The Purity and Purification of Solids Recrystallization Lab Essay examples

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Pages: 7

The Purity and Purification of Solids

In this experiment, impure adipic acid is purified though recrystallization. The impure adipic acid is dissolved in a solvent. After cooling it is ran through a vacuum filter to separate any moisture. The dry crystals are then weight for percent yield and the melting point range is taken to test the purity. There were two different trials ran in this experiment. The difference between the two was the addition of charcoal in the initial step to remove color impurities. For part A (without charcoal) the initial impure weight was 1.0256g. After the filtration, the final pure product weighted 0.6063g which is a 59.17% yield. The Melting point range for part A was 151.1°C
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In part A, the blue color was never removed so that added weight to the final dry weight. For part B, the blue color was removed so the weight of the final dry crystals was lighter.
The melting point of part A was 152.1°C – 154.9°C. This is accurate because the temperature was slightly higher than 2°C due to the impure blue color. Whatever causes the crystals to be blue must be a slight impurity because it increases the melting point range. For part B, the melting point was 153.0°C to 155.0°C. This was accurate because the melting point was 2°C. Pure substances have a sharp melting point of less than or equal to 2°C. Part B’s melting point fit in this category. The melting point of the impure adipic acid was also taken. It was 151.1°C – 156.8°C. This melting point range was a lot higher than 2°C and clearly meant that impure adipic acid was impure.

The range in melting point for Part B was sharp, which indicated that the purification was successful. The Percent yield however was low so there has to be improvements somewhere in the steps of purification. The only difference between Part B and Part A was the addition of charcoal in the initial steps. The addition of charcoal helped to remove the color, which is an impurity and a possible cause for increase temperature range and increased weight. The final dry crystals of part A had this color still stained within it. This could explain why Part A