A Levels

w w ap eP m e tr .X w *6364028069* 9701/05 CHEMISTRY Paper 5 Planning, analysis and evaluation October/November 2007 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are undeniable. READ THESE INSTRUCTIONS FIRST Write your center of attention number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may theatrical role a soft pencil for all diagrams, represents or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO non WRITE IN ANY BARCODES. Answer all questions. You are advised to show all working in calculations.Use of Data Booklet is unnecessary. At the end up of the examination, fasten all your work securely together. The number of marks is given in brackets at the end of each question or part question. For testers Use 1 2 Total This document consists of 9 printed pages and 3 blank pages. SPA (NF/CGW) T30933/8 UCLES 2007 Turn over om .c s er UNIVERSITY OF CAMBRIDGE worldwide EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level 2 1 The hydroxides of Group I metals (LiOH, NaOH, KOH, RbOH, CsOH) are highly destructive white solids which rapidly absorb pissing vapour on exposure to the atmosphere.All of these solids dissolve exothermically in water. The enthalpy change of solution, ? Hsoln, is the energy change associated with the following reaction. M represents the Group I metal. M +(aq) + OH(aq) M OH(s) + (aq) The following diagram represents theoretical stages in the formation of aqueous MOH. M +(g) + OH-(g) + (aq) lattice energy hydration enthalpy of the ions H hydration M OH(s) + (aq) H soln M +(aq) + OH-(aq) Lattice energy and hydration enthalpy are both more exothermic when ions carry a higher charge and/or ions have a smaller radius. When comparing Group I hydroxides, changes in ?Hhydration are more significant than changes in lattice energy. (a) By considering trends in the coat and cha rge of the ions, predict the likely trend in ? Hsoln from LiOH to CsOH and sketch your prediction. Hsoln LiOH NaOH KOH RbOH CsOH 2 UCLES 2007 9701/05/O/N/07 For Examiners Use 3 (b) The enthalpy change of solution, ? Hsoln, for any Group I hydroxide can be measured For Examiners Use data-basedly in the laboratory. In experiments to compare ? Hsoln for LiOH, NaOH, KOH, RbOH, CsOH conjure up the case-by-case variable , the dependent variable . the other variable to be controlled . . . 3 (c) Draw a labelled diagram to show the apparatus you would use to obtain data from which ? Hsoln could be determined. From the information given on page 2 and the apparatus you plan to use, identify two possible sources of error in the experiment and state how you would minimise the effect of each. rror 1 .. error 2 .. 3 d) Identify a health and safety risk in the experiment and explain how you would minimise it when carrying go forth the experiment. 2 UCLES 2007 9701/05/O/N/07 Turn over 4 (e) Describe the surgical process you would carry out to find the enthalpy change of solution, ? Hsoln, for one of the Group I hydroxides. Your plan should give a step-by-step description of the manner, including how you would measure the independent variable, how you would measure the dependent variable, appropriate masses and volumes of reagents. The following data may be of use in planning the detail of your experiment. Ar Li, 6. 9 Na, 23. 0 K, 39. 1 Rb, 85. 5 Cs, 133. 0, O, 16. 0 H, 1. 0 4. 3 J are required to raise the temperature of 1. cm3 of any solution by 1C. .. .. . . .. .. 4 UCLES 2007 9701/05/O/N/07 For Examiners Use For Examiners Use 5 (f) The procedure is repeated for each of the Group I hydroxides. Show how you would tabulate the results for all the experiments. 1 (g) Show how you would use the results of one experiment to calculate the enthalpy change of solution, ? Hsoln, for the reaction. 1 Total 16 UCLES 2007 9701/05/O/N/07 Turn over 6 2 s choolchilds were asked to investigate how the rate of reaction between magnesium ribbon and hydrochloric unpleasant varied with change in concentration of the acid. 2HCl(aq) + Mg(s) MgCl2(aq) + H2(g) Student 1, looking at the equation, suggested the following. rate of production of hydrogen drift = kHCl 2 This student used the following apparatus to investigate the rate of production of hydrogen gas, H2. gas syringe magnesium ribbon dilute hydrochloric acid The student used a 500 cm3 measuring cylinder to measure nose candy cm3 of dilute acid into a conical flask. A 1 cm length (0. 1 g) of magnesium ribbon was dropped into the acid in the flask and the stopper quickly replaced in the flask. The stop-clock was started and the volume of gas collected was measured at 0. 5 minute intervals. The results of the experiment were recorded as shown in the table below. era / min time / min volume of H2 / cm3 0. 5 15. 5 5. 5 80. 0 1. 0 25. 0 6. 0 82. 5 1. 5 34. 0 6. 5 85. 0 2. 0 43. 0 7. 0 87. 0 2. 5 51. 0 7. 5 87. 5 3. 0 59. 0 8. 0 91. 0 3. 5 65. 0 8. 5 92. 5 4. 0 69. 5 9. 0 93. 5 4. 5 74. 0 9. 5 94. 5 5. 0 UCLES 2007 volume of H2 / cm3 75. 0 10. 0 95. 0 9701/05/O/N/07 ForExaminers Use For Examiners Use 7 (a) Plot a graph of volume of hydrogen produced against time. 2 (b) Identify clearly on your graph any anomalous readings and suggest a reason for these anomalous readings. 1 (c) On the graph you have plotted, construct a line from which you can calculate the initial rate of reaction.Calculate the initial rate of reaction and show your working. initial rate = .. cm3 min1 2 UCLES 2007 9701/05/O/N/07 Turn over 8 (d) By considering the experimental method described, explain why the plotted line does not pass through 0,0. 1 (e) Identify a further source of error in the method described and suggest a change to the method to reduce this error. 1 (f) Students 2-8 carried out similar experiments with different concentrations of acid. The initial rate of reaction wa s calculated for each of their experiments and is shown in the table below. Enter in the table the initial rate you have calculated for Student 1. student volume of acid used / cm3 volume of water used / cm3 mass of magnesium used /g initial rate relative concentration of acid / cm3 min1 1 100 0 0. 01 2 45 55 0. 01 8. 0 3 90 10 0. 01 16. 4 4 60 40 0. 01 11. 5 5 100 100 0. 01 9. 3 6 35 65 0. 01 6. 8 7 80