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 moment 15 minutes Candidates answer on the Question Paper. No excess Materials are required. READ THESE INSTRUCTIONS FIRST economise your Centre twist, campaigner number and name on all the work you hand in. Write in dark blue or black pen. You may utilization a soft pencil for any diagrams, graphical records or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all movements. You are advised to show all working in calculations.Use of Data leaflet is unnecessary. At the end 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 examiners Use 1 2 Total This document consists of 9 printed pages and 3 blank pages. SPA (NF/CGW) T30933/8 UCLES 2007 Turn everyplace om .c s er UNIVERSITY OF CA MBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of nurture Advanced Subsidiary Level and Advanced Level 2 1 The hydroxides of sepa straddle I metals (LiOH, NaOH, KOH, RbOH, CsOH) are highly corrosive white solids which speedily absorb water vapour on exposure to the atmosphere.All of these solids dissolve exothermically in water. The enthalpy swap of solution, ? Hsoln, is the energy change associated with the following reaction. M represents the class 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 scud and/or ions have a smaller radius. When comparing theme I hydroxides, changes in ?Hhydration are more signifi understructuret than changes in lattice energy. (a) By considering trends in the size and charge 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 handbilld For Examiners Use experimentally in the laboratory. In experiments to compare ? Hsoln for LiOH, NaOH, KOH, RbOH, CsOH state the independent multivariate , 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 randomness given on page 2 and the apparatus you plan to use, signalize two possible starting times of error in the experiment and state how you would inform the effect of each. rror 1 .. error 2 .. 3 d) Identify a wellness and safety risk in the experiment and explain how you would minimise it when carrying pop out the experiment. 2 UCLES 200 7 9701/05/O/N/07 Turn over 4 (e) Describe the cognitive process you would carry out to find the enthalpy change of solution, ? Hsoln, for one and only(a) of the Group I hydroxides. Your plan should give a step-by-step description of the method, including how you would measure the independent variable, how you would measure the dependent variable, appropriate pilees 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 direct the enthalpy change of solution, ? Hsoln, for the reaction. 1 Total 16 UC LES 2007 9701/05/O/N/07 Turn over 6 2Students were asked to investigate how the rate of reaction between magnesium screw thread and hydrochloric acid varied with change in compactness 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 flatulency = kHCl 2 This scholarly person use the following apparatus to investigate the rate of production of hydrogen gas, H2. gas syringe magnesium ribbon disregard hydrochloric acid The student apply a 500 cm3 measuring cylinder to measure ampere-second cm3 of dilute acid into a conical flask. A 1 cm duration (0. 1 g) of magnesium ribbon was dropped into the acid in the flask and the chaw 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 knock back below. time / 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 profligate 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 was 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