RI Prelim P2

RAFFLES INSTITUTION (JUNIOR COLLEGE) PRELIMINARY EXAMINATION 2009 Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9746/02 Paper 2 Structured Questions 23 September 2009 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces provided on the top of this page. Write in dark blue or black pen in the spaces provided. 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 all questions. A Data Booklet is provided. Do not write anything on it. 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. For Examiner’s Use This document consists of 14 printed pages. Question 1 2 3 4 5 Total Marks /10 /14 /11 /11 /14 /60

2 © RAFFLES INSTITUTION (JUNIOR COLLEGE) 2009 9746 / 02 / 09 [Turn Over x y z Answer all questions in the spaces provided. 1 Fluorine is the most reactive of all elements and even combines with all noble gases except helium and neon. Compounds containing the element f luorine are commonly called fluorides. (a) (i) Give the electronic configuration of fluorine, F. (ii) On the axes below, sketch the shape(s) of the sing ly–occupied orbital(s) in an atom of F at ground state. [2] (b) With reference to the Data Booklet , briefly explain the following statements. (i) The first ionisation energy of oxygen is lower than that of fluorine. (ii) The second ionisation energy of oxygen is higher than that of fluorine. [3] For Examiner’s Use

3 © RAFFLES INSTITUTION (JUNIOR COLLEGE) 2009 9746 / 02 / 09 [Turn Over (c) It is well known that fluoride, F – , helps prevent tooth decay. Hence, it is commonly added to toothpastes, mouth rinses and water suppli es via water–soluble compounds such as sodium fluoride. However, in high concentrations, F – is lethal. Historically, most cases of fluoride poisoning have been caused by the accidental ingest ion of insecticides containing F – but currently, most cases have been due to the swallowing of toothpaste. A suggested method of treatment in the case of acc idental ingestion is to give the person some milk of magnesia , which is an aqueous suspension of magnesium hydroxide, Mg(OH) 2(s). (i) Given that stomach juices are highly acidic, writ e a balanced equation, with state symbols, for the reaction that occurs when some milk of magnesia ente