My unknown sample was number 18. I did three melting point trials, which resulted in a melting point range of approximately 120°C to 122°C, as shown in Table 1. I also did two mixed melting point trials using Benzoic Acid and Succinimide, as shown in Table 2. Percent recovery is 28.26 grams.
Table 1: Unknown Melting Point Trials
120°C – 122°C
120°C – 122°C
119°C - 122°C
Table 2: Mixed Melting Point Trials
Benzoic Acid MP
Unknown #18 MP
122°C – 128°C
122°C – 126°C
121°C – 127°C
122°C - 1227°C
122°C - 126°C
120°C - 128°C
My unknown was number 18. I did three mixed melting point trials that resulted in a melting point of 120°C to 122°C. The melting point range is small, which indicates a relatively pure substance. I did a mixed melting point trial to find out what substance I had. I used Benzoic Acid and Succinimide because they were the two substances in my melting point range. Just by comparing the characteristics of the two substances to my unknown, I assumed it to be Benzoic Acid. My unknown and Benzoic Acid had a fine, powdery texture to it, while Succinimide looked like crystals. The two mixed melting point range trials confirmed this. Unknown number 18 is Benzoic Acid. A possible alternative would be Succinimide, because of the close melting points. Another possible alternative is Fluorene, which melts at slightly lower temperatures than my unknown does. Benzoic Acid is C7H6O2. Its structure is:
My percent recovery was 28.26%. During the dissolving of my unknown, there was still undissolved solid. This could have led to a smaller percent recovery. If you are not given the solubility data for your compound, then you must test for the solvent required. This is done by mixing the possible solvent and your solid together and agitating it, heating it, then cooling it. It crystals form, you have your solvent. You dissolve your solid by using a hot solvent, and then cool...
References: Alfa Aesar. "ChemSpider | The Free Chemical Database." ChemSpider | The Free Chemical Database. Royal Sociey of Chemistry, n.d. Web. 10 Sept. 2013.
Zubrick, James W. The Organic Chem Lab Survival Manual: A Student 's Guide to Techniques. 8th ed. Hoboken, NJ: Wiley, 2011. Print.
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