IJC H2 Chem 2012 Prelim P3 QP

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2 in preparation for General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLASS IN DEX NUMBER CHEMISTRY 9647/03 Paper 3 Free Response 14 September 2012 2 hours Candidates answer on separate paper. Additional Materials: Writing Papers Data booklet Cover Page READ THESE INSTRUCTIONS FIRST Write your name and class 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 4 out of 5 questions. Begin each answer on a fresh sheet of paper. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. At the end of the examination, fasten all your work securely together. The number of marks is given in the brackets [ ] at the end of each question or part question. This document consists of 13 printed pages and 1 blank page. Innova Junior College [Turn over

2 PRELIM 2 © INNOVA 9647/03/2012 [Turn over Answer 4 out of 5 questions. 1 (a) N,N-dimethyltryptamine is a psychoactive drug whose primary action is to alter cognition and perception. Depending on the dose and method of administration, its subjective effects can range from short-lived milder psychedelic states to powerful immersive experiences. (i) Suggest a reason why N,N-dimethyltryptamine is soluble in acidic solutions. (ii) Would you expect N,N-dimethyltryptamine to have a high or low melting point? Explain your answer in terms of structure and bonding. [4] (b) para-Methoxyamphetamine first came into circulation in the early 1970s and went by the street names of "Chicken Powder" and "Chicken Yellow" and was found to be the cause of a number of drug overdose deaths in the United States and Canada at that time. It can be synthesised by the following route. (i) Suggest reagents and conditions for steps II and III. (ii) What type of reaction is step II? (iii) Suggest why compound J is converted into K before step II is carried out. (iv) What type of stereoisomerism does para-methoxyamphetamine exhibits? Draw the structures of the stereoisomers of para-methoxyamphetamine. [6]

3 PRELIM 2 © INNOVA 9647/03/2012 [Turn over (c) Propene is an important starting product in the petrochemical industry and is often used as the raw material for a wide variety of products. (i) Name and describe the mechanism of the reaction between propene and hydrogen bromide. (ii) The bromine atom in the product from (i) is very reactive towards nucleophilic reagents. The bromine atom in 1–bromopropene is unreactive towards nucleophilic reagents. Suggest an explanation for the unreactivity of the bromine atom in 1–bromopropene. [5] (d) Compound P is a neutral, sweet-smelling liquid with molecular formula C 5H8O2. It reacts with hot sulfuric acid to give a single compound Q, C 5H10O3. Q has two stereoisomers and gives a pale yellow precipitate with alkaline iodine and compound R. Deduce the structures of P, Q and R. [5] [Total:20]

4 PRELIM 2 © INNOVA 9647/03/2012 [Turn over 2 (a) When a precipitate is formed, ∆Gθ ppt, in kJ mol -1, is given by the following expression. ∆Gθ ppt = 1000 K log 2.303RTsp (i) Given that the Ksp value of BaF 2 is 1.70 x 10 -6 at 298 K, calculate ∆Gθ ppt, in kJ mol-1, for BaF2. (ii) The standard enthalpy change of formation of BaF 2 is −858 kJ mol-1. Use your answer in (a)(i) to calculate ∆Sθ ppt, in J mol -1 K-1 for the formation of the precipitate at 298 K. (iii) Explain the significance of the sign of your answer in (ii). (iv) Predict and explain whether the precipitation will be feasible at high or low temperature. (v) Suggest how the magnitude of the lattice energy of BaF 2 might compare to that of BaCl2. Explain your answer. [7] (b) In the past, chemical analysis was carried out by chemists using traditional laboratory apparatus. Many qualitative tests used depended on an application of the principles of solubility product. (i) Write an expression for the K sp of barium fluoride. (ii) Predict whether precipitation occurs if 50.0 cm 3 of 0.150 mol dm –3 of Ba(OH) 2 solution is mixed with 50.0 cm 3 of 0.100 mol dm –3 of KF solution in the laboratory. The K sp of BaF2 is 1.70 x 10-6 mol3 dm-9. [3] (c) Myrcene is a naturally occurring compound found in the leaves of bay trees. It is known to be a polyunsaturated hydrocarbon. It can react with hydrogen to produce a saturated hydrocarbon. In a laboratory investigation, a 1.00 g sample of pure myrcene fully reacted with exactly 510 cm 3 of hydrogen gas measured at 20.0°C and 105.0 kPa. In this reaction, myrcene was converted to a saturated alkane with a molecular formula C10H22. (i) What type of reaction has occurred between the myrcene and hydrogen? (ii) Calculate the amount, in moles, of hydrogen reacting. (iii) Calculate the mass of C10H22 produced in the reaction. (iv) Determine the number of double bonds in each molecule of myrcene. [6]

5 PRELIM 2 © INNOVA 9647/03/2012 [Turn over (d) In September 2009, the wholesale of weedkiller containing chlorate(V) ions was banned in various European countries. Chlorate(V) ions can act as a strong oxidising agent in acid solution according to the following half equation: ClO 3 −(aq) +6H+(aq) + 6e  Cl−(aq) + 3H2O(l) In an experiment, 25.0 cm 3 of a sample of sodium chlorate(V) solution reacted with an excess of sodium iodide, Na I. The iodine produced required 25.00 cm 3 of 1 mol dm-3 of sodium thiosulfate, Na2S2O3, for complete reaction. (i) Write a balanced equation between chlorate(V) ions and iodide ions in acidic medium. (ii) Calculate the number of moles of iodine liberated by the chlorate(V) solution. (iii) Calculate the concentration of sodium chlorate(V) in the solution. [4] [Total: 20]

6 PRELIM 2 © INNOVA 9647/03/2012 [Turn over 3 (a) A sample of aspirin was prepared by reacting 2.20 g of salicylic acid with 4.20 cm 3 of ethanoic anhydride in a conical flask. After heating for 20 minutes the reaction mixture was cooled and white crystals precipitated. The crystals were then collected, dried to constant mass and weighed. The equation for the reaction is: The following results were obtained. mass of salicylic acid 2.20 g volume ethanoic anhydride 4.20 cm 3 mass of product 2.25 g Use the following data to answer the questions below. molar mass (g mol -1) density (g cm -3) aspirin 180 − ethanoic anhydride 102 1.08 salicyclic acid 138 − (i) Calculate the initial amount, in moles, of salicylic acid used in this preparation. (ii) What initial amount, in moles, of ethanoic anhydride was used? (iii) What is the maximum mass of aspirin that can theoretically be produced from these reagents? (iv) Determine the percentage yield in this preparation. (v) To check whether the aspirin obtained is contaminated with salicyclic acid