Chemistry 9701/22 October/November 2022: question paper and mark scheme

Question

Species such as NH4+, CO32– and PO43– are examples of molecular ions. (a) Ionic and covalent bonds both involve an electrostatic attraction between different species. Identify the species that are electrostatically attracted to one another in: ● an ionic bond . …… ● a covalent bond. . …… [2] (b) Complete Table 1.1 to show the total numbers of protons and electrons in the molecular ions NH4+, CO32– and PO43–. Table 1.1 molecular total number total number ion of protons of electrons NH4+ CO32– PO43– [3] (c) NH4+ is a Brønsted–Lowry acid. (i) Define Brønsted–Lowry acid. . …… . …… [1] (ii) When NH4+(aq) is heated with NaOH(aq), a pungent gas is produced. Write an ionic equation for this reaction. . …… [1] (iii) The nitrogen atom in NH4+ is sp3 hybridised. sp3 orbitals form from the mixing of one 2s and three 2p orbitals. Sketch the shapes of a 2s and a 2px orbital on the axes in Fig. 1.1. z z y y x x 2s 2px Fig. 1.1 [2] (d) There are many naturally occurring hydrated compounds that contain the anion PO43–. (i) Name the anion PO43–. . …… [1] (ii) Struvite is a soft hydrated mineral with Mr = 245.3. The anhydrous form of the mineral has the formula NH4MgPO4. Calculate the number of molecules of water of crystallisation in struvite. Give your answer to the nearest integer. Show your working. number of molecules of water of crystallisation = …… [2] (e) OH–(aq) reacts with 2-bromo-2-methylpropane in an SN1 reaction. The molecular ion (CH3)3C+ forms as the intermediate in this reaction. (i) Draw the mechanism for the SN1 reaction of OH– with 2-bromo-2-methylpropane. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. Draw the structures of the organic reactant and organic product. H 3C + CH3 C CH3 [3] (ii) 2-bromo-2-methylpropane is a tertiary bromoalkane. Define tertiary bromoalkane. . …… . …… [1] (iii) Organic compound M forms when 2‑bromo‑2‑methylpropane is heated with ethanolic OH–. Draw the structure of M. [1] [Total: 17]

Question

The chlorides of some of the Period 3 elements are shown in Table 2.1. Table 2.1 Period 3 chloride NaCl Al Cl 3 SiCl 4 PCl 5 PCl 3 SCl 2 bonding C C structure S S oxidation state of Period 3 element (a) Complete Table 2.1. ● Identify the bonding shown by each chloride under standard conditions. Use C = covalent, I = ionic, M = metallic. ● Identify the structure shown by each chloride under standard conditions. Use G = giant, S = simple. ● Deduce the oxidation state of the Period 3 element in each chloride. [4] (b) Write equations for the reactions of NaCl and PCl 5 with water. Include state symbols in both equations. NaCl …… PCl 5 …… [3] (c) In the gas phase, Al Cl 3(g) exists at equilibrium with Al 2Cl 6(g) as shown. equation 1 2Al Cl 3(g) Al 2Cl 6(g) ∆Hr = –63 kJ mol–1 (i) Complete the dot-and-cross diagram to show the bonding in Al 2Cl 6. Cl Al Cl [2] (ii) State the effect of an increase in temperature on the equilibrium mixture in equation 1. Explain your answer. . …… . …… [1] (d) A 3.30 g sample of a Period 3 chloride is heated to 500 K in a sealed flask. At this temperature, the chloride is a gas of volume 250 cm3 and the pressure in the flask is 323 kPa. Use the ideal gas equation pV = nRT to calculate the Mr of the Period 3 chloride. Deduce its formula. Mr = …… formula of Period 3 chloride = …… [3] (e) (i) An excess of Cl –(aq) is added to 1 cm3 of Br2(aq). Describe what is observed. Explain your answer. . …… . …… . …… [2] (ii) SCl 2 has Mr = 103.1 and is a liquid at room temperature. SBr2 has Mr = 191.9 and is a gas at room temperature. Explain the difference in the physical state of SCl 2 and SBr2. Give your answer in terms of intermolecular forces. . …… . …… . …… . …… [2] (f) Bismuth is a dense metal in the same group as phosphorus. (i) Draw a labelled diagram to show the bonding in bismuth metal. [2] (ii) Bismuth reacts with chlorine to form BiCl 3. BiCl 3 is a solid at room temperature. It melts when heated gently. BiCl 3 reacts vigorously with water at room temperature to form an acidic solution. Suggest the type of bonding and structure shown by BiCl 3. Explain your answer. . …… . …… . …… [2] [Total: 21]

