PRE-LAB QUESTIONS 1. If a mixture is distilled rapidly, the separation of its compound is poorer than if the mixture is distilled slowly. Explain why this is true. 2. What effect would a decrease in atmospheric pressure have on the boiling point? What effect would an increase have? 3. Propose two properties (besides boiling point) that could be used to distinguish the unknown solvents.
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Distillation is a method used to separate components of a mixture based on differences in their boiling points. When a mixture is heated, the component with the lower boiling point vaporizes first, and this vapor can be condensed back into a liquid and collected Show more…
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When a pure liquid is heated, its temperature begins to rise. What happens when it reaches its boiling point? Explain. Water boils at 100°C while methanol boils at 64.7°C. Can you explain why? How is the separation of two liquids achieved using fractional distillation? How does it differ from simple distillation? Explain. In a 50:50 water:methanol mixture ready for distillation, a few boiling stones are added and the mixture is heated. Would you expect the mixture to start distilling at the boiling point of the lower or higher temperature material? Explain why or why not this would be observed.
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1. Explain why the observed boiling point changed over the course of the distillation for both the simple and fractional distillation. 2. Compare the purity of the fractions (first and last two mL) for the simple and fractional distillation. 3. From each distillation, what are the observed boiling points for each component in the mixture? What compounds would your data suggest are present in the mixture? 4. Explain why one component in your mixture has a higher boiling point by comparing their chemical structures. 5. Briefly explain the expected differences in a GC chromatogram for a 50:50 and 25:75 mixture of hexane (bp 68 °C) and toluene (bp 111 °C). Draw a simple picture to help you.
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