Post Lab - Simple and Fractional Distillation 1. From the boiling point vs. volu
ID: 554486 • Letter: P
Question
Post Lab - Simple and Fractional Distillation 1. From the boiling point vs. volume graph from the simple distillation, what can you conclude about the purity of the distillate? Hint: How would one determine if a pure compound is dripping into the collection vessel? 2. From the boiling point vs. volume graph from the fractional distillation, what can you conclude about the purity of the distillate? 3. What is the basis for the difference in separation between simple distillation and fractional distillation? 4. A mixture of two miscible liquids with a widely different boiling point is distilled. The temperature of distilled liquid is observed to plateau and then drop before rising again. Explain the temperature drop. 73Explanation / Answer
1. From a boiling point versus volume graph for a simple distillation, once the pure liqis starts to come off, the boiling point reaches to a constant value and does not change until all of the pure liquid has come off the distillation vessel. If the boiling point fluctuates or is either below or above the actual boiling point of pure compound, it is not pure enough to start collection. Once the boiling point reaches a constant vaue, the liquid can be collected by dripping into the collection flask.
2. For fractional distillation with more than one component liquid inside the distillation flask, the boiling point initially rises, reaches a constant value once the first pure fraction starts to get collected. The temperature remains constant until the first fraction keeps comming. Once the fraction gets over, the temperature rises again and reaches the second constant value corresponding to the second fraction in the distillate. The constant boiling point is an indication of purity of the fraction.
3. When we have only one major fraction with very small impurity in the liquid whose boiling point is a lot differ than the fraction of our choice, we use simple distillation to purify the liquid. On the other hand, when we have more than one component in the distillation unit. The components are not minor to each other, we use fractional distillation to separat them from each other.
4. In the distillaion of two miscible liquid. After the first disllate is collected the temperature drops before rising again. This is because the heat supplied is just enough the distill the first fraction intially and more heat is required to raise the temperature of the distillate now. The drop indicates the first fraction has completely come off from the mixture.