RVHS H2 Chem 2013 Prelim P2 QP

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 6 CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9647/02 Paper 2 Structured Questions 24 September 2013 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class, Centre number and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. 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 in the space provided. A Data Booklet is provided. Do NOT write anything on it. 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. ____________________________________________________________________________ This document consists of 19 printed pages and 1 blank page. For Examiner’s Use Paper 2 Question Number 1 2 3 4 5 6 Total Marks 12 14 4 11 16 15 72 Paper 1 40 Paper 3 80 Total 192 1069

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 2 1 Planning (P) Rust is mainly made up of iron ( III) oxide. An old rusty iron box can be restored by submerging the box in acid solution to remove the rust, followed by coating the iron box with a layer of metals such as chromium, aluminium or zinc using electrolysis. A student tries to adapt this process to restore a rusty iron box using only materials that are available in the school laboratory. She removed the rust on the box by submerging it in 1 mol dm 3 sulfuric acid. Then she coats the rust free box with a layer of copper using electrolysis. The diagram below shows part of the experimental set up. (a) Write a balanced equation, including state symbols, for the reaction that removes rust from the box using sulfuric acid. [1] (b) Other than safety issues, what is the disadvantage of using strong acid to remove rust from the box? [1] 1 A A 11 variable resistor +  1070

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 3 (c) Complete and label the diagram abov e to show the experimental set- up for coating the rust free box with copper metal by electrolysis. Give the composition of a suitable electrolyte. [2] (d) Write the equation for the reaction at the anode and cathode. Cathode: Anode: [1] (e) The variable resistor can be used to vary the current that is passed through a closed circuit. Predict how does the amount of copper deposited in a fixed duration (t) varies as current is increased from 0.00A until 1.00A. Display your prediction in the form of a sketch graph. [1] 1071

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 4 (f) Design a laboratory experiment to investigate your prediction in (e) and hence allow an experimental value for Faraday’s Constant to be obtained. The following apparatus and chemicals are available for used. Wires Switch Digital Ammeter ( 0.001A) Variable resistor Batteries Mass balance ( 0.001g) Pure copper strips Copper (II) sulfate solution (i) The percentage error for the mass weighed using the mass balance should not exceed 1%. Ca lculate the minimum duration of time, in minutes, for 0.400 A of current to be passed through the circuit. 1072

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 5 (ii) Considering your answer in (f)(i), write a detaile d plan for your experiment. Your plan should contain the following  all essential experimental details  the precautions taken to ensure accuracy  outline of how the results w ould be used to verify your predicted graph in (e).  hence explain how the results can be used to determine a value for the Faraday constant. 1073

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 6 [6] [Total: 12] 1074

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 7 BLANK PAGE 1075

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 8 2 Haze levels in Singapore hit a record high of PSI 401 on 21 June this year, as a consequence of widespread forest fires in Indonesia. Many hospitals and clinics reported a spik e in the number of pat ients seeking medical attention for respiratory problems, such as asthma and rhinitis. To provide quick relief from asthma symptoms, the dr ug salbutamol is commonly prescribed. salbutamol (a) Identify two functional groups, other than phenyl, that are present in salbutamol. [1] (b) Salbutamol is sold in pharmacies as a racemic mixture, mainly because the ( S)-enantiomer blocks metabolism pathways while the (R)-enantiomer shows activity. Identify the type of stereoisomerism salbutamol exhibits and draw two structures to illustrate this. [2] 1076

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 9 A 4-step synthesis route of salbutamol is shown as follows: (c) An organic chemist suggested t he use of bromine gas under ultraviolet light in Step 2 . Explain why his choice of reagent and condition may not be appropriate for the conversion. [1] (d) Name the reaction in Step 3 and outline the mechanism. You may use R to denote bulky alkyl groups in your mechanism. Name of reaction: [4] Step 2 Step 3 1077

River Valley High School 9647/02/PRELIM/13 [Turn over Preliminary Examination 2013 10 (e) Explain why LiAlH4 must be used in dry ether during the final step? [1] (f) A laboratory technician realised that the labels to the bottles containing aspirin and another compound had fallen off. aspirin compound X Suggest a simple chemical test to distinguish between these two compounds. [2] 1078