The Purity and Purification of Solids-Melting Point Essay

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Introduction: The method for purifying solids is done by observing the melting point. This is important because if there is an impure substance the melting point would be depression and the melting range would be broader. By finding the melting point of a known substance one can then observe an unknown substance’s melting point to see if the points are the same and try to figure out the unknown.

Experimental Section: The first known substance we used was Biphenyl. 68 degrees Celsius is the known melting point. We used the capillary method and observed the melting point using a Mel-temp device. The next substance whose melting point we observed was 90 % Naphthalene, 10 % Biphenyl. In the last part of the experiment I observed the
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Melting Point (Celsius) Melting Point Range (Celsius)
Trial One 112.1 102.1-112.1
Trial Two 114.7 106.-114.7
Trial Three 114.4 107.1-114.4

The next table shows the melting points of the mixtures made to determine the Unknown. Melting Point (Celsius) Melting Point Range (Celsius)
Trial One: 2-Chloracetamide and Unknown E 117.2 80.8-117.2
Trial Two: 2-Chloracetamide and Unknown E 118.1 81.8-118.1
Trial One: Acetanilide and Unknown E 115.1 106.7-115.1
Trial Two: Acetanilide and Unknown E 113.6 102.0-113.6

Discussion: In part A the melting points I observed were similar to those of my classmates. During the first trial the temperature was climbing quickly and the Biphenyl melted quickly. During the next two trials the Mel-temp was set at a lower setting and our melting point was closer to the known melting point.

Conclusion: I have determined that Unknown E is Acetanilide. The melting point of the mixtures was very close to the melting point of plain Unknown E. The 2-Chloracetamide and Unknown E’s mixture had to high of a melting point. Based on my results and observations I would conclude that Unknown E is Acetanilide.

Fessenden, Fessenden, and Feist. Organic Laboratory Techniques. 3rd Edition. Brooks/Cole. Pacific Grove, CA. 2001. Pgs. 39-46.
Organic Chemistry Laboratory 1, CH
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