Model Practice Test-2 University of London AS level Examinations Chemistry Unit 3b: synoptic test Index Number Name Advance Level Subject code: 6243.b Time: 1 hour Instruction to the candidates In the box above write your name and index number. Answer ALL the questions in the spaces provided in this question paper. Question number Leave blank Information for the candidates The total mark for this paper is 50. The marks, for individual questions and parts of questions are shown in round bracket. e.g. there are 1 pages in this question paper. All blank pages are indicated. Calculators may be used. Advice to the candidate You are reminded of the importance of clear and careful presentation in English in your answer. You are also reminded that you should take all usual safety precautions when working in a chemistry laboratory. Total Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 1
1. The pairs of compounds given in parts (a) to (d) may be distinguished by the test stated. For each compound in the pair, describe the observations you would expect to make when the test is carried out. If a gas is evolved, include the name of the gas. (a) Solid sodium chloride and solid potassium chloride. Test: Flame test. Observation with sodium chloride...... Observation with potassium chloride...... (b) Aqueous potassium sulphate and aqueous potassium sulphite. Test: Addition of dilute hydrochloric acid followed by aqueous barium chloride. Observation with potassium sulphate...... Observation with potassium sulphite...... (c) Solid ammonium sulphate and solid potassium sulphate. Test: Warm with aqueous sodium hydroxide, testing any gas with damp red litmus paper. Observation with ammonium sulphate......... Observation with potassium sulphate...... (3) Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 2
(d) Solid sodium chloride and solid sodium bromide. Test: Add concentrated sulphuric acid, testing any gas evolved with damp blue litmus paper. Observations with sodium chloride......... Observations with sodium bromide...... (5) (Total 12 marks) 2. You are provided with the following apparatus and materials. A burette ready to use filled with a solution of aqueous sodium hydroxide. An aqueous solution of 0.0500 mol dm 3 ethanedioic acid. Phenolphthalein indicator. Access to the full range of laboratory volumetric apparatus. (a) Describe how you would carry out titrations to find the volume of sodium hydroxide that reacts with 25.0 cm 3 of the aqueous ethanedioic acid. In your answer you must include how you would detect the end point and what you would do to obtain a reliable result. You do not need to include any details of calculations you may carry out on your results....... Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 3
(6) (b) The reaction involved in the titration is (COOH) 2 (aq) + 2NaOH(aq) (COONa) 2 (aq) + 2H 2 O(l) 25.0 cm 3 of the aqueous 0.0500 mol dm 3 ethanedioic acid required 25.50 cm 3 of the aqueous sodium hydroxide for neutralisation. (i) Calculate the amount (moles) of ethanedioic acid in 25.0 cm 3 of the solution. (ii) Calculate the amount (moles) of sodium hydroxide in 25.50 cm 3 of the solution. (iii) Calculate the concentration of the sodium hydroxide solution in mol dm 3. Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 4
(c) Calculate the mass of hydrated ethanedioic acid, (COOH) 2.2H 2 O, needed to make up 200 cm 3 of aqueous 0.0500 mol dm 3 solution. Give your answer to three significant figures. (3) (d) When making up the solution of ethanedioic acid a student, by mistake, uses a 200 cm 3 instead of a 250 cm 3 volumetric flask. The student dissolves the mass of ethanedioic acid crystals calculated to make up 250 cm 3. Explain what effect this would have on the student's volume of sodium hydroxide solution used in the titration. [No calculation is required in your answer.] (Total 14 marks) 3. In two similar, separate experiments the enthalpy changes for the reactions of sodium hydrogencarbonate and sodium carbonate with excess dilute hydrochloric acid were determined. (a) The first experiment was to find the enthalpy change, H 1, for the reaction NaHCO 3 (s) + HCl(aq) NaCl(aq) + CO 2 (g) + H 2 O(l) Measurement Mass of solid sodium hydrogencarbonate added to hydrochloric acid. Reading 5.00 g Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 5
