NJC_Prelim_CHEM_P2

NJC Preliminary Examination 9647/02/15 NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper. Additional Materials: Data Booklet 9647/02 Friday 28 August 2015 2 hours READ THESE INSTRUCTIONS FIRST Write your subject class, registration number and name 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 paper clips, highlighters, glue or correction fluid/tape. Answers all questions. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 /12 2 /12 3 / 7 4 /15 5 / 8 6 /13 7 / 5 Total /72 This document consists of 20 printed pages

2 NJC Preliminary Examination 9647/02/15 For Examiner’s Use Answer all the questions 1 Planning (P) The label on a bottle in your school chemistry laboratory is found to be missing and you are to help identify the organic compound in the bottle. The compound in the bottle is one of the following:  ethanal  propanamide  1-iodopentan-2-one  benzaldehyde  phenylamine (a) Plan a series of simple chemical tests that would allow you to confirm the identity of the compound in the bottle through a positive test. You are reminded that most of the compounds listed are flammable liquids. Your plan must include the following: ‐ the reagents and conditions to be used, but not the quantities of reagent used. ‐ observation(s) for each test. [6]

3 NJC Preliminary Examination 9647/02/15 [Turn over For Examiner’s Use (b) Assuming the unknown compound to be ethanal, it can react with 2,4-dinitrophenylhydrazine (2,4-DNPH) to fo rm a crystalline solid derivative (melting point 165 C). (i) Draw the displayed formula of the derivative formed between ethanal and 2,4-DNPH. [1] (ii) Write a plan for the preparation of the 2,4-DNPH derivative of ethanal. In your plan you should: − give a full description of the procedure you would use to prepare and purify the derivative; − explain how you would check the purity of your sample. …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………………………… …………….……………………………………………………………………