10 (2410U20-1) 10 © WJEC CBAC Ltd. 10. (a) Halogenoalkanes can be hydrolysed using water in a similar way to using aqueous sodium hydroxide. A student carried out an experiment to investigate the rate of reaction for the hydrolysis of halogenoalkanes using water. The student used aqueous ethanol to dissolve the halogenoalkane and then added a few drops of aqueous silver nitrate. He timed how long it took to produce a precipitate. He obtained the results shown in the table. Halogenoalkane Time / s 1-chloropropane, C3H7Cl 300 1-bromopropane, C3H7Br 90 1-iodopropane, C3H7I 15 Bond Bond enthalpy / kJ mol–1 C—H 413 C—C 348 C—F 485 C—Cl 328 C—Br 276 C—I 240 Element Electronegativity chlorine 3.16 bromine 2.96 iodine 2.66 carbon 2.55 The student tried to explain these results and he looked on the internet to find the following data. 11 (2410U20-1) 11 Examiner only (i) Use both sets of data to explain the student’s results. Include an equation to show the hydrolysis reaction between a halogenoalkane and aqueous sodium hydroxide and name this type of reaction mechanism. [6 QER] (ii) Write an ionic equation, including state symbols, for a reaction that produces a silver halide precipitate. [1] (iii) Suggest a practical method by which the student could have obtained these results. [2] (iv) Suggest the difference that the student would have observed in his experiments if he had not added ethanol to the water before adding the halogenoalkane. [1] © WJEC CBAC Ltd. Turn over. 2410 U201 11 (2410U20-1) 12 12 Examiner only © WJEC CBAC Ltd. 16 (b) Chlorofluorocarbons, CFCs, were historically used for a variety of commercial and domestic purposes but nowadays their use is very restricted. (i) Outline the adverse environmental effects of the use of CFCs. You do not need to include any equations for the reactions involved. [4] (ii) Use relevant data in part (a) to explain why hydrofluorocarbons, HFCs, have replaced CFCs in many of their uses. [2] 13 (2410U20-1) 13 © WJEC CBAC Ltd. Turn over. BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE