Chemistry 9701/23 May/June 2024: question paper and mark scheme

Question

(a) (i) Explain the lack of reactivity of nitrogen gas, N2(g). …… [2] (ii) Covalent bonds can be σ bonds or π bonds. Complete Table 1.1 to show the number of σ and π bonds in a molecule of N2 and to describe how the orbitals overlap to form σ and π bonds. Table 1.1 σ bond π bond number of bonds in N2 how the orbitals overlap [4] (b) (i) A sample of Al reacts with an excess of Cl 2. State the oxidation number of Al in the product of the reaction. oxidation number of Al …… [1] (ii) State what determines the maximum oxidation number of the Period 3 elements in their oxides. …… [1] (c) Separate samples of aluminium oxide, Al 2O3, and phosphorus(V) oxide, P4O10, react with an excess of NaOH(aq) at room temperature. (i) Give the state of Al 2O3 and P4O10 at room temperature. Al 2O3 …… P4O10 …… [1] (ii) Write an equation for the reaction of each oxide with an excess of NaOH(aq) at room temperature. Al 2O3 + …… P4O10 + …… [2] (d) The oxide of silicon reacts with calcium oxide in an addition reaction to produce calcium silicate, CaSiO3. The oxidation number of calcium in CaSiO3 is +II. (i) Deduce the oxidation number of silicon in calcium silicate. oxidation number of silicon …… [1] (ii) Calcium oxide can be made from calcium carbonate in a single-step reaction. Identify the type of reaction that occurs. …… [1] [Total: 13]

Question

N2(g) reacts with H2(g) in the Haber process, as shown in reaction 1. reaction 1 N2(g) + 3H2(g) 2NH3(g) ΔH = –x kJ mol–1 Table 2.1 shows the different conditions used to produce three equilibrium mixtures, A, B and C. Table 2.1 A B C initial molar ratio of N2 : H2 added 1:3 1:3 1:3 temperature / °C 500 500 1000 pressure / atm 1000 1000 1000 iron present in mixture no yes no percentage yield of NH3(g) at equilibrium 58 x y (a) Describe and explain the change, if any, to the percentage yield of NH3(g) produced in B compared to A. …… [1] (b) (i) Describe and explain the change, if any, to the percentage yield of NH3(g) produced in C compared to A. …… [1] (ii) Describe and explain the change to the rate of the forward reaction that occurs to establish the equilibrium in C compared to A. You do not need to refer to the Boltzmann distribution in your answer. …… [2] (c) (i) Write an expression for the equilibrium constant, Kp, for reaction 1. State the units. Kp = units …… [2] (ii) Equilibrium mixture D is made when 1.0 mol of N2(g) and 3.0 mol of H2(g) are added to a sealed container at 750 °C and 1000 atm and left to reach equilibrium. This mixture contains 1.16 mol of NH3(g). Calculate the mole fraction of NH3(g) in D. mole fraction of NH3(g) = …… [2] (iii) The mole fraction of N2(g) is 0.625 in a new equilibrium mixture, E. Calculate the partial pressure of N2(g) in E when the total pressure is 1000 atm. partial pressure of N2(g) = …… atm [1] (d) When oxides of nitrogen escape into the atmosphere they may be involved in: • formation of acid rain from sulfur dioxide • formation of photochemical smog. (i) Identify the role of NO and NO2 in the formation of H2SO4 from SO2 in the atmosphere to produce acid rain. Use relevant equations to support your answer. …… [3] (ii) Outline how NO and NO2 may contribute to the formation of photochemical smog. …… [2] [Total: 14]

Question

(a) Write an equation to show the reaction for the standard enthalpy change of formation of H2O. Include state symbols. …… [2] (b) Water is one of the products in the reaction of B2O3 and NH3, as shown in reaction 2. reaction 2 B2O3 + 2NH3 2BN + 3H2O Table 3.1 shows information about the standard enthalpy change of formation, ΔH of , of some substances. Table 3.1 substance ΔH of / kJ mol–1 B2O3 –1264 NH3 – 46 BN –134 H2O –286 Calculate the enthalpy change, ∆H, for reaction 2 using the data from Table 3.1. ∆H = …… kJ mol–1 [2] (c) Boron carbide is a hard crystalline solid that has a melting point greater than 2000 °C. (i) Suggest the structure and bonding in boron carbide. …… [1] (ii) 100 g of pure boron carbide contains 78.26 g of boron. Calculate the empirical formula of boron carbide. Show your working. empirical formula of boron carbide …… [2] [Total: 7]