Volume of hydrochloric acid 50.0 cm 3 Temperature of hydrochloric acid before addition of solid sodium hydrogencarbonate 22.0 C Final temperature of solution 15.5 C Molar mass of sodium hydrogencarbonate 84.0 g mol 1 Specific heat capacity of solution 4.18 J g 1 C 1 (i) Calculate the amount (moles) of sodium hydrogencarbonate used. (ii) Calculate the heat absorbed in the reaction in kj. [Assume that 1 cm 3 of solution has a mass of 1 g] (iii) Calculate the value of H 1 in kj mol 1. Include a sign in your answer expressing it to a number of significant figures suggested by the data in the table. Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 6
(b) In the second experiment the enthalpy change for the reaction between sodium carbonate and dilute hydrochloric acid was measured. Na 2 CO 3 (s) + 2HCl (aq) 2NaCI(aq) + CO 2 (g) + H 2 O(l) The molar enthalpy change, H 2, was calculated to be 35.6 kj mol 1 (i) Give TWO ways in which the temperature change differs when equal molar amounts of sodium hydrogencarbonate and sodium carbonate react separately with the same volume of hydrochloric acid. (ii) Give ONE assumption that has been made in calculating the values of H 1, and H 2 from experimental results. (Total 8 marks) 4. Ethanol is oxidised when it reacts with a mixture of reagent A and sulphuric acid. Using the distillation apparatus shown in the diagram, the reaction may be used to prepare an aqueous solution of ethanal. The reaction taking place is shown by the equation below, where [O] represents the oxidising agent. CH 3 CH 2 OH + [O] CH 3 CHO + H 2 O Data Ethanal CH 3 CHO volatile liquid, boiling temperature 21 C miscible with water flammable irritant, harmful vapour molar mass 44 g mol 1 Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 7
Reagent A + water + ethanol Aqueous sulphuric acid To fume cupboard Heat Ice/water (a) Give the name or formula of reagent A. (b) The preparation is carried out by heating the flask until the aqueous sulphuric acid begins to boil, removing the heat source and then adding the mixture from the separating funnel slowly. The solution in the flask continues to boil. (i) What conclusion can you make about the reaction in the flask based on the fact that the solution continues to boil after the heat source is removed? (ii) Describe how the condenser converts hot vapour into liquid. (iii) Suggest a reason for surrounding the collection flask with an ice/water mixture. (iv) Suggest a reason for the tube leading to the fume cupboard. (c) Calculate the mass of ethanal that would be formed from 5.0 g of ethanol, assuming a 40 % yield. [Molar mass of ethanol is 46 g mol 1 ] (Total 7 marks) Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 8
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Edexcel-modelpaper-unit3b-paper2 Jaydip.Chaudhuri 10 3 11 19 37 55 87 4 12 20 38 56 88 21 39 57 89 22 40 72 104 23 41 73 105 24 42 74 106 25 43 75 58 90 59 91 60 92 61 93 62 94 63 95 64 96 65 97 66 98 67 99 68 100 69 101 70 102 71 103 26 44 76 27 45 77 28 46 78 29 47 79 30 48 80 5 13 31 49 81 6 14 32 50 82 7 15 33 51 83 8 16 34 52 84 9 17 35 53 85 10 18 36 54 86 Li Na K Rb Cs Fr 7 23 39 85 133 (223) 9 24 40 88 137 (226) 45 89 139 (227) 48 91 178 (261) 51 93 181 (262) 52 96 184 (263) 55 (99) 186 140 232 141 (231) 144 238 (147) (237) 150 (242) 152 (243) 157 (247) 159 (245) 163 (251) 165 (254) 167 (253) 169 (256) 173 (254) 175 (257) 56 101 190 59 103 192 59 106 195 63.5 108 197 65.4 112 201 11 27 70 115 204 12 28 73 119 207 14 31 75 122 209 16 32 79 128 (210) 19 35.5 80 127 (210) 20 40 84 131 (222) Lithium Sodium Potassium Rubidium Caesium Francium Berylium Magnesium Calcium Strontium Barium Radium Scandium Yttrium Lanthanum Actinium Titanium Zirconium Hafnium Unnilquadium Vanadium Niobium Tantalum Unnilpentium Chromium Molybdenum Tungsten Unnilhexium Manganese Technetium Rhenium Cerium Thorium Praseodymium Protactinium Neodimium Uranium Promethium Neptunium Samarium Plutonium Europium Americium Gadolinium Curium Terbium Berkelium Dysprosium Californium Holmium Einsteinium Erbium Fermium Thulium Mendelevium Ytterbium Nobelium Lutetium Lawrencium Iron Ruthenium Osmium Cobalt Rhodium Iridium Nickel Palladium Platinum Copper Silver Gold Zinc Cadmium Mercury Boron Aluminium Gallium Indium Thallium Carbon Silicon Germanium Tin Lead Nitrogen Phosphorus Arsenic Antimony Bismuth Oxygen Sulphur Selenium Tellurium Polonium Fluorine Chlorine Bromine Iodine Astatine Neon Argon Krypton Xenon Radon Helium Hydrogen 1 2 1 4 H Be Mg Ca Sr Ba Ra Sc Y La Ac Ti Zr Hf Unq V Nb Ta Unp Cr Mo W Unh Mn Tc Re Ce Th Pr Pa Nd U Pm Np Sm Pu Eu Am Gd Cm Tb Bk Dy Cf Ho Es Er Fm Tm Md Yb No Lu Lr Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg B Al Ga In Ti C Si Ge Sn Pb N P As Sb Bi O S Se Te Po F Cl Br I At Ne Ar Kr Xe Rn He Atomic Number Symbol Name Molar mass in g mol 1 eriod Key Group THE PERIODIC TABLE 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Lanthanide elements Actinide elements