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Which one is not used as extraction apparatus for solvents that are lighter or heavier than water?
C) Addition Funnel
Correct Answer: An addition funnel is not needed in this extraction process; addition funnels are designed for slowly adding a reagent to a reaction vessel.
D) Extractor Body
Hydrodistillation analysis of essential oils sourced from biomass is generally done by collecting the distillate in a tube and returning the excess water to the boiling flask. This is accomplished by using an apparatus named after its inventor. What is the name of this apparatus?
Correct Answer: J. F. Clevenger first described the apparatus in 1928. The apparatus is connected to a round bottom flask containing the biomass and water on one end, and a condenser on the other. The rather specialized use of this apparatus has allowed it to remain in relative obscurity.
Which of the following products would be best for separating a mixture based on differences in the constituents’ boiling points?
C) Buchner Funnel
B) Chromatography Column
A) Distillation Column
Correct Answer: Distillation separates volatile liquids based on differences in their boiling points. Büchner funnels are utilized when the mixture can be separated by particle size. Chromatography columns separate mixtures by means of passing the mixture through a medium in which components move at different rates.
D) All of the above
Which of the following is a way to increase the distillate purity in a fractional distillation process?
C) Add a second condenser beyond the receiving flask.
B) Operate under lower pressure.
A) Increase the temperature of the heat source.
Correct Answer: Increasing the surface area of a column increases the vapor’s interaction with the column and slows the vapor’s movement up the columm. The result is increased retention time, which can improve distillate purity.
D) Increase the surface area of the column.
Which of the following is not a type of column for fractional distillation?
C) Vigreaux column
B) Michel-Miller column
A) Hempel column
D) Snyder column
Correct Answer: The Michel-Miller column is used for column chromatography, not distillations.
Which of the condensers are not ideal for refluxing?
C) Coil condenser (coolant flows through a central coil; opposite of Graham)
B) Allihn condenser (coolant flows outside a bulb-shaped path)
A) Graham condenser (coolant flows outside a central coil)
D) Liebig condenser (coolant flows outside a straight walled path)
Correct Answer: The Graham condenser is not ideal for refluxing because it is prone to flooding and clogging when condensed vapor flows down the coil, blocking the rising solvent vapor. However, it is effective at cooling liquids that are moving in a continuous direction.
What is the safest and most accurate method to heat a round-bottom flask?
C) Over an open flame
B) Heated oil bath or sand bath
A) Heating mantle combined with a temperature controller
D) Directly on a hot plate
Correct Answer: Heating a round-bottom flask with oil and sand can be messy and slow. Using an open flame is uneven and can pose fire safety hazards. Placing the flask directly on the hot plate can cause hot spots, which can damage the integrity of the glass. By contrast, a heating mantle combine with a temperature controller can provide feedback via a thermouple to accurately and safely heat a flask.
What glass joint types are recommended for vacuum applications?
C) Ace Thred + Bushing system
B) O-ring Spherical Joint
A) Standard Taper Joints
Correct Answer: All the glass joint types listed can provide an effective seal under vacuum. Standard taper joints and spherical joints may need vacuum grease to perform to a high standard, but both work quite well in a vacuum environment. The Ace-Thred system is perfect for bushing in tubing, thermometers, or other cylindrical items into flasks or reactors. As long as the O-ring is cared for and replaced when worn, very low vacuum can be achieved.
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