) Aqueous ammonium sulfate, (NH4)2SO4, is warmed with aqueous sodium hydroxide. The pungent-smelling gas ammonia, NH3, is produced. Balance the equation for this reaction. (NH4)2SO4 + ……NaOH → ……NH3 + ……H2O + Na2SO4[1] (b) A 2.8 g sample of impure ammonium sulfate is found to contain 0.7 g of impurities. Calculate the percentage of ammonium sulfate in this sample. percentage of ammonium sulfate = …… % [1] (c) Describe a test for ammonia gas. test . …… result . …… [2] (d) Ammonia gas is prepared at the front of a laboratory. The pungent smell of ammonia spreads throughout the laboratory slowly. (i) Name the process that occurs when ammonia gas spreads throughout the laboratory. . …… [1] (ii) Explain, using ideas about particles, why ammonia gas spreads throughout the laboratory. . …… . …… . …… . …… [2] (iii) Explain why carbon dioxide gas, CO2, will spread throughout the laboratory at a slower rate than ammonia gas, NH3. . …… . …… [1] (e) Ammonia is produced in the Haber process. The equation for the reaction is shown. N2(g) + 3H2(g) → 2NH3(g) (i) In the Haber process, a temperature of 450 °C and a pressure of 200 atmospheres are used in the presence of finely‑divided iron. A larger equilibrium yield of ammonia would be produced if a lower temperature and a higher pressure are used. Explain why a lower temperature and a higher pressure are not used. lower temperature . …… . …… higher pressure . …… . …… [2] (ii) State the role of iron in the Haber process. . …… [1] (f) Ammonia is a weak base. (i) Explain the meaning of the term base. . …… . …… [1] (ii) Suggest the pH of aqueous ammonia. . …… [1] [Total: 13]

Question

Air is a mixture of gases. (a) State the percentage of clean dry air which is oxygen. Give your answer to the nearest whole number. …… % [1] (b) Oxygen and nitrogen are useful gases that can be obtained from air. (i) Name the process used to separate oxygen and nitrogen from liquid air. . …… [2] (ii) State the property of oxygen and nitrogen that allows these gases to be separated using this process. . …… [1] (c) Carbon dioxide, CO2, is a covalent molecule. Complete the diagram to show the electron arrangement in one molecule of CO2. Show only the outer electrons. O C O [2] (d) The graph shows the concentration of carbon dioxide in the atmosphere over a 60‑year period, measured in parts per million (ppm). 420 400 380 concentration of carbon dioxide / ppm 360 340 320 1960 1970 1980 1990 2000 2010 2020 year The data shown in the graph is of global concern. Explain why. . …… . …… . …… . …… . …… . …… [3] (e) Name the process in the carbon cycle by which plants remove carbon dioxide from the atmosphere. . …… [1] [Total: 10]

Question

(a) Dilute sulfuric acid is electrolysed using the apparatus shown in the diagram. power supply + – inert electrodes dilute sulfuric acid (i) State what is meant by the term electrolysis. . …… . …… . …… [2] (ii) Explain why inert electrodes are used. . …… . …… [1] (iii) Name the products formed at each electrode. negative electrode …… positive electrode . …… [2] (iv) Write an ionic half‑equation for the reaction at the negative electrode. . …… [2] (b) Sulfuric acid is manufactured using the Contact process. This manufacture involves four stages. (i) Stage 1 involves the combustion of sulfur to form sulfur dioxide. Write the chemical equation for stage 1. . …… [1] (ii) The equation for stage 2 is shown. 2SO2(g) + O2(g) 2SO3(g) The reaction can reach equilibrium. Explain what is meant by the term equilibrium. . …… . …… . …… . …… [2] (iii) The energy level diagram for the forward reaction in stage 2 is shown. 2SO2(g) + O2(g) energy 2SO3(g) progress of reaction Explain what the diagram shows about the energy changes in the forward reaction. . …… . …… . …… . …… [2] (c) In stage 3 sulfur trioxide, SO3, is converted to oleum, H2S2O7. In stage 4 oleum reacts to form sulfuric acid, H2SO4. State what oleum reacts with in stage 4. . …… [1] (d) A sample of sulfuric acid, H2SO4, has a concentration of 0.75 mol / dm3. Calculate the concentration of sulfuric acid in g / dm3. …… g / dm3 [2] [Total: 15]

Question

(a) Ethane, propane and butane are members of the same homologous series. (i) Name this homologous series. . …… [1] (ii) State two ways members of the same homologous series are similar. 1 . …… 2 . …… [2] (b) One mole of ethane, C2H6, contains 6.02 × 1023 molecules. Calculate how many molecules are in 15 g of ethane. number of ethane molecules = …… [1] (c) Propane reacts with chlorine. (i) Write the formula of the product which does not contain carbon. . …… [1] (ii) Draw the structure of an organic product formed. Show all of the atoms and all of the bonds. [1] (iii) State the name of this type of reaction. . …… [1] (d) (i) Aqueous bromine was added to a sample of ethene. Give the colour change seen. from …… to …… [2] (ii) Explain, in terms of bonding, why there is no colour change when aqueous bromine is added to ethane. . …… . …… [1] (e) There are two structural isomers with the formula C4H10. (i) Draw the structures of both of these isomers, showing all of the atoms and all of the bonds. [2] (ii) Butane is formed when longer chain hydrocarbons are cracked. Complete the chemical equation to show the other product when butane is formed by cracking. C6H14 → C4H10 + …… [1] (f) A compound contains 85.7% carbon and 14.3% hydrogen by mass. (i) Calculate the empirical formula of this compound. Show your working. …… [2] (ii) The molecular mass of the compound is 112. Calculate the molecular formula of this compound. …… [1] [Total: 16]

Question

(a) Ethanol can be manufactured by two different methods. Method 1: fermentation of a sugar, C6H12O6 C6H12O6 → 2C2H5OH + 2CO2 Method 2: reaction of ethene with steam C2H4 + H2O → C2H5OH (i) Give one advantage of using fermentation compared with Method 2. . …… . …… [1] (ii) Give one disadvantage of using fermentation compared with Method 2. . …… . …… [1] (b) Ethanol reacts with acidified potassium manganate(VII) to form water and a product that turns litmus red. (i) State the name of the product that turns the litmus red. . …… [1] (ii) State the type of reaction that ethanol undergoes when it reacts with acidified potassium manganate(VII). . …… [1] (c) Ethanol reacts with methanoic acid to form an ester. (i) Name the ester formed in this reaction. . …… [1] (ii) Draw the structure of the ester formed. Show all of the atoms and all of the bonds. [1] (d) The table shows the melting points of ethanol and sodium chloride. substance melting point / °C ethanol –114 sodium chloride 801 The difference in melting points is due to differences in attractive forces between particles in these substances. Name the type of attractive force in each substance, which is responsible for the difference in melting points. ethanol . …… sodium chloride …… [2] [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 20 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.).