Chemistry 9701/22 February/March 2025: question paper and mark scheme

Question

Phosphorus and chlorine are elements in Period 3 of the Periodic Table. (a) Chlorine forms three different compounds with phosphorus. The most common compounds are PCl 3 and PCl 5. (i) Complete Table 1.1. Table 1.1 compound oxidation number of P oxidation number of Cl PCl 3 PCl 5 [2] (ii) In a closed system, PCl 3 and PCl 5 exist in an equilibrium mixture as shown in reaction 1. reaction 1 PCl 3(l) + Cl 2(g) PCl 5(s) ΔH = –124 kJ mol–1 Deduce two conditions that favour the production of PCl 5 in reaction 1. 1 …… 2 …… [2] (iii) The third compound of phosphorus and chlorine, W, has a relative molecular mass, Mr, between that of PCl 3 and PCl 5. The compound contains 69.6% by mass of chlorine. Determine the molecular formula of W. molecular formula of W = …… [2] (iv) W is a liquid at room temperature and pressure. It reacts vigorously with water to form an acidic solution. Suggest the structure and bonding in W. Explain your answer. …… [2] (b) Fig. 1.1 shows a reaction scheme involving P4 and Cl 2. Cl 2(g) C Cl P4 PCl 5 Cl reaction 2 reaction 6 excess O2(g) H2O reaction 3 reaction 4 H2 O A(s) B(aq) reaction 5 Fig. 1.1 (i) Suggest what is observed in reaction 2. …… [1] (ii) Predict the shape of a molecule of PCl 5. …… [1] (iii) Write an equation for the formation of A in reaction 3. …… [1] (iv) Name B, which is formed in both reactions 4 and 5. …… [1] (v) Draw the structure of C, used in reaction 6. [1] (c) 1,2-dichloroethane, Cl CH2CH2Cl, reacts with NaOH to produce an unsaturated compound, C2H3Cl, as shown in reaction 7. reaction 7 Cl CH2CH2Cl + NaOH C2H3Cl + H2O + NaCl (i) State what is meant by unsaturated. …… [1] (ii) State the conditions for reaction 7. …… [1] (d) Compound D contains carbon, hydrogen and chlorine only. Fig. 1.2 shows the mass spectrum of D. 1 100 80 60 abundance / % 40 2 20 0 20 30 40 50 60 m/e Fig. 1.2 (i) Explain the relative abundance of peaks 1 and 2 in the mass spectrum in Fig. 1.2. …… [1] (ii) Suggest the structure of D. [1] [Total: 17]

Question

(a) The Group 2 elements show metallic bonding. Define metallic bonding. …… [2] (b) The Group 2 elements form stable 2+ cations. (i) State and explain the variation in ionic radius of the Group 2 elements down the group. …… [2] (ii) Table 2.1 shows successive ionisation energy values for beryllium, Be. Table 2.1 1st 2nd 3rd 4th ionisation energy / kJ mol–1 900 1760 14 800 21 000 Use Table 2.1 to state and explain: • the general trend in these values • the significance of the large difference between the 2nd and 3rd ionisation energies. …… [2] (c) All the Group 2 elements except beryllium have more than one stable isotope. (i) Beryllium exists as the single isotope 94Be. Describe the distribution of mass within an atom of 94Be. …… [2] (ii) Complete Table 2.2 to show the numbers of protons and neutrons in the isotopes of magnesium. Table 2.2 isotope number of protons number of neutrons magnesium-24 magnesium-25 magnesium-26 [2] (iii) Fig. 2.1 shows the behaviour of a beam of protons in an electric field. Complete Fig. 2.1 to show the behaviour of separate beams of neutrons and electrons in the same electric field. Label your diagram clearly. Assume that the beams of each particle are moving at the same velocity. source Fig. 2.1 [3] (d) (i) State what is observed when dilute hydrochloric acid is added to separate samples of barium oxide and barium carbonate. barium oxide …… barium carbonate …… [2] (ii) Write an equation for the reaction of strontium, Sr, with an excess of cold water. …… [1] (iii) State the variation in solubility of the Group 2 sulfates down the group. …… [1] [Total: 17]

Question

The halogens chlorine, bromine and iodine show trends in chemical and physical properties down the group. Table 3.1 shows some properties of chlorine, bromine and iodine. Table 3.1 property chlorine bromine iodine colour and state at room temperature green gas bond energy / kJ mol–1 242 193 151 electronegativity 3.0 2.8 2.5 formula of sodium halide NaCl NaBr NaI (a) (i) Complete Table 3.1. [1] (ii) The bond energy values in Table 3.1 refer to the X—X bond where X is the halogen. Explain the trend in the bond strength of the X—X bond in the halogens. …… [2] (b) Explain, with the use of an equation, how chlorine, Cl 2, is used in water purification. State the role of the active species produced. …… [2] (c) The sodium halides in Table 3.1 also show trends in chemical properties. (i) Identify the sodium halide that reacts with concentrated H2SO4 to form H2S. …… [1] (ii) Identify the sodium halide that only undergoes a Brønsted–Lowry acid–base reaction with concentrated H2SO4. …… [1] (iii) A student adds a few drops of AgNO3(aq) to a solution of NaBr(aq). State what is observed. …… [1] (d) Iodine monobromide, IBr, is a dark red solid that melts near room temperature. IBr reacts with propene. The mechanism for this reaction is the same as the mechanism for that of HBr with propene. (i) Identify all the intermolecular forces that exist between molecules of IBr. …… [1] (ii) Name the mechanism involved in the reaction of IBr with propene. …… [1] (iii) The reaction of IBr with propene forms two structural isomers. Draw the two structural isomers shown by these molecules. [2] (iv) Identify the type of structural isomerism shown by the molecules in (d)(iii). …… [1] (v) Explain why the two structural isomers do not form in equal amounts. …… [2] [Total: 15]

Question

Fig. 4.1 shows compounds J to M, each of which contains four carbon atoms. J K L M O O OH O H OH Fig. 4.1 (a) Table 4.1 gives details of tests on J to M. In each test, only two compounds give a positive result. Complete Table 4.1. Table 4.1 observation of positive compounds that give a reagent result positive result acidified K2Cr2O7(aq) J and L alkaline I2(aq) yellow precipitate orange precipitate J and K Na(s) [5] (b) K reacts with HCN in the presence of a KCN catalyst, forming N. (i) Complete Fig. 4.2 to show the mechanism for this reaction. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. K N O OH C H3C C C 2H5 H3C C 2H 5 CN CN Fig. 4.2 [4] (ii) Identify the class of compound of which N is a member. …… [1] (iii) N has a chiral centre. Explain what is meant by a chiral centre. …… [1] [Total: 11] 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 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 12 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