NYJC_H2 Chem Prelim 08 P3

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 9746/03 Paper 3 Free Response 10 September 2008 2 hours Candidates answer Section A on the Question Paper Additional Materials: Answer Paper Data Booklet Graph Paper 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 any four questions. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 2 3 4 5 Section B Answer all questions on separate answer paper. Total This document consists of 10 printed pages and 2 blank pages. [Turn over

2 BLANK PAGE H2 Chemistry 9746/03 NYJC J2/08 PX [Turn over

3 Answer any four questions. 1 Some organic and inorganic compounds are classified under a category called ‘Non-Existent Compounds’. They are called non-existent because so far chemists had been unable to synthesise them. Some of the reasons why these compounds are unstable are: • unfavourable bond energy terms • a redox incompatibility of the ions making up the compound • inability of the element concerned to pr ovided orbitals of suitable energy for effective bond-forming overlap with neighbouring atoms • reaction occurring between the ions For the following cases, suggest an explanation for each observation. You may use data from the Data Booklet to assist you in your answe rs. Give relevant equations to support your answers. (a) Both phosphorus and nitrogen are elements in Group V of the Periodic Table. PCl5 can be formed but not NCl5. [ 3 ] (b) It is possible to find MnCl2 in the laboratory but impossible to get MnCl3. [3] (c) When aqueous sodium carbonate is added to aqueous aluminium chloride, a colourless gas is liberated and the precipit ate formed is not aluminium carbonate, Al2(CO3)3. [ 5 ] (d) Caprolactum, a monomer of t he polymer nylon 6, exists as an alicyclic ring structure and not as 6-aminohexanoic acid, a straight chain aliphatic st ructure as most monomers do. O H C N H 2NCH2CH2CH2CH2CH2CO2H Caprolactum 6-aminohexanoic acid [4] (e) Hydration of ethyne, H−C C−H, should produce ethenol, H−C=C−H H OH but, instea