Lab Manual- Experiment 1

Lab Manual- Experiment 1 - unknown based on the...

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EXPERIMENT 1: MELTING POINT Reference: Techniques 9, pp. 643-652, Pavia et al. INTRODUCTION: Melting Point Ranges The melting point is the ultimate criterion of the purity of a solid since pure compounds melt within very precise temperature ranges. Your lab instructor will explain to you the use of the melting point apparatus as well as show you how to fill the melting point capillary. Part A: Determine the melting point of the following and observe the changes due to the "impurity" present. a. trans -Cinnamic acid b. Urea c. a 1:1 mixture of both trans -Cinnamic acid and Urea. Record your observations. Part B: Identify unknowns by comparing the melting point ranges of pure substances with that of their mixtures Measure and record the melting point ranges of compounds labeled A or B, which are pure samples of either cholesterol or 3-nitrobenzoic acid. Mix small portions of your unknown with an equal quantity of each known compound (cholesterol or 3-nitrobenzoic acid). Measure and record the melting range of the mixtures. Record your observations and identify your
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Unformatted text preview: unknown based on the experimental evidence. Part C: Determine the melting range of an unknown compound given by your instructor. The unknown compound is one of the following. Compound Melting Range/°C Compound Melting Range/°C Naphthalene 80-82 4-Methoxybenzoic acid 182-185 Anthracene 216-217 1-Naphthol 95-96 Benzoic acid 122-123 3-Nitroaniline 112-114 Benzophenone 49-51 4-Nitrophenol 112-114 p-Bromoacetanilide 165-169 3-Nitrobenzoic acid 140-143 Cholesterol 147-148 Salicylic acid 159-160 4-Chlorobenzoic acid 239-242 o-Toluic acid 103-105 Cinnamic acid 133-135 p-Toluic acid 180 Part D: Confirm the identity of the unknown compound from Part C by recording a mixed melting point measurement with a reference sample provided by your lab instructor. This is a routine part of any melting point procedure and should always be performed as long as a reference sample is available. You should try to remember this for later experiments....
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Lab Manual- Experiment 1 - unknown based on the...

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