Chemistry 0620/41 October/November 2023: question paper and mark scheme

Question

A list of gases is shown. ammonia carbon dioxide carbon monoxide ethene fluorine oxygen sulfur dioxide xenon Answer the following questions using only the gases from the list. Each gas may be used once, more than once or not at all. Give the name of the gas that: (a) causes acid rain . …… [1] (b) forms an alkaline solution when dissolved in water . …… [1] (c) is inert . …… [1] (d) is a product of photosynthesis . …… [1] (e) can form a polymer . …… [1] (f) is produced in the test for nitrate ions. . …… [1] [Total: 6]

Question

Boron and aluminium are Group III elements. (a) Boron has only two naturally occurring isotopes, 10B and 11B. Complete Table 2.1 to show the numbers of protons, neutrons and electrons in an atom of 11B. Table 2.1 number of protons number of neutrons number of electrons [2] (b) The relative atomic mass of boron to one decimal place is 10.8. (i) Determine the relative abundance of 10B present in boron. Give your answer as a percentage. …… % [1] (ii) Use the relative atomic mass of boron to calculate the number of atoms in 0.540 g of boron. Give your answer in standard form. number of atoms = …… [2] (c) Aluminium is extracted from its purified ore as shown in Fig. 2.1. + power – supply wires anodes + + cathode electrolyte molten aluminium Fig. 2.1 (i) Name the ore of aluminium. . …… [1] (ii) The electrolyte contains aluminium oxide and one other substance. Name the other substance and explain why it is used. name . …… explanation …… . …… [2] (iii) Write the ionic half-equation for the reaction at the cathode. . …… [2] (iv) Explain why the anodes need frequent replacement. . …… . …… [2] (d) State two physical properties of aluminium that make it suitable for use in overhead electrical cables. 1 . …… 2 . …… [2] (e) Explain the apparent unreactivity of aluminium. . …… . …… [2] (f) Aluminium reacts with fluorine to form aluminium fluoride, Al F3, an ionic compound. (i) Write the symbol equation for this reaction. . …… [2] (ii) Complete Fig. 2.2 to show the electronic configuration of one aluminium ion and one fluoride ion. Show the charges on the ions. Al F Fig. 2.2 [3] [Total: 21]

Question

Order of reactivity can be determined by displacement reactions. (a) A student investigates the reactivities of four metals by carrying out a series of experiments. Each of the metals lead, manganese, silver and zinc are added separately to aqueous metal nitrates of the other metals. (i) Table 3.1 shows some of the results. Table 3.1 lead manganese silver zinc aqueous solution Pb Mn Ag Zn lead(II) nitrate ✓ manganese(II) nitrate silver nitrate ✓ ✓ ✓ zinc nitrate ✗ ✗ key ✓ = displacement reaction occurs ✗ = displacement reaction does not occur Complete Table 3.1 and place the four metals in their order of reactivity with the most reactive first. 1 …… most reactive 2 …… 3 …… 4 …… [3] (ii) Suggest why the metal nitrates and not the metal sulfates of these four metals are used as the aqueous solutions. . …… [1] (iii) Write the symbol equation for the reaction between zinc and silver nitrate. . …… [2] (b) The reactivity of Group VII elements can be investigated experimentally. A student bubbles chlorine gas into a test-tube containing aqueous potassium bromide. (i) Describe the colour change seen in the test-tube. from …… to …… [2] (ii) Complete the ionic equation for this reaction. Include state symbols. …… + ....Br –(aq) → …… + …… [3] (iii) The reactivity trend seen in Cl, Br and I applies to all the elements in Group VII. Use the Periodic Table to identify the Group VII element which cannot displace any other Group VII elements. . …… [1] [Total: 12]

