Question

1. Explain how a fractionating column increases the separation of two liquids.

2. What is an azeotrope? Do you think the mixture used in the lab is an example of an azeotrope? Explain.

3. Explain how the boiling point of a liquid is affected by the addition of a non-volatile solute (hint: it is a colligative property). Is the temperature above such solution lower, higher or the same as the pure liquid? Explain why.

4. You were asked to record the distillation temperature for your first fraction when you observed the first drop of distillate. Why is that different from recording the temperature when the solution first starts boiling?

5. What would happen if you set up your distillation with a loose joint such as the one pictured below?

Answer 1

1. The fractionating column consists of glass beads in the column on which the liquid condense , re evaporate and condense again.

Thus, making it easy for liquids to separate.

2. Azeotropes are constant boiling point mixtures and their composition donot get changed by the distillation.

Example- Ethanol in water

Nitric acid in water

3. When we add non volatile solute to the solvent it's boiling point tends to decrease.

This is relative lowering of vapour pressure and the temperature may increase to a value more than the vapor pressure of pure solvent to achieve pressure that becomes equal to atmospheric pressure.

4.