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A. Bulb of Thermometer placed at Outlet of Condenser
Purpose: To measure the temperature of the vapour entering the condenser so as to identify the distillate
As the solvent (liquid) has a lower boiling point as compared to the solute (soluble solid), the solvent will boil first and become a gas (vapour), before condensing in the condenser to be collected as a distillate
Boiling takes place at a constant temperature at the boiling point of the solvent, thus allowing us to identify the identity of the solvent (distillate)
The temperature is too low for the solute to boil. Hence, we can be sure that the distillate being collected is the solvent and not the solute.
E.g., boiling point of water is 100°C, while boiling point of sodium chloride is 1465°C.
At 100°C, we can be sure that the vapour entering the condenser is water and not sodium chloride.
B. Boiling chips are added to the solution in the distillation flask
Purpose: To ensure smooth boiling
Boiling chips are porous stones of high surface area that act as nucleation sites for formation of solvent bubbles, thus allowing the solution to boil more calmly.
C. Condenser is filled with cold water from the bottom which leaves from the top
Purpose: Ensure that the condenser is completed filled with cold running water, such that the part of condenser near the collection of distillate is cool.
Filling the condenser from the top will cause the cold running water to flow down the condenser quickly due to gravity.
If the condenser is not filled, it prevents the vapour from being cooled efficiently. Not all the vapour will condense, thus resulting in a lower yield of distillate.
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