Question

. A student carried out a simple distillation on a compound known to boil at 124°C and reported an observed boiling point of 116°–117°C. Gas chromatographic analysis of the product showed that the compound was pure, and a calibration of the thermometer indicated that it was accurate. What procedural error might the student have made in setting up the distillation apparatus

Answer 1

Answer: The thermometer was wrongly positioned by the student.

Explanation:

It’s correctly observed that the student carried out proper distillation carefully to separate the components, the depressed boiling point observed cannot be caused by an impure distillate. The student incorrectly positioned the thermometer. The position of the bulb is critical for obtaining an accurate reading of the temperature of the vapour at the point where the vapour just reaches the side-arm that attaches to the condenser. Not low enough, and you will not be measuring the temperature of a vapour that is in equilibrium with the distilling mixture. That explains the depressed boiling range.