20 (2410U20-1) 20 10. The crystallisation of sodium ethanoate from a super-saturated solution is used to release heat in reusable hand warmers. (a) A super-saturated solution of sodium ethanoate was made by dissolving 320 g of hydrated sodium ethanoate (CH3COONa.3H2O) in 60 cm3 of hot water. It was then allowed to cool to room temperature, which was measured as 17 °C. A thermometer was added to the solution, which caused the sodium ethanoate to start crystallising. The temperature of the process was recorded every 30 seconds for 3 minutes. The results are shown below: Time / s Temperature / °C 0 17 30 27 60 35 90 41 120 40 150 39 180 38 © WJEC CBAC Ltd. (2410U20-1) Turn over. 21 21 Examiner only (i) Plot the results on the graph paper below. [2] Temperature / °C Time / s (ii) Use your graph to calculate the maximum temperature change for this crystallisation. [2] maximum temperature change = ........................................................ °C © WJEC CBAC Ltd. 22 (2410U20-1) 22 Examiner only (iii) Use the total mass of the sodium ethanoate solution and the temperature change from the graph to calculate the enthalpy change of crystallisation per mole of sodium ethanoate. Assume the density of water is 1.00 g cm–3 and the specific heat capacity of sodium ethanoate solution is 4.18 J K–1 g–1. Mr(CH3COONa.3H2O) = 136 [4] enthalpy change = ........................................................ kJ mol–1 (iv) Suggest a reason why the experimental enthalpy change is often lower than the theoretical enthalpy change. [1] (b) Sodium ethanoate can be made in a neutralisation reaction. Complete the following equation: [2] CO2 H2O CH3COONa + + + ......................................................................... ......................................................................... (c) The carboxylic acid used to produce sodium ethanoate can be produced using an oxidation reaction. (i) Name the reagents and give the expected observations. [2] © WJEC CBAC Ltd. (2410U20-1) Turn over. 23 23 Examiner only (ii) A student proposed that the apparatus below should be used to perform this oxidation reduction experiment. The teacher said that this would not work and would be unsafe. Draw a labelled diagram of the apparatus that should be used in this experiment. [3] END OF PAPER © WJEC CBAC Ltd. 16 24 (2410U20-1) 24 © WJEC CBAC Ltd. Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only (2410U20-1) 25 Examiner only Question number Additional page, if required. Write the question number(s) in the left-hand margin. © WJEC CBAC Ltd. 25 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE (2410U20-1) 26 © WJEC CBAC Ltd. 26 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE (2410U20-1) 27 © WJEC CBAC Ltd. 27 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE (2410U20-1) 28 © WJEC CBAC Ltd. 28 BE*(S22-2410U20-1A) © WJEC CBAC Ltd. GCE AS/A LEVEL 2410U20-1A FRIDAY, 27 MAY 2022 – AFTERNOON CHEMISTRY – AS unit 2 Data Booklet Avogadro constant NA = 6.02 × 1023 mol –1 molar gas constant R = 8.31 J mol –1 K –1 molar gas volume at 273 K and 1 atm Vm = 22.4 dm3 mol –1 molar gas volume at 298 K and 1 atm Vm = 24.5 dm3 mol –1 Planck constant h = 6.63 × 10 –34 J s speed of light c = 3.00 × 108 m s –1 density of water d = 1.00 g cm –3 specific heat capacity of water c = 4.18 J g –1 K –1 ionic product of water at 298 K Kw = 1.00 × 10 –14 mol 2 dm – 6 fundamental electronic charge e = 1.60 × 10 –19 C temperature (K) = temperature (°C) + 273 1 dm3 = 1000 cm3 1 m3 = 1000 dm3 1 tonne = 1000 kg 1 atm = 1.01 × 105 Pa Multiple Prefix Symbol 10 –9 nano n 10 –6 micro μ 10 –3 milli m Multiple Prefix Symbol 10 3 kilo k 10 6 mega M 10 9 giga G Z22-2410U20-1A (2410U20-1A) 2 © WJEC CBAC Ltd. 10 to 70 5 to 40 20 to 50 25 to 60 50 to 90 90 to 150 110 to 125 110 to 160 160 to 185 190 to 220 N C R C C C O C C R Cl or Br C O C R C O (carboxylic acid / ester) C R (aldehyde / ketone) O C R N R C 13C NMR chemical shifts relative to TMS = 0 Type of carbon Chemical shift, δ (ppm) Infrared absorption values Bond Wavenumber / cm –1 500 to 600 650 to 800 1000 to 1300 1620 to 1670 1650 to 1750 2100 to 2250 2800 to 3100 2500 to 3200 (very broad) 3200 to 3550 (broad) 3300 to 3500 C Br C Cl C O C C C O C N C H O H (carboxylic acid) O H (alcohol / phenol) N H Turn over. (2410U20-1A) 3 © WJEC CBAC Ltd. *variable figure dependent on concentration and solvent 1H NMR chemical shifts relative to TMS = 0 Type of proton Chemical shift, δ (ppm) 0.9 0.1 to 2.0 3.1 to 4.3 1.3 2.0 2.0 to 3.0 2.0 to 2.5 2.2 to 2.3 R CH3 R CH2 R CH3 C N CH3 C O CH3 CH3 CH2 C O 4.5 * 4.5 to 6.3 6.5 to 7.5 6.5 to 8.0 R OH 3.3 to 4.3 HC Cl or HC Br C CH HC O C CH H 7.0 * OH 9.8 * 11.0 * R C O H R C O OH 5.8 to 6.5 C CH CO (2410U20-1A) 4 © WJEC CBAC Ltd. 6.94 Li Lithium 3 9.01 Be Beryllium 4 10.8 B Boron 5 12.0 C Carbon 6 14.0 N Nitrogen 7 16.0 O Oxygen 8 19.0 F Fluorine 9 20.2 Ne Neon 10 23.0 Na Sodium 11 24.3 Mg Magnesium 12 27.0 Al Aluminium 13 28.1 Si Silicon 14 31.0 P Phosphorus 15 32.1 S Sulfur 16 35.5 Cl Chlorine 17 40.0 Ar Argon 18 39.1 K Potassium 19 40.1 Ca Calcium 20 45.0 Sc Scandium 21 47.9 Ti Titanium 22 50.9 V Vanadium 23 52.0 Cr Chromium 24 54.9 Mn Manganese 25 55.8 Fe Iron 26 58.9 Co Cobalt 27 58.7 Ni Nickel 28 63.5 Cu Copper 29 65.4 Zn Zinc 30 69.7 Ga Gallium 31 72.6 Ge Germanium 32 74.9 As Arsenic 33 79.0 Se Selenium 34 79.9 Br Bromine 35 83.8 Kr Krypton 36 85.5 Rb Rubidium 37 87.6 Sr Strontium 38 88.9 Y Yttrium 39 91.2 Zr Zirconium 40 92.9 Nb Niobium 41 95.9 Mo Molybdenum 42 98.9 Tc Technetium 43 101 Ru Ruthenium 44 103 Rh Rhodium 45 106 Pd Palladium 46 108 Ag Silver 47 112 Cd Cadmium 48 115 In Indium 49 119 Sn Tin 50 122 Sb Antimony 51 128 Te Tellurium 52 127 I Iodine 53 131 Xe Xenon 54 133 Cs Caesium 55 137 Ba Barium 56 139 La Lanthanum 57 179 Hf Hafnium 72 181 Ta Tantalum 73 184 W Tungsten 74 186 Re Rhenium 75 190 Os Osmium 76 192 Ir Iridium 77 195 Pt Platinum 78 197 Au Gold 79 201 Hg Mercury 80 204 Tl Thallium 81 207 Pb Lead 82 209 Bi Bismuth 83 (210) Po Polonium 84 (210) At Astatine 85 (222) Rn Radon 86 (223) Fr Francium 87 (226) Ra Radium 88 (227) Ac Actinium 89 THE PERIODIC TABLE 1 2 Group 3 4 5 6 7 0 1 2 3 4 5 6 7 1.01 H Hydrogen 1 4.00 He Helium 2 d block s block Period p block 140 Ce Cerium 58 141 Pr Praseodymium 59 144 Nd Neodymium 60 (147) Pm Promethium 61 150 Sm Samarium 62 (153) Eu Europium 63 157 Gd Gadolinium 64 159 Tb Terbium 65 163 Dy Dysprosium 66 165 Ho Holmium 67 167 Er Erbium 68 169 Tm Thulium 69 173 Yb Ytterbium 70 175 Lu Lutetium 71 232 Th Thorium 90 (231) Pa Protactinium 91 238 U Uranium 92 (237) Np Neptunium 93 (242) Pu Plutonium 94 (243) Am Americium 95 (247) Cm Curium 96 (245) Bk Berkelium 97 (251) Cf Californium 98 (254) Es Einsteinium 99 (253) Fm Fermium 100 (256) Md Mendelevium 101 (254) No Nobelium 102 (257) Lr Lawrencium 103 f block Actinoid elements Ar Symbol Name Z relative atomic mass atomic number Key Lanthanoid elements ▴ ▴▴ ▴ ▴▴