2017 RVHS H2 Chemistry P4 Soln

River Valley High School Pg 1 of 12 Year 6 H2 Chemistry 9729 Practical Examination 2017 RIVER VALLEY HIGH SCHOOL YEAR 6 PRACTICAL EXAMINATION H2 CHEMISTRY 9729 23RD AUG 2017 2.5 HOURS NAME CLASS 6 ( ) INDEX NO. INSTRUCTIONS TO CANDIDATES DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Read these notes carefully. Write your name, class and index number in the spaces at the top of this page. Give details of the practical shift and la boratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graph. Do not use staples, paper clips, highlighters, 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 Note s are printed on pages 14 and 15. _________________________________________________________________________________ Answer all the questions in the spaces provided. Shift Laboratory For Examiner’s Use 1 2 Total For Examiner’s Use 1 / 21 2 / 15 3 / 09 4 / 10 Total / 55

River Valley High School Pg 2 of 12 Year 6 H2 Chemistry 9729 Practical Examination 2017 1 Determine the the percentage by mass of sodium ethanedioate in a mixture of sodium ethanedioate and ethanedioic acid. This experiment involves two steps. In step one, you will carry out a titration to find the amount of acid, H2C2O4, present in FB 3. In step two, you will carry out a second titration to find the total amount of ethanedioate ion, C2O42–, present in FB 3. Finally, you will use the values found in the two steps to calculate the percentage by mass of sodium ethanedioate in FB 3. FB 1 is 0.100 mol dm–3 sodium hydroxide, NaOH. FB 2 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4. FB 3 is a mixture of aqueous sodium ethanedioate, Na2C2O4, and ethanedioic acid, H2C2O4. FB 4 is approximately 2 mol dm–3 sulfuric acid. thymolthalein indicator Read through the whole method before starting any practical work. (a) Method Step 1 1. Fill the burette labelled FB 1 with FB 1. 2. Pipette 25.0 cm 3 of FB 3 into a conical flask. 3. Add 1 dropper full of thymolphthalein. 4. Titrate FB 3 in the conical flask with FB 1 until a pale blue colour is seen. 5. Carry out as many accurate titrations as you think necessary to obtain consistent results. 6. Record in a suitable form below all of your burette readings and the volume of FB 1 added in each accurate titration. Step 2 1. Pipette 25.0 cm 3 of FB 3 into a conical flask. 2. Using a measuring cylinder, add about 25 cm 3 of 2 mol dm–3 sulfuric acid, FB 4, to the flask. 3. Place the conical flask on a hotplate and heat to about 65°C. 4. Fill the burette labelled FB 2 with FB 2. 5. Use an appropriate method to