CHM 117 - Lab 1 Spring 2018 PDF

Preview

Summary

Download CHM 117 - Lab 1 Spring 2018 PDF

Description

CHM 117 Experiment Discussion (50 points scale) Title: Classification and Identification of Hydrocarbons

Purpose: The purpose of this experiment is to identify the physical and chemical properties of hydrocarbons. For physical properties the principles of solubility and density are to be investigated. For chemical properties different tests are to be used to compare the chemical reactivity of an alkane, alkene, and an aromatic compound. The tests to be done include the bromine, KMnO4, and H2SO4 tests. After this is done identify the unknowns that were used in this experiment.

Fundamental principle or theory behind the experiment: Hydrocarbons are compounds that only contain carbon and hydrogen. These hydrocarbons can be classified further by the type of bonds that they contain. If a hydrocarbon contains only single bonds, it is an alkane. If it contains one or more carbon-carbon double bonds, it is classified as an alkene. If it contains one or more triple bonds between two carbon atoms, it is an alkyne. If it contains a benzene ring, it is considered aromatic. These types of compounds react in different ways, so it is possible to distinguish between them using experimental tests. All balanced chemical equations and formulas are included in the laboratory manual on pgs. 3 and 4. These include the chemical equations and formulas for combustion, reaction with bromine, reaction with concentrated sulfuric acid, and reaction with potassium permanganate.

Method: Before you begin it is important to make sure that all the chemicals and equipment that are necessary to complete the experiment are available. The chemicals and equipment that will be used this week include 1% neutral aqueous KMnO4, 1% Br2 in cyclohexane, blue litmus paper, concentrated H2SO4, cyclohexene, hexane, aluminum chloride, test tubes (100 x 13mm), ligroin, toluene, unknowns A and B, watch glasses, and ice. First, the physical properties of hydrocarbons were tested. To understand the physical properties of hydrocarbons, we needed to understand the concepts of both solubility and density. A description of both are listed in the laboratory manual. The solubility of the hydrocarbons was tested in both H20 and ligroin. The density of hydrocarbons was to be tested in both H20 and ligroin as well. Second, the chemical properties of hydrocarbons were tested. In this experiment hexane, cyclohexene, toluene, and two unknowns were used. The combustion test was not used for this laboratory. The bromine test, KMnO4 test, and H2SO4 test are to be used to compare the chemical reactivity of an alkane, alkene, and an aromatic compound. Lastly, analyze the results to determine the identity of Unknown A and Unknown B.

Results/Data: Attached to this page are the results/data that my partner and I received for this laboratory. These are discussed in the section below. A summary of the results relating to the physical properties of hydrocarbons are as follows: 

In H20 the hydrocarbons are all insoluble and density is less than 1.



In ligroin the hydrocarbons are all soluble and have a density that is equal to 1.

A summary of the results relating to the chemical properties of hydrocarbons are as follows: 

Combustion was not used.



Hexane, toluene, and Unknown A all had a negative reaction to the bromine, KMnO4, and H2SO4 tests.



Cyclohexane and Unknown B had a positive reaction to the bromine, KMnO4, and H2SO4 tests.



Unknown A is hexane and Unknown B is cyclohexene.

Discussion and Conclusion: “Classification and Identification of Hydrocarbons” taught how identify the physical and chemical properties of hydrocarbons. For physical properties the principles of solubility and density were investigated. For chemical properties different tests were used to compare the chemical reactivity of an alkane, alkene, and an aromatic compound. The tests that were done included bromine, KMnO4, and H2SO4 tests. The results/data are listed in the table attached prior to this page. The manual, with the steps included, guided my partner and myself. First, the physical properties of hydrocarbons were tested. To understand the physical properties of hydrocarbons, we needed to understand the concepts of both solubility and density. It was found there was no solubility in H20 with the hydrocarbons of hexane, cyclohexene, toluene, and the unknowns. The hydrocarbon did not mix with the solvent and therefore was considered insoluble. Next, density was to be identified in H20 and it was found that all the hydrocarbons had a density that was less than 1. If the density was found to be less than water this means that it floats. If the density was found to be greater than water, then this would mean that it would sink. In this scenario the hydrocarbons all floated in H20. Next, the solubility of ligroin was to be tested. It was found that the hydrocarbons of hexane, cyclohexene, toluene, and the unknowns were all soluble. The hydrocarbon mixed with the solvent and therefore was considered soluble. Next, density was to be identified in ligroin and it was found that all the hydrocarbons had a density that was equal to 1. The next part of this experiment was to test the chemical properties of hydrocarbons. In this experiment only hexane, cyclohexene, toluene, and only two unknowns were used. The combustion test was not used for this laboratory. The bromine test was used and was found to have a negative effect on hexane, toluene, and unknown A. The results were found to be negative after adding the bromine solution and the red/brown color persisted. The test was found to have a positive effect on cyclohexane and unknown B. The results were positive because after adding the bromine solution the color was clear. Next, the KMnO4 test was used and was found to have a negative effect on hexane, toluene, and unknown A. The

results were found to be negative after adding the 1% aqueous KMnO4 solution and the purple color persisted. The test was found to have a positive effect on cyclohexene and unknown B. The results were positive because after adding the bromine solution the color was brown. Lastly, the H2SO4 test was used and was found to have a negative effect on hexane, toluene, and unknown A. The results were found to be negative after adding the concentrated sulfuric acid solution and no color occurred, meaning no reaction. The test tubes were all clear at the end of the negative results. The test was found to have a positive effect on cyclohexene and unknown B. The results were positive because after adding the sulfuric acid solution the color was light brown, indicating a reaction occurred. After analyzing the results Unknown A was identified as hexane and Unknown B was identified as cyclohexene. Errors could have taken place in this experiment that would have changed the results, but I believe that none have. Some of the errors that could have happened include using the wrong hydrocarbon, documentation errors, or misunderstanding the steps provided by the instructor and laboratory manual. In conclusion, after testing both the physical and chemical properties of hydrocarbons a greater knowledge was gained about this subject. The pages that are attached to this laboratory report include the results found. This laboratory was necessary in understanding the topic of classifying and identifying hydrocarbons. If this laboratory had to be conducted again I’d be able to repeat this experiment and would receive the same results with no errors....