Chemistry 9701/21 May/June 2023: question paper and mark scheme

Question

Tellurium is an element in Group 16. The most common isotope of tellurium is 130Te. Its electronic configuration is [Kr] 4d10 5s2 5p4. (a) Complete Table 1.1. Table 1.1 number of number of nucleon number neutrons electrons 130Te [3] (b) Identify the sub-shell in an atom of Te that contains electrons with the lowest energy. …… [1] (c) Construct an equation to represent the first ionisation energy of Te. …… [1] (d) (i) The radius of Te ions decreases after each successive ionisation. State two factors that are responsible for the increase in the first six ionisation energies of Te. …… [2] (ii) Sketch a graph in Fig. 1.1 to show the trend in the first seven ionisation energies of Te. ionisation energy / kJ mol–1 0 0 1 2 3 4 5 6 7 successive ionisation Fig. 1.1 [2] (e) Te reacts with F2 at 150 °C to form TeFx. Molecules of TeFx are octahedral with bond angles of 90°. Explain why TeFx is octahedral with bond angles of 90°. …… [2] (f) TeFx reacts with water to form tellurium hydroxide and HF. The oxidation number of tellurium does not change during this reaction. (i) Construct an equation for the reaction of TeFx with water. …… [1] (ii) Name the type of reaction that occurs when TeFx reacts with water. …… [1] [Total: 13]

Question

A neutralisation reaction occurs when NaOH(aq) is added to H2SO4(aq). equation 1 2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l) (a) Define enthalpy change of neutralisation, ∆Hneut. …… [2] (b) An experiment is carried out to calculate ∆Hneut for the reaction between NaOH(aq) and H2SO4(aq). 100 cm3 of 1.00 mol dm–3 NaOH(aq) is added to 75 cm3 of 1.00 mol dm–3 H2SO4(aq) in a polystyrene cup and stirred. Results from the experiment are shown in Table 2.1. Table 2.1 initial temperature of NaOH(aq) / °C 20.0 initial temperature of H2SO4(aq) / °C 20.0 maximum temperature of mixture / °C 27.8 (i) Use equation 1 to calculate the amount, in mol, of H2SO4(aq) that is neutralised in the experiment. amount of H2SO4(aq) neutralised = …… mol [1] (ii) Calculate ∆Hneut using the results in Table 2.1. Include units in your answer. Assume that: • the specific heat capacity of the final solution is 4.18 J g–1 K–1 • 1.00 cm3 of the final solution has a mass of 1.00 g • there is no heat loss to the surroundings • full dissociation of H2SO4(aq) occurs • the experiment takes place at constant pressure. Show your working. ∆Hneut = …… units …… [3] (c) (i) Complete the equation for the reaction that occurs when a solution of Ba(OH)2 is added to aqueous sulfuric acid. Include state symbols. …… H2SO4(aq) + ……Ba(OH)2(aq) …… [2] (ii) Suggest why the enthalpy change of neutralisation cannot be determined using the addition of dilute sulfuric acid to aqueous barium hydroxide. …… [1] [Total: 9]

