RI H2 Chem P2 Prelim

1   © Raffles Institution 9647/02/S/14 [Turn Over RAFFLES INSTITUTION 2014 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9647/02 Paper 2 Structured Questions 17 September 2014 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces provided at the top of this page. Write in dark blue or black pen in the spaces provided. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. A Data Booklet is provided. Do not write anything on it. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 12 2 / 10 3 / 12 4 / 14 5 / 24 Total / 72 This document consists of 19 printed pages.

2 © Raffles Institution 9647/02/S/14 [Turn Over 1 Planning You are to plan an experiment to investigate how the rate of the reaction between propanone and iodine, catalysed by dilute sulfuric acid, depends on temperature and to calculate the activation energy, E a, for the reaction. When excess propanone and iodine react in the presence of dilute sulfuric acid, iodine is decolourised and the brown solution becomes colourless when iodine is used up. In the reaction, one of the hydrogen atoms in propanone is replaced by an iodine atom and hydroiodic acid is produced. (a) Construct a balanced chemical equation for the reaction. …..……………………………………………………………………………..………..… [1] A teacher demonstrates this experiment as follows. She prepares two separate solutions, X and Y. Solution X contains 5.00 g dm 3 iodine solution. Solution Y is a mixture of 500 cm 3 of 1.0 mol dm 3 propanone and 500 cm 3 of 1.0 mol dm3 dilute sulfuric acid. She mixes 10 cm 3 of solution X with 10 cm 3 of solution Y at 35 oC and, after 40 seconds, the mixture decolourises. (b) Consider the description of the experiment given above. The dependence of the reaction rate on temperature may be determined by performing a number of experiments at different temperatures. You may find it useful to use 1/t to represent the reaction rate, where t is the time taken for the reaction mixture to decolourise. (i) Draw a labelled diagram of the experimental setup you would use to carry out this experiment. You should use only standard apparatus found in a school laboratory and show clearly the following:  the apparatus used as the reaction vessel  how the thermometer will be positioned in order to measure the temperature of the solution as accurately as possible  how the temperature can be controlled For Examiner’s Use

3 © Raffles Institution 9647/02/S/14 [Turn Over (ii) Write a plan for such a series of experiments. In your plan, you should use the same volumes of solution X and solution Y described on page 2. Your plan should ensure that at least one of your experiments would be expected to take more than 40 seconds. You may assume that you are provided with the following:  solution X containing 5.00 g of iodine in 1.0 dm3 of water  1.0 mol dm 3 dilute sulfuric acid  5.0 mol dm 3 propanone solution  deionised water  the apparatus normally found in a school laboratory Your plan should contain the following:  details for the preparation of 1.0 mol dm 3 propanone solution from the propanone solution provided  details for the preparation of solution Y  the number of experiments you would carry out  the range of temperatures at which the experiments would be carried out  what temperature measurements you would make  all essential experimental details ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… …..……………………………………………………………………………..………..… For Examiner’s Use

4 © Raffles Institution 9647/02/S/14 [Turn Over ……………………………………………………………………………..……..……..… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..………..……. ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… ……………………………………………………………………………..……………… …..……………………………………………………………………………..………..… [8] For Examiner’s Use

5 © Raffles Institution 9647/02/S/14 [Turn Over (c) Identify one potential safety hazard in this experiment and state how you would minimise this risk. [1] (d) The Arrhenius equation is k = a RTAe E , where k is the rate constant, A is the Arrhenius constant, Ea is the activation energy, R is the molar gas constant, and T is the thermodynamic temperature in Kelvins. The Arrhenius equation may also be expressed in the following linear form: ln k = ln A  a RT E (i) State the relationship between k and t, the time taken for the reaction mixture to decolourise. (ii) In the axes below, draw a suitable straight-line graph using only the data collected in your experiment and show how Ea can be found. Label the axes of your graph clearly. [2] [Total: 12] For Examiner’s Use

6 © Raffles Institution 9647/02/S/14 [Turn Over 2 Halogens form many interhalogen compounds and ions, in which a halogen atom lower down in the group is surrounded by atoms of halogens higher in the group. Iodine forms three diatomic interhalogen compounds: IF, ICl and IBr. Species Bond energy / kJ mol–1 I–F 277 I–Cl 208 I–Br 175 (a) On heating, iodine monobromide decomposes to give iodine and bromine. I Br(g)  ½ I2(g) + ½ Br2(g) (i) Using bond energies in the Data Booklet and in the table, calculate the enthalpy change, ∆Hr, of the above reaction. (ii) Describe and explain how the thermal stability of the diatomic interhalogen compounds formed by iodine varies down Group VII. ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..………………………… ..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…………………………