RI_Prelim_H1_P2

1 © RAFFLES INSTITUTION (JUNIOR COLLEGE) 2009 8872/P02/09 [Turn Over CANDIDATE NAME CLASS INDEX NUMBER RAFFLES INSTITUTION (JC) PRELIMINARY EXAMINATION 2009 HIGHER 1 CHEMISTRY 8872/02 Paper 2 23 September 2009 2 hours Candidates answer Section A on the Question Paper Additional Materials: Answer Booklet/ Paper Data Booklet Graph Paper READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write your name, class and index number in the spaces provided on the cover page. 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 paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer any two questions on separate answer paper. 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 B6 B7 B8 Total This document consists of 15 printed pages. Raffles Institution Junior College

2 © RAFFLES INSTITUTION (JUNIOR COLLEGE) 2009 8872/P02/09 [Turn Over Section A (40 marks) This section consists of 5 questions. Answer all questions in the spaces provided. 1. Hydrazine is a hydride of nitrogen with the formula N 2H4. It is a colourless liquid with an ammonia-like odour and is derived from the same ind ustrial chemistry processes that manufacture ammonia. However, hydrazine has physical properties that are more similar to water. It can behave as a weak monoacidic base, forming salts with the more common mineral acids, like sulfuric acids. Hydrazine is a strong reducing agent. Warming hydr azine with nitric acid results in the reduction of nitric acid to nitrogen monoxide, NO w hile hydrazine is oxidised to nitrogen, N 2. A variant of hydrazine, methylhydrazine CH 3NHNH 2, when mixed with dinitrogen tetraoxide, N 2O4, is used as a rocket fuel as this gives a highly exothermic reaction. (a) Draw a dot-and-cross diagram for hydrazine. State t he shape for the hydrazine molecule around the nitrogen atom and the bond angle of H − N− H. [3] (b) Hydrazine can react with sulfuric acid to give a sa lt, hydrazine sulfate, (N 2H5 +)(HSO 4 − ). Explain, with the aid of an equation, if an aque ous solution of hydrazine sulfate is acidic, neutral or basic. [2] For Examiner’s Use

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