Question

Aqueous hydrogen peroxide, H2O2, slowly forms water and oxygen at room temperature and pressure, r.t.p. This reaction is catalysed by manganese(IV) oxide. The equation is shown. 2H2O2(aq) → 2H2O(l) + O2(g) (a) State the test for oxygen gas. test . …… observations …… [1] (b) A student investigates the rate of formation of oxygen gas when manganese(IV) oxide is added to aqueous hydrogen peroxide. The volume of oxygen gas formed is measured at regular time intervals at r.t.p. The results are plotted onto the graph in Fig. 4.1. volume of oxygen gas 0 0 t1 t2 time Fig. 4.1 (i) State how the graph in Fig. 4.1 shows the rate of reaction at time t2, is lower than at time t1. . …… [1] (ii) Explain, using collision theory, why the rate of reaction at time t2 is lower than at time t1. . …… . …… . …… [2] (iii) On Fig. 4.1, sketch the graph obtained when the experiment is repeated using aqueous hydrogen peroxide at a higher temperature. All other conditions remain the same. [2] (c) Manganese(IV) oxide is added to 20 cm3 of aqueous hydrogen peroxide. The total volume of oxygen gas produced is 72 cm3 at r.t.p. 2H2O2(aq) → 2H2O(l) + O2(g) Calculate the concentration of the aqueous hydrogen peroxide in g / dm3 using the following steps. ● Calculate the number of moles of oxygen gas produced. …… mol ● Determine the number of moles of hydrogen peroxide which reacts. …… mol ● Calculate the concentration of aqueous hydrogen peroxide in mol / dm3. …… mol / dm3 ● Calculate the concentration of aqueous hydrogen peroxide in g / dm3. …… g / dm3 [5] (d) Suggest the identity of one other metal oxide which also catalyses this reaction. . …… [1] [Total: 12]

Question

Methane reacts with steam to produce hydrogen gas. CH4(g) + H2O(g) CO(g) + 3H2(g) ∆H = +200 kJ / mol The reaction takes place at 1000 °C and 100 kPa pressure. (a) The reaction is reversible and reaches an equilibrium in a closed system. State two features of an equilibrium. 1 . …… 2 . …… [2] (b) State and explain, in terms of equilibrium, what happens to the concentration of hydrogen when: (i) the pressure is increased . …… . …… [2] (ii) the temperature is increased . …… . …… [2] (iii) a catalyst is used. . …… . …… [2] (c) Methane is a greenhouse gas which contributes to global warming. (i) Name a greenhouse gas found in clean, dry air. . …… [1] (ii) Explain, in terms of thermal energy, how greenhouse gases cause global warming. . …… . …… . …… . …… . …… [3] [Total: 12]

Question

Ethanol is manufactured by two methods: method 1 fermentation of aqueous glucose method 2 catalytic addition of steam to an alkene. (a) Method 1 takes place at room temperature and pressure. State two other conditions needed in method 1. 1 . …… 2 . …… [2] (b) (i) State the typical temperature and pressure used in method 2. temperature …… °C pressure . …… kPa [2] (ii) Name the alkene used in method 2. . …… [1] (iii) State why the reaction in method 2 is referred to as an addition reaction. . …… [1] (c) The catalyst in method 2 is phosphoric acid, H3PO4. Dilute phosphoric acid is a weak acid which contains phosphate ions, PO43–. (i) State what is meant by the term acid. . …… [1] (ii) State the meaning of weak in the term weak acid. . …… [1] (iii) Determine the oxidation number of phosphorus in the PO43– ion. Show your working. oxidation number = …… [2] (d) Give one advantage of each method of production of ethanol. method 1 . …… method 2 . …… [2] (e) Ethanol can be converted to ethanoic acid by reacting it with an acidified oxidising agent. (i) Name the acidified oxidising agent. . …… [1] (ii) State, in terms of redox, what type of reagent ethanol is in this reaction. . …… [1] (f) Ethanoic acid reacts with calcium to form a salt and one other product. (i) Name the salt. . …… [1] (ii) Write the formula of the salt. . …… [1] (iii) Identify the other product. . …… [1] [Total: 17] 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 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson – – – – – – – – – – – – – – – – – 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.).