Chemistry 0620/43 October/November 2021: question paper and mark scheme

Question

A list of substances is shown. ammonia bauxite carbon dioxide carbon monoxide ethanol hematite oxygen sodium chloride sulfur dioxide Answer the questions using the list of substances. Each substance may be used once, more than once or not at all. State which substance is: (a) an element . …… [1] (b) an ore of aluminium …… [1] (c) a gas that causes acid rain . …… [1] (d) used as a fuel …… [1] (e) an ionic compound …… [1] (f) produced in the Haber process …… [1] (g) a product of respiration . …… [1] (h) a toxic product of the incomplete combustion of hydrocarbons . …… [1] (i) a gas produced in the test for nitrate ions. …… [1] [Total: 9]

Question

This question is about electrolysis. (a) State the meaning of the term electrolyte. . …… . …… [2] (b) The table gives information about the electrolysis of two electrolytes. Carbon (graphite) electrodes are used in each experiment. (i) Complete the table to show the observations and products of electrolysis. positive electrode (anode) negative electrode (cathode) electrolyte observations name of product observations name of product aqueous colourless copper(II) sulfate bubbles concentrated aqueous colourless hydrogen sodium bromide bubbles [5] (ii) Hydrogen is produced at the negative electrode (cathode) during the electrolysis of concentrated aqueous sodium bromide. Write the ionic half-equation for this reaction. . …… [2] (iii) State two reasons why carbon (graphite) is suitable to use as an electrode. 1 . …… 2 . …… [2] (iv) Name the particle responsible for the conduction of electricity in the metal wires used in a circuit. . …… [1] [Total: 12]

Question

Lead is a metallic element in Group IV. One of the ores of lead is galena, which is an impure form of lead(II) sulfide, PbS. Lead also occurs in the ore cerussite, which contains lead(II) carbonate, PbCO3. (a) Calculate the relative formula mass, Mr, of PbCO3. Mr of PbCO3 = …… [1] (b) The Mr of PbS is 239. Calculate the percentage of lead by mass in PbS. percentage of lead by mass in PbS = …… [1] (c) The percentage of lead by mass in PbCO3 is 77.5%. Use this information and your answer to (b) to suggest whether it would be better to extract lead from PbCO3 or PbS. Give a reason for your answer. . …… . …… [1] (d) When lead(II) carbonate is heated it decomposes into lead(II) oxide, PbO, and carbon dioxide. Write a chemical equation for this reaction. . …… [1] (e) Lead(II) carbonate reacts with dilute nitric acid. One of the products is aqueous lead(II) nitrate, Pb(NO3)2. Write a chemical equation for this reaction. . …… [2] (f) Lead(II) oxide and carbon dioxide are oxides of Group IV elements. (i) Complete the diagram to show the electron arrangement in one molecule of CO2. Show only the outer electrons. O C O [2] (ii) The melting points of lead(II) oxide and carbon dioxide are shown. melting point / °C lead(II) oxide 886 carbon dioxide –56 Use your knowledge of structure and bonding to explain why lead(II) oxide has a much higher melting point than carbon dioxide. Your answer should refer to: ● the types of particles involved ● the relative strength of the forces of attraction between the particles. . …… . …… . …… . …… [3] (g) Part of the reactivity series is shown. magnesium most reactive lead copper least reactive Aqueous lead(II) nitrate contains Pb2+ ions. Two experiments are carried out. In Experiment 1, magnesium is added to aqueous lead(II) nitrate. In Experiment 2, copper is added to aqueous lead(II) nitrate. Write an ionic equation for any reaction that occurs in each experiment. If no reaction occurs write ‘no reaction’. Experiment 1 …… Experiment 2 …… [2] (h) When lead(II) nitrate is heated it decomposes to produce the same gaseous products as when copper(II) nitrate is heated. (i) One of the gaseous products is oxygen. Describe a test for oxygen. test . …… observations …… [2] (ii) Name the other gaseous product. . …… [1] [Total: 16]

Question

Carbon is an important element. (a) Carbon exists as the isotopes 126C and 136C. Complete the table. number of protons number of electrons number of neutrons isotope in one atom in one atom in one atom 6C 12 6C 13 [2] (b) Name two forms of the element carbon which have giant covalent structures. …… and . …… [1] (c) The Avogadro constant is the number of particles in 1 mole. The numerical value of the Avogadro constant is 6.02 × 1023. (i) Calculate the number of molecules in 22.0 g of carbon dioxide, CO2. …… molecules [2] (ii) Calculate the number of molecules in 6.00 dm3 of carbon dioxide gas at room temperature and pressure. …… molecules [1] [Total: 6]

