HCI 2016 C1 Promotional Exam Paper 3

This document consists of 8 printed pages. HWA CHONG INSTITUTION C1 Promotional Examination Higher 2 NAME CT GROUP 16S CHEMISTRY Paper 3 Free Response Candidates answer on separate paper. Additional Materials: Answer Paper, Graph Paper, Cover Page and Data Booklet. 9729/03 30 September 2016 1 hour 20 minutes 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 Answer all questions. Section B Answer one question. 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 2016 HCI C1 H2 Chemistry Promotional Exam / Paper 3 Section A Answer all the questions in this section. 1 (a) When 2-methylbutane is reacted with chlorine gas in the presence of sunlight, several mono‑chlorinated products are formed. (i) Draw the structures of all possible mono-chlorinated products. [2] (ii) Explain which of the products you have drawn in (i) was formed via the most stable radical. [1] (iii) Hence, describe the mechanism for the formation of the product you identified in (ii). [3] (b) A student has forgotten to properly label bottles known to contain the following two organic compounds: Compound A Cyclopenta-1,3-diene B 2-methylbut-2-ene Describe a simple chemical test that would allow the student to distinguish between A and B. [2]

3 2016 HCI C1 H2 Chemistry Promotional Exam / Paper 3 (c) A 2.00 g impure sample of yttrium(III) oxide, Y2O3 (Mr = 225.8), was known to be contaminated with a little hydrated yttrium(III) carbonate, Y2(CO3)3•3H2O and other inert material. After the sample was left exposed to moist air for several days, it was reweighed and found to have increased in mass. The change in mass was due to the conversion of some of the oxide to form compound Q. The resulting sample was completely dissolved in 35.00 cm3 of 2.00 mol dm−3 hydrochloric acid, releasing 16.40 cm3 of gas (measured at standard temperature and pressure) in the process. After all the gas was released, the resulting solution required 19.65 cm3 of 1.00 mol dm−3 sodium hydroxide solution for complete neutralisation. The following information may be relevant:  Balanced equation for reaction of yttrium(III) oxide with hydrochloric acid: Y2O3 + 6HCl → 2YCl3 + 3H2O  Q is made up of yttrium, oxygen and hydrogen only.  When separately reacted with a mineral acid, Q and yttrium(I