10 (2410U10-1) Examiner only 10. (a) Group 1 and Group 2 metals are in the s-block of the Periodic Table. Using potassium and calcium as examples, discuss the similarities and differences between Group 1 and Group 2 with respect to: • the reaction of the metals with cold water. • the solubility of the carbonates. [6 QER] You should include appropriate chemical equations in your answer. © WJEC CBAC Ltd. 10 (2410U10-1) Turn over. 11 Examiner only (b) The equation for the reaction between potassium carbonate and hydrochloric acid is given below. K2CO3 2KCl 2HCl + H2O + CO2 + A 1.40 g sample of impure potassium carbonate was added to excess dilute hydrochloric acid. The impurity is unreactive and only the potassium carbonate reacts with the acid. The volume of carbon dioxide released was 186 cm3 when measured at 298 K and 1.01 × 105 Pa. Calculate the mass of the impurity. [3] mass of impurity = ........................................................ g (c) A solution is thought to contain potassium chloride. Describe suitable tests that a student could do to confirm this. Include the expected observations. [2] (d) By referring to ionisation energies, explain why stable compounds containing K2+ ions are unlikely to form. [2] © WJEC CBAC Ltd. 11 13 12 (2410U10-1) Examiner only 11. (a) Arsenic oxide, As2O3, is prepared on an industrial scale by roasting arsenic-containing ores such as arsenopyrite, FeAsS, in air. The other products formed are iron(III) oxide and sulfur dioxide. (i) State the oxidation state of arsenic in As2O3. [1] (ii) Give a balanced chemical equation for the industrial production of As2O3 from FeAsS. [2] (b) As2O3 is moderately soluble in water. 100 cm3 of a saturated solution at 25 °C contains 2.06 g. When dissolved in water, the oxide reacts to form arsenous acid. As2O3 2H3AsO3 3H2O + (i) Calculate the concentration of the arsenous acid, in mol dm–3, in the saturated solution. [3] concentration of H3AsO3 = ........................................................ mol dm–3 (ii) A solution of arsenous acid has a pH of 5.11. Calculate the hydrogen ion concentration of this solution. [1] [H+] = ........................................................ mol dm–3 © WJEC CBAC Ltd. 12 (2410U10-1) Turn over. 13 Examiner only (c) The formula for arsenous acid can be written as As(OH)3 since it contains three hydroxyl (OH) groups bonded to arsenic. Suggest the shape around the arsenic atom in As(OH)3. Justify your answer by using VSEPR theory. [3] (d) Phosphorus can form two chlorides, PCl3 and PCl5. 0.181 g of a chloride of phosphorus gave 39 cm3 of vapour at 1 atm pressure when heated to 87 °C. The sample was completely vapourised. Show that the chloride of phosphorus was PCl3. [4] © WJEC CBAC Ltd. 13 14 (2410U10-1) © WJEC CBAC Ltd. 14 Examiner only (e) The molecular ion region of the mass spectrum of PCl3, is shown below. 0 20 40 60 80 100 10 30 50 70 90 60 70 80 90 100 110 120 130 140 Relative abundance Mass / charge ratio (m/z) C D E (i) Identify the species responsible for peak C at m/z 101. [1] (ii) Explain why the height ratio of peaks C:E is 9:1. [2] 17 (2410U10-1) Turn over. 15 © WJEC CBAC Ltd. 15 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE 16 (2410U10-1) © WJEC CBAC Ltd. 16 Examiner only 12. A student was asked to find the identity of a Group 1 metal carbonate by titration. He was told to use the following method. • Weigh a sample of the carbonate in a weighing bottle. • Transfer the carbonate into a beaker and weigh the bottle afterwards. • Add water to the beaker to dissolve the carbonate. • Transfer the solution to a volumetric flask. • Add more water to make the final volume 250.0 cm3 of solution. • Accurately transfer 25.0 cm3 of this solution into a conical flask. • Add 2–3 drops of a suitable indicator to this solution. • Fill a burette with 0.100 mol dm–3 hydrochloric acid solution. • Carry out a rough titration of the carbonate solution with the hydrochloric acid. • Accurately repeat the titration until you get concordant titres and calculate a mean titre. (a) Another student said that there were two errors in making the 250.0 cm3 carbonate solution. Error 1: A small amount of solid remained in the weighing bottle. Error 2: A small amount of solution remained in the beaker. Comment on the suggested errors. If the student is correct suggest how the method could be improved. If the student is incorrect, explain why. [2] Error 1 Error 2 (b) State why he adds an indicator to this solution. [1] (c) Suggest why he was told to carry out a rough titration first. [1] (2410U10-1) Turn over. 17 © WJEC CBAC Ltd. 17 Examiner only (d) State what you understand by the term ‘concordant titres’. [1] (e) Some of the student’s results are shown below: Mass of weighing bottle + carbonate / g 13.73 Mass of weighing bottle / g 12.48 Titration Rough 1 2 3 Final reading / cm3 24.20 23.70 .............................. .............................. Initial reading / cm3 0.00 0.10 .............................. .............................. Titre / cm3 .............................. .............................. .............................. .............................. concentration of hydrochloric acid = 0.100 mol dm–3 The diagrams below show the initial burette reading and the final burette reading for the second and third titrations. 1 0 Titration 2 Initial reading Final reading Titration 3 Initial reading Final reading 1 0 24 23 24 23 Complete the student’s table and calculate the mean titre. [3] mean titre = ........................................................ cm3 Examiner only 18 (2410U10-1) © WJEC CBAC Ltd. 18 (f) The equation for the reaction between the metal carbonate and hydrochloric acid is given below. M represents the symbol of the Group 1 metal. M2CO3 2MCl 2HCl + H2O + CO2 + (i) Calculate the number of moles of M2CO3 in 25.0 cm3 of the solution. [2] number of moles = ........................................................ (ii) Calculate the relative formula mass of the carbonate and hence deduce the Group 1 metal in the carbonate. You must show your working. [4] group 1 metal = ........................................................ END OF PAPER 14 (2410U10-1) Turn over. 19 © WJEC CBAC Ltd. 19 Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only 20 (2410U10-1) © WJEC CBAC Ltd. 20 Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only BE*(S22-2410U10-1A) © WJEC CBAC Ltd. GCE AS/A LEVEL 2410U10-1A TUESDAY, 17 MAY 2022 – MORNING CHEMISTRY – AS unit 1 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 Z22-2410U10-1A 2 © WJEC CBAC Ltd. (2410U10-1A) 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. 3 © WJEC CBAC Ltd. (2410U10-1A) *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 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 ▴ ▴▴ ▴ ▴▴ © WJEC CBAC Ltd. 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