Question

(a) Dilute sulfuric acid and aqueous sodium hydroxide can be used to prepare sodium sulfate crystals using a method that involves titration. dilute sulfuric acid conical flask 25.0 cm3 aqueous sodium hydroxide (i) Suggest why universal indicator is not suitable for this titration. . …… [1] (ii) Name an indicator that can be used in this titration. . …… [1] 20.0 cm3 of dilute sulfuric acid neutralises 25.0 cm3 of 1.00 mol / dm3 aqueous sodium hydroxide. At the end of the titration the conical flask contains aqueous sodium sulfate with the dissolved indicator as an impurity. (b) Describe how to prepare a pure sample of sodium sulfate crystals from the original solutions of dilute sulfuric acid and aqueous sodium hydroxide of the same concentrations. You are not required to give details of how to carry out the titration. . …… . …… . …… . …… . …… . …… . …… . …… . …… [5] (c) Sodium hydrogensulfate, NaHSO4, dissolves in water to produce an aqueous solution, X, containing Na+, H+ and SO42– ions. State the observations when the following tests are done. (i) A flame test is carried out on X. . …… [1] (ii) Copper(II) oxide is warmed with an excess of X. . …… . …… [2] (iii) Acidified aqueous barium nitrate is added to X. . …… [1] [Total: 11]

Question

A student investigates the decomposition of hydrogen peroxide in the presence of a catalyst of manganese(IV) oxide. 2H2O2(aq) → 2H2O(l) + O2(g) (a) State the meaning of the term catalyst. . …… . …… [2] (b) The diagram shows the equipment the student uses. cotton wool catalyst of manganese(IV) oxide aqueous hydrogen peroxide balance The student uses this method: ● the catalyst is added to the aqueous hydrogen peroxide ● the stop-clock is started ● the mass of the flask and contents is recorded at regular time intervals. A graph of the mass of the flask and contents against time is shown. mass of the flask and contents / g time / s (i) Suggest why the mass of the flask and contents decreases as time increases. . …… [1] (ii) Describe what happens to the rate of the reaction as time increases. . …… . …… [2] (c) The student repeats the experiment at a higher temperature. All other conditions stay the same. The rate of reaction increases. (i) Explain, in terms of collisions between particles, why the rate of reaction increases at a higher temperature. . …… . …… . …… . …… [3] (ii) Draw a line on the graph in (b) for the experiment at a higher temperature. [2] [Total: 10]

Question

(a) Ethanol is a member of the homologous series of alcohols. Give two characteristics of members of a homologous series. 1 . …… 2 . …… [2] (b) Ethanol can be manufactured from ethene. Ethene can be made from long chain hydrocarbons such as decane, C10H22. Ethene is then converted into ethanol. (i) Name the process used to obtain ethene from long chain hydrocarbons such as decane, C10H22. . …… [1] (ii) Complete the chemical equation to show the formation of ethene from decane, C10H22. C10H22 → C4H8 + …… + …… [2] (iii) Write the chemical equation for the conversion of ethene into ethanol. . …… [1] (iv) Name the type of reaction occurring when ethene is converted into ethanol. . …… [1] (v) Give one condition for the reaction in which ethene is converted into ethanol. . …… [1] (c) Ethanol can also be produced by fermentation of carbohydrates such as glucose. Give two advantages of manufacturing ethanol by fermentation compared to manufacturing ethanol from ethene. 1 . …… 2 . …… [2] (d) (i) Under certain conditions ethene can react with chlorine to produce chloroethene. The structure of chloroethene is shown. H H C C H Cl The equation for the chemical reaction is shown. C2H4 + Cl 2 → C2H3Cl + HCl State the type of chemical reaction between ethene and chlorine that this equation shows. . …… [1] (ii) Chloroethene monomers can be converted into a polymer called poly(chloroethene). State the type of polymerisation that produces poly(chloroethene) from chloroethene. . …… [1] (iii) Draw a section of the poly(chloroethene) molecule made from two monomer molecules. [2] (e) The structure of part of a polymer is shown. O O O N C N C N C H H H This polymer is made from one type of monomer only. Complete the diagram to show the structure of the monomer used to produce this polymer. Show all of the atoms and all of the bonds in the functional groups. [2] [Total: 16] 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.).