VJC Prelim P4_QP and Ans

© VJC 2018 9729/Prelim/18 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/04 Practical 30 August 2018 2 hours 30 minutes Additional Materials: As listed in the instructions below READ THESE INSTRUCTIONS FIRST Write your name and CT group 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 or 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 14 and 15. Periodic Table is printed on page 16. 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. Shift Laboratory For Examiner’s Use 1 2 3 4 Total This document consists of 16 printed pages.

2 © VJC 2018 9729/04/Prelim/18 1 You are to determine the concentration, in g dm −3, of sodium ethanedioate in a mixture of sodium ethanedioate and ethanedioic acid. This experiment involves two titrations. In titration one, you will carry out a titration to find the total amount of ethanedioate ion, C 2O42−. In titration two, you will use the information provided to find the amount of ethanedioic acid, H 2C2O4. Finally, you will use the values found in the two titrations to calculate the concentration, in g dm −3, of sodium ethanedioate in FA 1. FA 1 is a mixture of aqueous sodium ethanedioate, Na 2C2O4, and ethanedioic acid, H2C2O4. FA 2 is approximately 2 mol dm−3 sulfuric acid, H2SO4. FA 3 is 0.0200 mol dm−3 potassium manganate(VII), KMnO4. Titration One (a) 1. By using a burette, measure between 42.50 cm 3 of FA 1 into the 250 cm 3 graduated (volumetric) flask. 2. Record your burette readings and the volume of FA 1 added to the flask in the space below. Final burette reading / cm3 42.50 Initial burette reading / cm3 0.00 Volume of FA 1 used / cm3 42.50 [1] 3. Make up the contents of the flask to the 250 cm 3 mark with deionised water. Place the stopper in the flask and mix the contents thoroughly by slowly inverting the flask a number of times. Label this solution FA 4. 4. Fill a second burette with FA 3. 5. Pipette 25.0 cm 3 of FA 4 from the graduated flask into a conical