Kaplan Organic Chemistry: Chapter 12 Separations and Purifications

Question 1

a simple distillation can be used for liquids that boil below ___ and have at least a ___ difference in boiling point

Answer 1

a simple distillation can be used for liquids that boil below 150 and have at least a 25 difference in boiling point

Question 2

a vaccuum distillation is used to distill a liquid with a BP above ___

Answer 2

150

Question 3

purpose of vacuum in a vacuum distillation

Answer 3

the vacuum lowers the pressure, and decreases the temp needed for the liquid to reach a boil.

Question 4

what type of distillation is good for compounds that have BPs less than 25 degrees apart?

Answer 4

fractional distillation.

Question 5

the technique where beads in a column are coated with charged substances so that they attract compounds that have an opposite charge is an example of ___ chromatography

Answer 5

ion exchange chromatography

Question 6

in anion-exchange chromatography, what elutes first?

Answer 6

you exchange an anion for a cation, which elutes first. the column is positively charged to retain the anion

Question 7

what type of molecule will come off the “gas chromatograph” first?

Answer 7

the one with the lower boiling point.

The lower the boiling point is, the higher the vapor pressure of the compound the more time the compound will spend in the gas phase and will “elute” first

Question 8

in high performance liquid chromatography, the stationary phase is ___, and the mobile phase is ___. what about in reverse phase HPLC?

Answer 8

in high performance liquid chromatography, the stationary phase isPOLAR, and the mobile phase is NONPOLAR

Reverse: nonpolar STATIONARY, POLAR MOBILE.