Chemistry 9701/24 October/November 2025: question paper and mark scheme

Question

The Group 17 elements are oxidising agents. (a) (i) Explain how the Group 17 elements act as oxidising agents. …… [1] (ii) Write an equation to show the reaction in which Cl 2 oxidises aluminium metal. …… [1] (iii) A student heats equal amounts of I2(g) and H2(g) in a sealed flask. The student leaves the contents to cool. State what you would observe during the reaction. …… [1] (b) Cl 2 and Br2 can each react with NH3 to give N2 and a hydrogen halide, HX. 3X2 + 2NH3 N2 + 6HX X = Cl or Br The relative bond strengths of X–X and H–X determine the difference in enthalpy change of the two reactions. (i) Describe and explain the difference in the X–X bond strengths of Cl 2 and Br2. …… [2] (ii) Describe the relative thermal stabilities of HCl and HBr. …… [1] * 0000800000003 * DFD 3 (iii) Define enthalpy change of formation, ΔHf. …… [2] (iv) Table 1.1 gives data relevant to the reaction of Cl 2(g) with NH3(g). Table 1.1 enthalpy change of compound formation, ΔHf / kJ mol–1 NH3(g) – 46 HCl (g) –92 Use the data in Table 1.1 to calculate the enthalpy change of the reaction of Cl 2(g) with NH3(g). enthalpy change of reaction = …… kJ mol–1 [2] (v) I2 reacts with NH3 to form NI3. Predict the shape of a molecule of NI3. Explain your answer. shape …… explanation …… [2] * 0000800000004 * DFD 4 (c) Table 1.2 shows some information about reactions of NaCl , NaBr and NaI. Table 1.2 NaCl NaBr NaI observation white precipitate with Ag+(aq) type of reaction with acid–base acid–base, then redox acid–base, then redox concentrated H2SO4 • black solid observations with • yellow solid concentrated H2SO4 • effervescence (i) Complete Table 1.2. [4] (ii) Suggest an identity for the species that produces each observation in the reaction of NaI with concentrated H2SO4. black solid …… yellow solid …… effervescence …… [2] (d) Table 1.3 gives some information about MgCl 2 and SiCl 4. Table 1.3 MgCl 2 SiCl 4 electrical conductivity when liquid conducts does not conduct observation when added to water dissolves vigorous reaction (i) Explain the difference between the electrical conductivity of liquid MgCl 2 and of liquid SiCl 4. Refer to bonding and relevant particles in your answer. …… [2] (ii) Suggest the pH of the solutions that form when each chloride is added to water. MgCl 2 …… SiCl 4 …… [2] [Total: 22] * 0000800000005 * DFD 5 * 0000800000006 * DFD 6

Question

Aluminium oxide, Al 2O3, and phosphorus(V) oxide, P4O10, are both used as reagents and catalysts. (a) The melting point of Al 2O3 is 2072 °C. The melting point of P4O10 is 340 °C. Explain the difference in the melting points of these two compounds. …… [3] (b) A 5.00 dm3 sealed flask contains 0.400 mol of CO(g) and 0.800 mol of H2(g) and an Al 2O3 catalyst. The flask is heated to a temperature of 290 °C and allowed to reach equilibrium. Equation 1 shows the reaction. equation 1 CO(g) + 2H2(g) CH3OH(g) The equilibrium constant, Kc, of equation 1 is given. [CH3OH] Kc = [CO][H2]2 (i) State the units of Kc. …… [1] (ii) The equilibrium mixture contains 0.280 mol of CH3OH(g). Calculate the value of Kc. Give your answer to three significant figures. value of Kc = …… [3] (iii) State and explain the effect, if any, on the value of Kc when the overall pressure in the sealed flask is increased. …… [1] * 0000800000007 * DFD 7 (c) P4O10 catalyses the reversible reaction of CO with H2 to form CH3OH. equation 1 CO(g) + 2H2(g) CH3OH(g) P4O10 then acts as a dehydrating agent, causing CH3OH to form CH3OCH3. (i) Explain how the presence of a catalyst affects a chemical reaction. …… [1] (ii) Construct an equation for the dehydration reaction of CH3OH to form CH3OCH3. …… [1] (iii) Write an equation to show the reaction of P4O10 with an excess of water. …… [1] [Total: 11] * 0000800000008 * DFD 8

