HCI Prelim_P3

This document consists of 11 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 14S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on separate paper. Additional Materials: Answer Paper Data Booklet 9647/03 17 September 2015 2 hours INSTRUCTIONS TO CANDIDATES Write your name and class on all the work you hand in. Write in dark blue or black pen. 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 any four questions. Begin each question on a new piece of paper. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. Circle the question numbers for the questions that you have attempted on the cover page provided.

2 © Hwa Chong Institution 2015 9647 / 03 / C2 Prelim 2015 Answer any four questions. 1 Margarine was first created in 1869 as a response to a challenge from the French emperor Louis Napoleon III to make a cheap substitute for butter for the army and lower classes. Today, margarine is made by passing hydrogen gas over unsaturated vegetable oils in the presence of a nickel catalyst. A representative reaction may be written as given below: (a) (i) State the type of catalysis that this hydrogenation reaction undergoes. [1] (ii) State the type of isomerism that the product displays and draw diagrams to illustrate the isomerism. [2] (iii) In this type of catalysis, one side (bottom face) of the planar alkene molecule is adsorbed to the surface of the catalyst. Both the hydrogen atoms will be added to the same side of the alkene which is adsorbed to the catalyst and not the other side (top face). The diagram below illustrates how the alkene molecule may be adsorbed to the surface of the catalyst. In the light of this information and your answer to (a)(ii), explain why the product mixture does not rotate plane-polarised light. The use of a diagram may aid in the clarity of your explanation. [3] (b) (i) Using appropriate data from the Data Booklet, calculate the standard enthalpy change of reaction for the reaction given above. [2] (ii) Based on your answer for (b)(i), under what conditions would you expect the hydrogenation reaction to be spontaneous? [2] (iii) Hence explain why a catalyst is still required for the hydrogenation. [2]

3 © Hwa Chong Institution 2015 9647 / 03 / C2 Prelim 2015 (c) A much more effective rhodium-based c