Shown below is a schematic representation of the water-ethanol phase diagram.
Making reference to the phase diagram, explain in a few sentences how one could enrich a solution of 15 percent ethanol - 85 percent water to a composition of 60 percent ethanol - 40 percent water. Be qualitative in your description, not quantitative.
Furthermore, explain why this procedure could not be used to reach a completely pure composition of 100 percent ethanol.
To enrich a solution of 15 percent ethanol - 85 percent water to a composition of 60 percent ethanol - 40 percent water, you can use a process called distillation. Distillation takes advantage of the different boiling points of the components in the solution.
First, heat the solution, and as it reaches its boiling point, the ethanol (which has a lower boiling point than water) will start to evaporate. This vapor, containing more ethanol than the original solution, is then collected and condensed. By collecting and condensing the vapor, you separate the more concentrated ethanol from the remaining solution.
Repeat this distillation process multiple times, and each time, you will collect a vapor with a higher ethanol concentration. By repeating the steps, you can gradually increase the ethanol concentration until you reach the desired composition of 60 percent ethanol - 40 percent water.
However, this procedure cannot be used to reach a completely pure composition of 100 percent ethanol because ethanol forms an azeotrope with water. An azeotrope is a mixture that has a constant boiling point and composition. In the case of ethanol-water, the azeotrope is approximately 95 percent ethanol - 5 percent water.
When the vapor of this azeotrope is distilled and condensed, it results in a liquid with the same composition as the original azeotrope, preventing further separation of the ethanol from water through distillation alone. To achieve a higher ethanol concentration, additional techniques such as molecular sieves or advanced distillation processes like pressure swing distillation or azeotropic distillation are required.