2019 JPJC Prelim H2 Chem P4 QP

 Jurong Pioneer Junior College [Turn Over NAME CLASS 18S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2019 CHEMISTRY 9729/04 Higher 2 Paper 4 Practical 26 August 2019 2 hours 30 minutes Candidates answer on the Question paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number on all the work you hand in. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a HB pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Qualitative Analysis Notes are printed on pages 23 and 24. Shift At the end of the examination, fasten all your work securely together. Laboratory The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 3 4 Total This document consists of 23 printed pages and 1 blank page.

2  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 Answer all the questions in the spaces provided. 1 Determination of the identity of the halogen, X, in CH2XCO2H For Examiner’s Use Compound W is a halogenoethanoic acid, CH2XCO2H, where X is a halogen. A halogenoethanoic acid reacts with aqueous sodium hydroxide in two reactions. The alkali neutralises the carboxylic acid. reaction 1 NaOH + CH2XCO2H  CH2XCO2Na + H2O The halogenoalkyl group then undergoes a substitution reaction. reaction 2 NaOH + CH2XCO2Na  CH2(OH)CO2Na + NaX 4 g of W were heated for one minute with 250 cm3 of 0.4 0 mol dm 3 aqueous sodium hydroxide in a beaker. Some of the sodium hydroxide reacted with compound W as shown by equations 1 and 2. The solution that remained contains unreacted sodium hydroxide. This solution is FA 1. In 1(a), you will perform a dilution and by titrating FA 1 with the diluted sulfuric acid, y ou will determine the identity of X in CH2XCO2H. FA 1 is aqueous sodium hydroxide after reaction with W. FA 2 is 2.00 mol dm3 sulfuric acid, H2SO4. methyl orange indicator (a) (i) Dilution of FA 2 1. Use a pipette to transfer 10.0 cm3 of FA 2 into a 250 cm3 volumetric flask. 2. Make up the contents of the flask to the 250 cm 3 mark with deionised water. 3. Place the stopper in the flask and mix the contents thoroughly by slowly inverting the flask a number of times. 4. Label this diluted solution of sulfuric acid as FA 3. (ii) Titration of FA 1 against FA 3 1. Fill the burette labelled FA 3, with FA 3. 2. Use a pipette to transfer 25.0 cm3 of FA 1 into the conical flask. 3. Add a few drops of methyl orange indicator. 4. Run FA 3 from the burette into the conica l flask. The end-point is reached when the yellow solution becomes orange. 5. Record your titration results , to an appropriate level of precision, in the space provided on Page 3. 6. Repeat points 2 to 5 as necessary until consistent results are obtained.

3  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 [Turn Over Titration results For Examiner’s Use [3] (iii) From your titrations, obtain a suitable volume of FA 3, VFA3, to be used in your calculations. Show clearly how you obtained this volume. VFA3 = ................................ [3] (b) (i) Calculate the concentration of sulfuric acid in FA 3 that you have prepared. [H2SO4] in FA 3 = ................................ [1] (ii) Calculate the amount of sodium hydroxide present in 25.0 cm3 of FA 1. amount of NaOH in 25.0 cm3 of FA 1 = ................................ [1]

4  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 (iii) Calculate the amount of sodium hydroxide in 250 cm3 of FA 1 and hence, calculate the amount of sodium hydroxide that reacted with W. For Examiner’s Use amount of NaOH that reacted with W = ................................ [2] (iv) Use your answer to (b)(iii) to calculate the Mr of W, CH2XCO2H. Hence, deduce the identity of X in CH2XCO2H. [Ar: C,12.0; O,16.0; H, 1.0; F, 19.0; Cl, 35.5; Br, 79.9; I, 126.9] X is ................................ [2] (c) (i) The maximum error in any single burette reading is ±0.05 cm3. Calculate the maximum percentage error in the volume of FA 3 used in 1(a)(iii). maximum percentage error in the volume of FA 3 used = ........................... [1]

5  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 [Turn Over (ii) Apart from the inaccuracies in reading the volumes of solutions, suggest a significant source of error in this experiment. Explain how you could minimise this error. For Examiner’s Use ...................................................................................................................... ...................................................................................................................... [1] [Total: 14]

6  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 2 An experiment to investigate the behaviour of acids and bases in aqueous solutions For Examiner’s Use FA 4 is 1.00 mol dm3 sodium hydrogencarbonate, NaHCO3. FA 5 is aqueous sodium hydroxide. You will need access to the FA 2 solution you used earlier. According to Arrhenius theory of acids and bases, an acid produces H + ions and a base produces OH ions, in aqueous solution. An acidbase reaction involves reacting together these two ions to produce water molecules as shown in the following equation. H+(aq) + OH(aq)  H2O(l) Hneutralisation = 57.0 kJ mol1 This experiment involves two different acid-base reactions. The first reaction is between sodium hydrogencarbonate, FA 4 , and sodium hydroxide, FA 5. reaction 3 NaHCO3(aq) + NaOH(aq)  Na2CO3(aq) + H2O(l) H3 The molar enthalpy change for reaction 3, H3, is the enthalpy change when 1.0 0 mol of NaHCO3 reacts completely with NaOH. Instead of using an indicator to determine the end point, you will perform a thermometric titration to determine the equivalence point of the reaction. You will add portions of FA 5 progressively to a known volu me of FA 4 . You will continue adding FA 5 until the equivalence point is reached and passed. Throughout the experiment you will note and record the temperature of the mixture after each addition. You will then analyse your results graphically to determine the  titration volume at the equivalence point, Vequivalence,  maximum temperature change, Tmax,  molar enthalpy change, H3, for reaction 3.

7  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2019 [Turn Over (a) Determination of the enthalpy change of reaction between FA 4 and FA 5 For Examiner’s Use In this experiment you will need to record the maximum temperature of the reaction mixture when specified volumes of FA 5 have been added. It is important that the volume of FA 5 recorded is the total volume you have added up to that point when the temperature reading was made. Note: If you overshoot on an addition, record the actual total volume of FA 5 added up to that point. In an appropriate format in the space provided below, record all values of temperature, T, and each total volume of FA 5 added. 1. Fill a burette with FA 5. 2. Place a Styr