Melting Point Determination Essay

Identifying an unusual change can be a difficult task. In distinguishing a chemical rise, researchers often measure several somatogenic properties melt engineer, boiling summit, meanness and observes a few chemic properties reactivity, acidity, basicity of the unite. The reason for determining several chemical and sensible properties of the compound is that it is quite potential for two different compounds to live a few sensible and or chemical properties in car park but it is highly unlikely for the two compounds to make up very umpteen identical physical and chemical properties (Gilber & Martin, 2010).The goal of this experiment is to discover the identity operator of the outlander using the break up- office technique. If the entire compound in the list disposed(p) by your instructor had distinctly different melt down demonstrates, it would be possible to get back the identity of the unknown by just taking its dissolve mind. However, from separately mavin of the compounds in this list has a melting point that is close to the melting point of another compound in the list. Therefore, the melting point of the unknown volition allow you to break down the choices to two compounds (Pavia, Lampman, & Kriza, 2013).To determine the identity of you compound, you mustiness perform categorisation melting points of your unknown and each of the two compounds with similar melting points. A garland melting point that is depressed and has a wide tramp indicates that the two compounds in the mixture atomic number 18 different. It should be pointed out, however, that it is not possible to accurately predict the physical properties of newly synthesized or isolated compounds.Therefore, turn offs of physical properties are only recycresearch laboratoryle in identifying previously known compounds. However, useful information as to the compounds identity and its integrity can often be obtained from its melting point. Although the melting point can be utilise to help identify an unknown by comparing its melting point to literature values, it must be apparent that there are literally hundreds if not thousands of compounds that cover the same melting point. To solve this dilemma the identity of a compound can be confirm using coalesce melting point method.If you prepare a mixture of you unknown chemical and the mavin you comical it may be and measure the melting point of the mixture whence there are two possible results The melting point of the mixture is the same as the pure compound which means that the unknown compound and the known compound are the same. The melting point of the mixture is debase than either of the two pure components and the melting range is large. This is because the two compounds are different with the result that one is an impurity in the other (Dean, Jones, Holmes, & Reed, 2011). tendency of the temperature at which the solid and liquid phases of a substance are in equilibrium is time consuming. It is in like manner quite difficult with a lilliputian amount of standard. Thus, in practice, most melting points are determined as capillary melting points, which can be done quickly with a trivial amount of sample in a capillary underpass (Bettelheim & Frederick, 2004). Melting point summary is a quick, relatively easy, and inexpensive prelim analysis if the sample is already mostly pure and has a surmise identity. Additionally, analysis requires small samples only.As with any analysis, there are plastered drawbacks to melting point analysis. If the sample is not solid, melting point analysis cannot be done. Also, analysis is destructive of the sample. For qualitative identification analysis, there are now more specific and accurate analyses that exist, although they are typically lots more expensive. Also, samples with more than one solute cannot be analyzed quantitatively for purity (Molavi & Barron, 2011)MethodologyFinding an Identical CompoundTwo melting-p oint capillaries were filled with small amounts of your sample. One was apply to determine an approximate melting point range for your unknown by allowing the temperature to rise at about 6oC per minute. Then the melting point apparatus was cooled to at least 5oC below the temperature at which melting began.A slow, careful determination of the melting point range was make on the molybdenum sample by allowing the temperature to rise at a rate of approximately 2oC per minute. It is important that the melting point was measured cautiously because finding another student in the lab with the identical compound depends on it.The melting point range was record in the science laboratory notebook and also on the information sheet provided by the instructor along with the student number. From the data sheet, another student in the lab was located whose unknown has a melting point range that is at heart 4oC. A small amount of the students compound was used to prepare a sample for a blen d melting point. The actus reus range of 4oC was accounted for experimental error and the fact that the thermometers are not calibrate thus the ranges from different instruments may vary slightly.To prepare the mixed melting point sample, one part of the unknown given was used to one part of the other students compound. The sample was mixed good by gently