MP of Compounds and Mixtures

➢ The following information is taken from the lab.
Pure Benzoic Acid
Temperature when the sample starts to melt (°C): 121
Temperature when the sample has completely melted (°C): 123
Pure Mandelic Acid
Temperature when the sample starts to melt (°C): 118
Temperature when the sample has completely melted (°C): 119
80:20 mixture (benzoic acid:mandelic acid)
Temperature when the sample starts to melt (°C): 93
Temperature when the sample has completely melted (°C): 101
60:40 mixture (benzoic acid:mandelic acid)
Temperature when the sample starts to melt (°C): 92
Temperature when the sample has completely melted (°C): 96
40:60 mixture (benzoic acid:mandelic acid)
Temperature when the sample starts to melt (°C): 89
Temperature when the sample has completely melted (°C): 91
20:80 mixture (benzoic acid:mandelic acid)
Temperature when the sample starts to melt (°C): 87
Temperature when the sample has completely melted (°C): 89

Report Table MP.3: Melting pont analysis Midpoint of melting temperature (MP) range for pure compounds and mixtures Start of MP temp range (°C) End of MP temp range (°C) Midpoint of MP temp range (°C) Pure benzoic acid 121 123 122 80:20 mixture (benzoic acid:mandelic acid) 93 101 97 60:40 mixture (benzoic acid:mandelic acid) 92 96 94 40:60 mixture (benzoic acid:mandelic acid) 89 91 90 20:80 mixture (benzoic acid:mandelic acid) 87 89 88 Pure mandelic acid 118 119 118.5 ➢ Please use the above information to answer the following questions, please show your work: 1. Graph your results of the pure compound and mixture melting points. For each point, use the temperature in the middle of your melting point range. After plotting all the points, draw two best fit straight lines to connect at the eutectic composition. (please add an excel graph) 2. What is the melting point of benzoic acid that you determined? How does this compare to the literature value? 3. What does this tell you about the purity of the compound? 4. Based on the intersection of the lines from your graph, what was the eutectic temperature for the mixture?
5. Based on the intersection of the lines from your graph, what was the composition of the eutectic mixture?