Question

Organic compounds can be distinguished using chemical tests and analytical techniques. (a) Table 3.1 shows four pairs of organic compounds. Table 3.1 positive result of organic compounds reagent chemical test on identified compound A1 A2 O O H B1 B2 O O C1 C2 O O O D1 D2 CH3 OH OH (i) Complete Table 3.1 to: ● identify a reagent which can distinguish between the compounds in each pair ● give the positive result of the chemical test and identify which compound shows this result. Use a different reagent for each test. [8] (ii) A1 and A2 are structural isomers. Define structural isomers. . …… . …… [1] (iii) Give the systematic name of B2. . …… [1] (iv) Deduce the molecular formula of D1. . …… [1] (b) D2 forms polymer Z when heated gently. (i) Identify the type of polymer that forms from D2. . …… [1] (ii) Draw one repeat unit of polymer Z. [2] (c) Organic compound E contains three carbon atoms. E reacts with cold dilute acidified KMnO4(aq) to form a single compound F with Mr = 154.9. Fig. 3.1 shows the infrared spectrum of E. Fig. 3.2 shows the infrared spectrum of F. E 100 transmittance /% 50 0 4000 3000 2000 1500 1000 500 wavenumber / cm–1 Fig. 3.1 F 100 transmittance /% 50 0 4000 3000 2000 1500 1000 500 wavenumber / cm–1 Fig. 3.2 Table 3.2 bond functional group containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=C aromatic compound, alkene 1500–1680 C=O amide 1640–1690 carbonyl, carboxyl 1670–1740 ester 1710–1750 C≡N nitrile 2200–2250 C–H alkane 2850–3100 N–H amine, amide 3300–3500 O–H carboxyl 2500–3000 hydroxy 3200–3650 Both spectra show absorptions between 2850 and 2950 cm–1 owing to C–H bonds in each molecule. (i) Use the two infrared spectra and Table 3.2 to identify the functional group present only in E. Explain your answer, referring only to absorptions at frequencies greater than 1500 cm–1. functional group …… explanation …… . …… [1] (ii) Use the infrared spectrum of F to identify the functional group formed when E reacts with cold dilute acidified KMnO4(aq). Explain your answer, referring only to absorptions at frequencies greater than 1500 cm–1. functional group …… explanation …… . …… [1] (iii) The mass spectrum of E shows a molecular ion peak and an M+2 peak of approximately equal abundance at m/e = 120 and 122. Deduce the relative molecular mass, Mr, of E. Mr = …… [1] (iv) Use the information in 3(c) to suggest a structure for E. [1] (v) Complete the equation for the reaction of E with cold dilute acidified KMnO4(aq) to form F. In the equation, [O] represents cold dilute acidified KMnO4(aq). H2O + [O] + …… → . …… [1] (d) C2 can be synthesised using A1 as a single organic reactant. A1 C2 O O H O Devise a multi-step synthetic route to form C2 from A1. Identify relevant reagents and conditions, and state the organic products of each step. . …… . …… . …… . …… . …… . …… [3] [Total: 22] Important values, constants and standards molar gas constant R = 8.31 J K–1 mol–1 Faraday constant F = 9.65 × 104 C mol–1 Avogadro constant L = 6.022 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 at s.t.p. (101 kPa and 273 K) Vm = 24.0 dm3 mol–1 at room conditions ionic product of water Kw = 1.00 × 10–14 mol2 dm–6 (at 298 K (25 °C)) specific heat capacity of water c = 4.18 kJ kg–1 K–1 (4.18 J g–1 K–1) The Periodic Table of Elements Group 1 2 13 14 15 16 17 18 1 2 H He hydrogen helium Key 1.0 4.0 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 6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon 23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 at www.cambridgeinternational.org after the live examination series. 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 39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 16 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 85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 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 132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – – 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 138.9 140.1 140.9 144.4 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0 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 – 232.0 231.0 238.0 – – – – – – – – – – – Assessment International Education Copyright Acknowledgements Booklet. 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