Question

(a) NH3(g) reacts with HCl (g) to produce NH4Cl (s), as shown. NH3(g) + HCl (g) NH4Cl (s) Draw a diagram to show the ionic, covalent and coordinate bonding present in a formula unit of NH4Cl . [2] (b) An exothermic reaction occurs when NH4+(aq) is added to OH–(aq). (i) Identify the type of reaction. …… [1] (ii) Construct an ionic equation for the reaction of NH4+ and OH–. …… [1] (c) Substitution reactions of NH3 and OH– with halogenoalkanes both involve a lone pair of electrons. (i) Name the role of NH3 and OH– in these reactions. …… [1] (ii) Suggest which species, NH3 or OH–, is more reactive during these reactions. Explain your answer. …… [1] (d) When 2-bromo-2-methylpropane reacts with OH–, two mechanisms, SN1 and SN2, both occur. The SN2 mechanism has a slower rate. Fig. 4.1 shows the reaction pathway diagram for the SN1 mechanism. Sketch a graph on Fig. 4.1 to show the reaction pathway for the SN2 mechanism. reactants energy / kJ mol-1 intermediate products progress of reaction Fig. 4.1 [2] (e) (i) Complete Fig. 4.2 to show the mechanism for the SN1 reaction that occurs when CH3CHBrC2H5 reacts with NH3 to produce CH3CH(NH2)C2H5. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. H H H H Br C C2H5 C+ C2H5 H N+ C C 2H5 CH3 CH3 H CH3 H H2N C C2H5 CH3 Fig. 4.2 [3] (ii) Identify the inorganic product that forms in the reaction in Fig. 4.2. …… [1] (iii) Give the systematic name for the organic product CH3CH(NH2)C2H5. …… [1] (f) (i) Complete Table 4.1 by drawing the structural formula of the intermediate that is formed when 2-bromo-2-methylpropane reacts in an SN1 reaction. Table 4.1 2-bromobutane 2-bromo-2-methylpropane H structural formula of intermediate in SN1 C+ C 2H5 reaction CH3 [1] (ii) Identify the halogenoalkane in Table 4.1 that has the greater tendency to react using the SN1 mechanism. Explain your answer. …… [2] [Total: 16]

Question

(a) M reacts to form R by the addition of one reagent, as shown in Fig. 5.1. M R HO reagent HO Fig. 5.1 Identify the reagent and conditions for this reaction. …… [1] (b) R is also made from M by two steps, as shown in Fig. 5.2. M Q R Br HO step 1 step 2 Br HO Fig. 5.2 (i) Identify the reagents and conditions for steps 1 and 2 in Fig. 5.2. step 1 …… step 2 …… [2] (ii) Name the mechanism for step 1 in Fig. 5.2. …… [1] (c) The infrared spectrum of R is shown in Fig. 5.3. 100 80 transmittance 60 /% 40 20 0 4000 3500 3000 2500 2000 1500 1000 500 wavenumber / cm–1 Fig. 5.3 Table 5.1 bond functional groups 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 2850–2950 N–H amine, amide 3300–3500 O–H carboxyl 2500–3000 hydroxy 3200–3650 Use the absorptions in the region above 1500 cm–1 in Table 5.1 when answering this question. • Add F to Fig. 5.3 to identify the peak that is present in an infrared spectrum of both Q and R. Identify the bond that corresponds to the absorption for F. • Add G to Fig. 5.3 to identify the peak that is not present in an infrared spectrum of Q. Identify the bond that corresponds to the absorption for G. [2] (d) Y is made from Q in a three-step reaction. Q W X OH Br O step 1 step 2 HO Br KCN in O ethanol / heat step 3 reducing agent Z Y OH HO Fig. 5.4 (i) Draw the structure of W in the box in Fig. 5.4. [1] (ii) In step 2, W is heated with HCl (aq) to produce X and an inorganic product. Identify the formula of the inorganic product. …… [1] (iii) In step 3, X reacts with reducing agent Z to produce Y. Complete the equation for the reaction of X with Z. Use a molecular formula to represent the organic product. Use [H] to represent one atom of hydrogen from Z. …… C8H12O4 + ……[H] …… [1] (iv) Identify Z. …… [1] [Total: 10] 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 138.9 140.1 140.9 144.2 – 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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