1. A student carried out a simple distillation on a compound known to boil at 12

Question

1. A student carried out a simple distillation on a compound known to boil at 1240C and reported an observed boiling point of 1160-1170C. Gas chromatographic assay of the product showed the compound was pure, and a thermometer calibration indicated that it was accurate. What procedural error might the student have made in setting up the distillation apparatus?

2. If the resolution (base-line separation) of two compounds with a GC assay is mediocre but shows some partial peak resolution, what are two adjustments that can be made in the instrument operating parameters to improve the resolution without changing the column or instruments?  

3. Why is it best to connect water to a condenser so that it flows in at the bottom and out at the top?  

4. How can you judge whether the amount of heat applied (from a Variac setting) to a reflux apparatus is sufficient but not too much?  

Explanation / Answer

Ans 1

Pure compound has been distilled.

Observed boiling point is less than the original boiling point

The student has done is incorrectly positioned the thermometer.

The bulb position is most important to obtain the accurate reading of the vapor temperature.

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