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College of Engineering, Science and Technology School of Sciences Natabua Campus PO Box 5529 Lautoka (FIJI) CHM 703 Laboratory Lab Reports Unlike your notebook, a report is intended for someone else's eyes. It should present the background of the experiment, state the experimental procedure in a manner that allows it to be reproduced, and discuss and summarize the results, all preferably in a format familiar to every professional working in the discipline. The format of the report will be approximately, that of a research paper in a chemistry journal. Every report will therefore be an exercise in scientific writing. Scientific writing should be clear and organized. Say exactly what you mean as simply and accurately as you can. Be brief. Don't be verbose or stilted. However, do get used to the scientific terms commonly used to describe certain operations, e.g., refluxed, filtered, recrystallized, distilled, etc. Learn the jargon and be consistent in the use of units, names, abbreviations, tense, etc.. This will actually shorten your report and make it easier to write. The total length of each report should not exceed about 4 pages, including the title page. In general, and always when describing the experimental procedure, use the Third Person, the Passive Voice and the Past Tense (e.g., "sodium acetate was added to the reaction mixture," not "I added sodium acetate to the reaction mixture," or "add sodium acetate to the reaction mixture.”) Although this is not a class on writing skills, I expect all reports to be written in good, grammatical English. Handwritten reports are acceptable as long as your handwriting is legible. However, I strongly recommend using a word processor. Note: do not write the lab report in your lab notebook. 1. 2. 3. 4. Your report should be written in a format that consists of the following sections: Title page Introduction / statement of objectives. Experimental procedure / results. Discussion. 1 Title Page This page should have on it the title of the experiment, the date(s) on which it was done, and your name, FNU ID number, and College. Introduction This should begin on a new page, and should include a statement of your objectives (i.e., the purpose of your experiment), an outline of the theory involved, including chemical equations for any reactions, and possibly a brief discussion of why the technique is interesting or important. The whole thing should occupy no more than half a page. Don't give a detailed experimental procedure under the guise of an introduction. This is a very common error, for which no credit will be given. Experimental Section This should consist of a very concise description of what you actually did. Remember to use the Third Person, the Passive Voice and the Past Tense. DO NOT RE-WRITE THE PROCEDURE GIVEN IN A LAB HANDOUT OR A TEXTBOOK. Where relevant, include numerical data (how much starting materials, solvent, etc. you used, weights, volumes, spectroscopic data if any, etc.). Be sure to include your final experimental results, showing your calculations, and expressing numerical results to the correct number of significant figures, based on your estimate of the experimental uncertainty. All this information should be presented in such a way that another person can repeat the experiment in virtually the same way. Results and Discussion Very little numerical calculation is required in most organic chemistry experiments. However, every synthesis experiment must include a percentage yield, usually expressed to two, at most three, significant figures (i.e., at most one decimal place, but usually none). This is calculated using the formula number of moles of product percentage yield = number of moles of limiting starting material x 100. For the experiments you will be doing in this course, very little discussion will be needed, especially if all goes as planned. If you data needs to be interpreted, this is the place to do it. If a problem arises (a poor yield, a yield in excess of 100% (!), a synthesis that failed to work) attempt to explain it here. If you can think of a better way to do the experiment, make your suggestions here. 2 Sample Lab Report Synthesis of 2-Chloro-2-methylbutane from 2-Methyl-2-butanol Introduction 2-Methyl-2-butanol, also known as tert-amyl alcohol, is a tertiary alcohol that undergoes a facile reaction with conc.HCl to give the corresponding alkyl halide, 2-chloro-2-methylbutane, via a mechanism that involves the formation of a stable tertiary carbocation. The reaction is much less easy with primary and secondary alcohols. The objective of this experiment was to synthesize the product, and to study the techniques of extraction and distillation used to purify it. Experimental Procedure 2-Methyl-2-butanol (27 mL, 0.25 mol) and conc. HCl (65 mL) were shaken together in a 125 mL separatory funnel for several minutes, then allowed to stand for 15 minutes, during which time 2 layers separated. The lower (aqueous) layer was drained off, and the upper layer (product) was washed with 20 mL of 5% NaHCO3 solution (to remove excess acid) and with 20 mL of water. It was then dried with anhydrous CaCl2 and purified by simple distillation (b.p. 85°C). The yield was 17.2 g (65%). Discussion The procedure was operationally very straightforward. Since the reaction is reversible, a better yield could perhaps be obtained by using gaseous HCl rather than the aqueous acid, but this may entail special techniques. 3