Two miscible liquids, A and B, are present in a mixture. The boiling point of A is 60 °C and the boiling point of B is 90 °C. Suggest a method to separate them. Also, draw a labelled diagram of the method suggested.
The method suggested to separate the mixture of two miscible liquids, A and B, is distillation. This method is appropriate because the boiling point of liquid A is 60 °C and liquid B is 90 °C, resulting in a difference of 30 °C. Distillation allows the separation of liquids that differ in boiling point by at least about 25 °C.
In this process, the mixture is heated in a distillation flask. Upon heating, the liquid with the lower boiling point, which is liquid A, vaporises first when the temperature reaches 60 °C. The vapours of this lower-boiling liquid are then directed into a condenser.
Inside the condenser, the vapours are cooled, typically by circulating water or air, and they condense back into a pure liquid. This pure liquid A is collected in a separate vessel. Meanwhile, liquid B, which has a higher boiling point of 90 °C, remains in the distillation flask.
Labelled Diagram of Distillation: [Diagram shows a Distillation Flask heated by a burner, containing the mixture. A Condenser is attached to the flask (with cold water inlet and outlet), where vapours cool and condense. The pure liquid A drips into a Separate Vessel (receiver) placed at the end.]
Explanation
The textbook context specifies that distillation is used to separate a homogeneous mixture of two miscible liquids that differ in boiling point by at least about 25 °C. Since the difference between liquid A (60 °C) and liquid B (90 °C) is 30 °C, distillation is the correct method. The process involves vaporising the lower-boiling liquid, passing the vapours through a condenser to cool them back into a liquid, and collecting it in a separate vessel while the other liquid remains in the distillation flask.
Solution Steps
Step 1: Calculate the difference in boiling points (90 °C - 60 °C = 30 °C).
Step 2: Select the separation method. Since the difference is greater than 25 °C, distillation is the suitable method.
Step 3: Describe the process: Heat the mixture in a distillation flask. Liquid A vaporises first at 60 °C.
Step 4: The vapours pass into a condenser, are cooled by circulating water/air, and condense into pure liquid A, which is collected in a separate vessel. Liquid B remains in the flask.
Step 5: Draw/Describe the labelled diagram including the Distillation Flask, Condenser, and Separate Vessel.