Question

Chlorine is a very reactive element. (a) Chlorine reacts with silicon to form silicon(IV) chloride. Describe the appearance of silicon(IV) chloride at room temperature and pressure. State its structure and bonding. appearance …… structure and bonding …… [2] (b) Samples of magnesium chloride and phosphorus(V) chloride are added to separate beakers of cold water. Complete Table 3.1. Ignore temperature changes when considering observations for these reactions. Table 3.1 magnesium chloride phosphorus(V) chloride appearance at room temperature one similarity in observation on addition to cold water one difference in observation on addition to cold water pH of final solution [4] (c) (i) State the reagent and conditions required for the formation of sodium chlorate(V) from Cl 2(g). …… [1] (ii) Explain why the reaction in (c)(i) is described as a disproportionation reaction. Your answer should refer to relevant species and their oxidation numbers. …… [1] (d) Chlorine reacts with methane in a series of reactions to produce chloroalkanes. (i) State the conditions required for chlorine to react with methane. …… [1] (ii) One of the products of the reaction is CH2Cl 2 which reacts further to produce CHCl 3. Complete Table 3.2 to show details of the mechanism that forms CHCl 3 from CH2Cl 2. Table 3.2 name of step equation initiation propagation CH2Cl 2 + Cl • termination CHCl 3 [3] (e) CHCl 3 and HF are used to form CHCl F2 in a substitution reaction. Construct an equation for this reaction. …… [1] (f) X is a product of the substitution reaction that occurs when CHCl F2 reacts with Br2. There is only one naturally occurring isotope of fluorine, 19F. The mass spectrum of X shows molecular ion peaks at m / e = 164, 166 and 168. Complete Table 3.3 to show all the molecular ions responsible for each peak. Table 3.3 m/e formulae of molecular ions 164 166 168 (CF237Cl 81Br)+ [2] [Total: 15]

Question

V is a colourless liquid. V HO O Fig. 4.1 (a) V reacts with an excess of LiAl H4 to form W. (i) Draw the structure of W in the box. W [1] (ii) Identify the role of LiAl H4 in the reaction with V. …… [1] (b) V reacts to form Z in a single reaction, as shown in Fig. 4.2. V Z HO HO OH O O OH Fig. 4.2 (i) Suggest the reagent and conditions needed to form Z from V. …… [1] (ii) Deduce the empirical formula of Z. …… [1] (iii) Complete Table 4.1 to show the number of sp2 and sp3 hybridised carbon atoms that are present in a molecule of V. Table 4.1 type of hybridisation sp2 sp3 number of carbon atoms in V [2] (c) Q contains the elements carbon, hydrogen and oxygen only. It is a saturated molecule with no branching in its carbon backbone. Q contains only one functional group. The relative molecular mass of Q is 88. No effervescence is seen when Na2CO3 is added to Q. Effervescence is seen when sodium is added to Q. Q reacts with alkaline I2(aq) to form a yellow precipitate. Draw the structure of Q in the box. Q [2] [Total: 8]

Question

(a) Molecule M is present in petrol, a fuel used in cars. M is a saturated, non-cyclic hydrocarbon. M contains eight carbon atoms. (i) Construct an equation for the complete combustion of M. …… [2] (ii) Describe how the composition of products differs when incomplete combustion of M occurs. …… [2] (b) When petrol is burned in an internal combustion engine, oxides of nitrogen are released into the atmosphere. Oxides of nitrogen are responsible for the formation of acid rain. (i) Suggest the conditions required for the production of oxides of nitrogen during combustion of M in an internal combustion engine. Use an appropriate equation in your answer. …… [2] (ii) Describe how acid rain is formed in the atmosphere in the presence of oxides of nitrogen and SO2. Identify the role of the oxides of nitrogen in this process. Include all relevant equations. …… [3] (iii) State one other type of air pollution that is caused by the production of oxides of nitrogen in an internal combustion engine. …… [1] (c) Biodiesel T is a fuel made from vegetable oil R. Fig. 5.1 shows the production of T from R in a two-step process. R L J O C H 2C O (CH2) CH3 O 8 O step 1 + C C HO (CH2) CH3 8 HC O (CH2) CH3 8 O C H 2C O (CH2) CH3 heat with G 8 step 2 + concentrated H2SO4 T O H3C C O (CH2) CH3 8 Fig. 5.1 (i) In step 1 all three ester groups in R react. Suggest a suitable reagent and conditions for step 1. …… [1] (ii) Draw the structural formula of J in the box in Fig. 5.1. [1] (iii) Name the type of reaction that occurs in step 2. …… [1] (iv) Name organic reagent G used in step 2. …… [1] (v) L is called decanoic acid. Use systematic nomenclature to deduce the name of T. …… [1] [Total: 15] 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. This is produced for each series of examinations and is freely available to download To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge