Chemistry 0620/43 May/June 2021: question paper and mark scheme

Question

Give the name of the process that is used: (a) to produce large molecules from monomers . …… [1] (b) to separate oxygen from liquid air . …… [1] (c) to make ethanol from glucose . …… [1] (d) to separate water from aqueous sodium chloride . …… [1] (e) to produce aluminium from aluminium oxide in molten cryolite . …… [1] (f) to separate the products of hydrolysis of long chain carbohydrates . …… [1] (g) to separate an aqueous solution from an undissolved solid. . …… [1] [Total: 7]

Question

Complete the table to: ● deduce the number of protons, electrons and neutrons in the boron atom and chloride ion shown ● identify the atom or ion represented by the final row. number of number of number of formula protons electrons neutrons 5B 11 5 17Cl 35 – 17 24 21 30 [Total: 5]

Question

Sodium reacts with fluorine to form sodium fluoride, NaF. (a) Write a chemical equation for this reaction. . …… [2] (b) Sodium fluoride is an ionic compound. Complete the diagram to show the electron arrangement in the outer shells of the ions present in sodium fluoride. Give the charges on both ions. Na F [3] (c) Aqueous sodium fluoride undergoes electrolysis. (i) State what is meant by the term electrolysis. . …… . …… [2] (ii) Name the products formed at the positive electrode (anode) and the negative electrode (cathode) when dilute aqueous sodium fluoride undergoes electrolysis. anode . …… cathode . …… [2] (d) Molten sodium fluoride undergoes electrolysis. (i) Name the products formed at the positive electrode (anode) and the negative electrode (cathode) when molten sodium fluoride undergoes electrolysis. anode . …… cathode . …… [2] (ii) Write the ionic half-equation for the reaction at the negative electrode (cathode). . …… [1] (e) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of fluorine, F2. Show the outer electrons only. F F [1] (f) The melting points and boiling points of fluorine and sodium fluoride are shown. melting point boiling point / °C / °C fluorine –220 –188 sodium fluoride 993 1695 (i) Deduce the physical state of fluorine at –195 °C. Use the data in the table to explain your answer. physical state . …… explanation …… . …… [2] (ii) Explain, in terms of structure and bonding, why sodium fluoride has a much higher melting point than fluorine. Your answer should refer to the: ● types of particle held together by the forces of attraction ● types of forces of attraction between particles ● relative strength of the forces of attraction. . …… . …… . …… . …… [3] [Total: 18]

Question

Hydrogen iodide, HI, decomposes into iodine and hydrogen. The reaction is reversible. 2HI(g) I2(g) + H2(g) colourless gas purple gas colourless gas A gas syringe containing a mixture of hydrogen iodide, iodine and hydrogen gases was sealed. After reaching equilibrium the mixture was a pale purple colour. equilibrium mixture of hydrogen iodide, iodine and hydrogen end sealed plunger (a) State what is meant by the term equilibrium. . …… . …… . …… [2] (b) The plunger of the gas syringe is pushed in. The position of equilibrium does not change. The colour of the gaseous mixture turns darker purple. The temperature remains constant. 2HI(g) I2(g) + H2(g) colourless gas purple gas colourless gas (i) Explain why the position of equilibrium does not change. . …… [1] (ii) Suggest why the colour of the gaseous mixture turns darker purple even though the position of equilibrium does not change. . …… [1] (c) The forward reaction is endothermic. (i) State what happens to the position of equilibrium when the temperature is decreased. . …… . …… [1] (ii) State what happens to the rate of the forward reaction and the rate of the backward reaction when the temperature of the mixture is decreased. rate of the forward reaction . …… rate of the backward reaction …… [2] [Total: 7]

