23. The following is commonly used in the organic laboratory for the removal of organic solvents under reduced pressure.
a. hot plate
b. hot plate and water bath
c. hot plate and sand bath
d. distillation
e. rotary evaporator
24. Why is it necessary to remove the stopper from a separatory funnel when the liquid is being drained through the stopcock?
a. to prevent the build-up of pressure
b. to prevent the formation of an emulsion
c. to prevent the formation of a vacuum that will prevent the liquid from draining
d. to prevent contamination of the layers from impurities in the air
e. to ensure proper separation of the layers
25. Which of the following organic solvents cannot be used for liquid-liquid extraction?
a. ethyl acetate
b. acetone
c. dichloromethane
d. pentane