Question

Propan-2-ol, (CH3)2CHOH, is sometimes added to fuel to help it burn. Fig. 3.1 shows some reactions of propan-2-ol. propan-2-ol reaction 3 reaction 1 OH concentrated acidified K2Cr2O7 H2SO4 L K alkaline reaction 2 I2(aq) CH3CO2– and CHI3 Fig. 3.1 (a) (i) Draw the structure of organic compound K. [1] (ii) State an observation you would make in reaction 2. …… [1] (iii) State the type of reaction that is shown in reaction 3. …… [1] (iv) Complete Fig. 3.2 to show the pi (π) bond in L that is formed from orbital overlap. H H C C H3C H Fig. 3.2 [1] * 0000800000009 * DFD 9 (b) Propan-2-ol reacts with sodium to produce (CH3)2CH–O – anions. These anions react with 2-bromopropane to form compound N, as shown in Fig. 3.3. N Br (CH3)2CH–O– O Fig. 3.3 (i) Write an equation for the reaction of propan-2-ol with sodium. …… [1] (ii) The reaction of 2-bromopropane with (CH3)2CH–O – anions follows an SN1 mechanism. Complete Fig. 3.4 to show this mechanism. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. H H H H3C C Br H 3C C O C CH3 CH3 CH3 CH3 (CH3)2CH–O– Fig. 3.4 [3] (iii) Suggest how the rate of the SN1 reaction would change, if at all, if 2-chloropropane were used instead of 2-bromopropane. Explain your answer. …… [2] (iv) N is also added to petrol to make it burn more smoothly. Construct an equation for the complete combustion of N, C6H14O. C6H14O …… [1] [Total: 11] * 0000800000010 * DFD 10

Question

Compounds P and Q are structural isomers. P Q Fig. 4.1 (a) (i) Define structural isomerism. …… [2] (ii) P shows geometrical isomerism. Draw the geometrical isomer of P. Explain why the two isomers are not identical. geometrical isomer of P explanation …… [2] (iii) Both P and Q react with aqueous bromine. Name the mechanism of this reaction. …… [1] (iv) Q is oxidised by hot concentrated acidified KMnO4(aq), forming two different organic products. Construct an equation for this reaction. Use [O] to represent an atom of oxygen from the oxidising agent. (CH3)2C=CHCH3 …… [2] * 0000800000011 * DFD 11 (v) Q reacts with HBr(g) to produce two structural isomers, R and S, as shown in Fig. 4.2. Q R S HBr(g) and Br Br Fig. 4.2 State and explain why isomer S is the major product of the reaction. …… [2] (vi) The mass spectrum of R shows peaks at m / e = 150 and m / e = 152. Suggest structures for the ions responsible for these peaks. peak at m / e = 150 peak at m / e = 152 [2] * 0000800000012 * DFD 12 (b) Fig. 4.3 shows a synthesis starting from T, a different isomer of R and S. T U V reaction 1 reaction 2 HCl (aq) Br CN COOH Fig. 4.3 (i) Identify the reagent and conditions for reaction 1. …… [1] (ii) Reaction 2 is a hydrolysis reaction. Construct an equation for reaction 2. (C2H5)2CHCN …… [1] (iii) V reacts with propan-2-ol in the presence of a catalytic amount of H2SO4 to form organic compound W. Complete Table 4.1 to give details of this reaction. Table 4.1 reaction of V with propan-2-ol type of reaction functional group formed molecular formula of organic product W [3] DFD 13 DFD 14 * 0000800000015 * DFD 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 = 6.02 × 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 DFD 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. 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