crushing the mixture with a glass soul- inhalation rod until it looks homogeneous. The melting point range was determined and the result was recorded in the laboratory notebook.Search was continued until you identified a student in the lab with a compound identical to yours and a second student in the lab with an unknown with approximately the same melting point range, but whose compound is not the same as yours.Results and handlingTable 1 Mixed Melting Point Unknowns Unknown organise Melting Point Range (oC) Benzoic Acid pic 121-123 DL-malic Acid pic 131-133 carbamide pic 132-135 Trans-cinnamic Acid pic 131-136 Succ inic Acid pic 184 Table 1 shows the given unknowns to be identified in this experiment. The melting point range in the table was the basis of the researchers in identifying their given unknowns. Some chemical compounds given from the manual of arms was omitted to limit the scope of the experiment. Other books give different melting point range on the compounds in the table. This is because temperature also varies in the fact that the thermometers are not calibrated.The unknown pure compound has a white powdered solid feature. Melting point range determination is only relevant for solid compounds. Two running games were conducted to observe the melting point of the pure compound. For the world-class trial, it was observed that the compound starts to melt at exactly 135oC and the solid in the capillary tube was completely dissolved at 137oC.The solid melts instantly because the temperature of the cooking oil used arises rapidly compared when using water as a boiling bath. The sec ond trial was conducted to confirm if the result for trial one is precise and the finding for the melting point also ranges from 135-137oC. From the data collected, it was predicted that the unknown might be urea or trans-cinnamic acid. Since both urea and trans-cinnamic acid have exactly the same melting point, it is difficult to determine which one is the given compound.The pure compound (Unknown A) was mixed to the compound (Unknown B) of one student with melting-point range of 134-136oC. Both unknown have the same physical feature which fell into conclusion that the two solids are same compounds. However, the temperature of the mixed compounds decreased by 80-84oC. Possible reason for this outcome is contamination of the mixed compound by the stirring rod used in mixing. struggle two was conducted for the mix-melting point determination. Another student whose compound (Unknown C) has a melting point that ranges from 131-134oC was mixed with Unknown A. Both unknowns have the same physical feature with Unknown B. The unknowns were mixed thoroughly with a clean stirring rod. The mixed compound starts to dissolve at exactly 134oC and solid in the capillary tube was completely dissolved at a temperature of 136oC.It is smashed evidence that the two substances are the same. According to Mayo, Pike, and Forbes (2011), the crystalline lattice forces safekeeping organic solids together are distributed over a relatively peg energy range. The melting points of organic compounds, therefore, are usually relatively sharp, that is, less(prenominal) than 2oC. The range and maximum temperature of the melting point, however, are very sensitive to impurities. underage amounts of sample contamination by soluble impurities nearly always will result in meting-point depression. The drop in melting point is usually accompanied by an expansion of the melting-point range.Thus, in addition to the melting point acting as a useful guide in identification, it also can be a particul arly effective indication of sample purity. The effectiveness of this technique depends on the relative solubility of the substances in each other. The usefulness of mixed melting points is limited in that you must have some idea of the chemical nature of your unknowncompound and a sample of the suspected compound must be available.The researcher used melting points to determine the purity of organic compounds. Pure compounds were seen to have a narrow melting range, while impurities were seen to cause the melting range to fix lower and broader. From the mixture melting points the researcher definitively able to identify the unknown as trans-cinnamic acid.5. ReferencesAldrich, S. (n.d). Retrieved July14, 2013, from LLC, Sigma-Aldrich Co, http//www.sigmaaldrich.com/catalog/ product/aldrich/w228826?l ang=enion=PHBettelheim, Frederick, A., Landenberg, & Joseph M. (2004). positive and Biochemistry (5th ed.). USA A Division of Thomson Learning, Inc. Pages 17-20Dean, J., Jones, M., Holme s, D., & Reed, R. (2011). Practical Skills in Chemistry (11th ed.). England Pearson tuition Limimited.Gilbert, J. & Martin S. (2010). Experimental Organic Chemistry A Miniscale and Microscale onward motion A Miniscale and Microscale Approach (5th ed.). USA Cengage LearningMayo, D., Pike, R., & Forbes, D. (2011). Microscale Organic Laboratory with multistep and multiscale synthesis (5th ed.). United States posterior Wiley & Sons, Inc.Molavi, S., & Barron, A. (2012, May 29). Melting Point Analysis. Retrieved from the Connexions Web site http//cnx.org/content/m43565/1.1/Pavia, D., Lampman, G., Kriz, G., and Engel, R. (2013). A Microscal Approach to Organic Laboratory Techniques (5th ed.). USA Cencage Learning.