Question

This question is about salts. (a) Salts that are soluble in water can be made by the reaction between insoluble carbonates and dilute acids. Zinc sulfate is soluble in water. You are provided with solid zinc carbonate, ZnCO3, and dilute sulfuric acid, H2SO4. Describe how you would make a pure sample of zinc sulfate crystals. Your answer should include: ● practical details ● how you would make sure that all the dilute sulfuric acid has reacted ● a chemical equation for the reaction. . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… . …… [5] (b) Some sulfates decompose when heated. When hydrated iron(II) sulfate is heated strongly, sulfur dioxide gas is given off. (i) Describe a test for sulfur dioxide. test . …… observations …… [2] (ii) Complete the equation for the decomposition of hydrated iron(II) sulfate. ……FeSO4•7H2O → Fe2O3 + SO2 + SO3 + ……H2O[2] (c) Some chlorides are hydrated. When hydrated barium chloride crystals, BaCl 2•xH2O, are heated they give off water. BaCl 2•xH2O(s) → BaCl 2(s) + xH2O(g) A student carries out an experiment to determine the value of x in BaCl 2•xH2O. step 1 Hydrated barium chloride crystals are weighed. step 2 The hydrated barium chloride crystals are then heated. step 3 The remaining solid is weighed. (i) Describe how the student can be sure that all the water is given off. . …… . …… . …… [2] (ii) In an experiment, 4.88 g of BaCl 2•xH2O is heated until all the water is given off. The mass of BaCl 2 remaining is 4.16 g. [Mr: BaCl 2, 208; H2O, 18] Determine the value of x using the following steps. ● Calculate the number of moles of BaCl 2 remaining. …… mol ● Calculate the mass of H2O given off. …… g ● Calculate the number of moles of H2O given off. …… mol ● Determine the value of x. x = …… [4] [Total: 15]

Question

This question is about metals. (a) Iron is extracted from its main ore in a blast furnace. waste gases air air slag A (i) Coke and iron ore are added at the top of the blast furnace. Name one other substance that is added at the top of the blast furnace. . …… [1] (ii) Name the substance that leaves the blast furnace at A. . …… [1] (iii) Iron ore is mainly iron(III) oxide, Fe2O3. Name a substance that reduces iron(III) oxide to iron in the blast furnace. . …… [1] (iv) Temperatures inside a blast furnace can reach 2000 °C. Name two substances that react together, in the blast furnace, to produce this high temperature. . …… [1] (v) Name two waste gases that leave the blast furnace. 1 . …… 2 . …… [2] (b) Zinc is extracted from zinc blende. (i) Name the main zinc compound that is present in zinc blende. . …… [1] (ii) When zinc is extracted, it is formed as a gas. The gaseous zinc is then converted into molten zinc. State the name of this physical change. . …… [1] (c) Name the alloy that contains zinc and copper only. . …… [1] (d) Copper has the following properties. ● It has a high melting point. ● It has a high density. ● It is a good conductor of electricity. ● It has variable oxidation states. ● It forms a basic oxide. ● It forms soluble salts. (i) Give two properties from the list in which copper differs from Group I elements. 1 . …… 2 . …… [2] (ii) Give two properties from the list in which copper is similar to Group I elements. 1 . …… 2 . …… [2] [Total: 13]

Question

Many organic compounds contain carbon, hydrogen and oxygen only. (a) An organic compound R has the following composition by mass. C, 69.77%; H, 11.63%; O, 18.60% Calculate the empirical formula of compound R. empirical formula = …… [2] (b) Compound S has the empirical formula CH2O and a relative molecular mass of 60. Calculate the molecular formula of compound S. molecular formula = …… [2] (c) Compounds T and V have the same molecular formula, C3H6O2. ● Compound T is an ester. ● ompound V contains a –COOH functional group. C (i) State the name given to compounds with the same molecular formula but different structures. . …… [1] (ii) Name the homologous series that V is a member of. . …… [1] (iii) Draw a structure of compound T. Show all of the atoms and all of the bonds. Name compound T. name . …… [3] (iv) Draw the structure of compound V. Show all of the atoms and all of the bonds. Name compound V. name . …… [2] (d) Ethanol can be produced from long chain alkanes such as decane, C10H22, in a two-step process. step 1 step 2 decane ethene ethanol For each of the two steps: ● name the type of chemical reaction that occurs ● write a chemical equation. step 1: decane to ethene type of reaction …… chemical equation . …… step 2: ethene to ethanol type of reaction …… chemical equation . …… [4] [Total: 15] 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.).