2018 C1 Promotional Exam Paper 3

This document consists of 7 printed pages. HWA CHONG INSTITUTION C1 Promotional Examination Higher 2 NAME CT GROUP 18S CHEMISTRY Paper 3 Free Response Candidates answer on separate paper. Additional Materials: Answer Paper, Graph Paper, Cover Page and Data Booklet. 9729/03 2 October 2018 1 hour READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Question 1 is a compulsory question. Section B Answer only one question from this section. Begin each question on a new piece of paper. The use of an approved scientific calculator is expected, where appropriate. 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, together with the cover page.

2 2018 HCI C1 H2 Chemistry Promotional Exam / Paper 3 Section A Question 1 is a compulsory question. All candidates should answer this question. 1 (a) The Haber process is the main industrial procedure for the production of ammonia from nitrogen and hydrogen. N2(g) + 3H2(g) = 2NH3(g) (i) State Le Chatelier’s Principle. [1] (ii) The optimal operating temperature for the Haber process is 450 oC. Use the following values to calculate the DGro at 450 oC. DHro= – 92.0 kJ mol–1 DSro = – 199 J K–1 mol–1 [1] (iii) Calculate the value of the equilibrium constant for the Haber process at the same temperature using DGro = – RTlnK. Explain the significance of your answer in terms of the yield of the process. [2] (iv) State the usual operating pressure (in atm) required for the Haber process and explain why it is necessary for an acceptable yield in the industrial procedure. [2] (b) Disinfecting solutions often contain hypochlorous acid, HOCl, which can react with alkenes via electrophilic addition. When hypochlorous acid reacts with but-1-ene, the major product obtained is 1-chlorobutan-2-ol. (i) Deduce which atom in the HOCl molecule is the electrophilic site responsible for the product shown. [1] (ii) Describe the mechanism of the reaction between HOCl and but-1-ene to form 1-chlorobutan-2-ol, including curly arrows, lone pairs and dipoles where appropriate. [2] (iii) The product of the reaction, 1-chlorobutan-2-ol, exists as a mixture of stereoisomers. State the type of isomerism that occurs and briefly explain how and in what proportion the stereoisomers were formed. [3]

3 2018 HCI C1 H2 Chemistry Promotional Exam / Paper 3 (iv) Compounds A, B and C have the same molecular formula C8H8. All three compounds possess a six-membered ring each. When all three compounds undergo oxidative cleavage separatel