UOP CHEM 121 LAB FINAL EXAM QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED GRADED A+
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Course
CHEM 121
Institution
CHEM 121
UOP CHEM 121 LAB FINAL EXAM QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED GRADED A+
The spot must be applied to the TLC plate above the level of development solvent.
False
In the extraction of capsaicin lab 2 solvents are used (9:1 hexane-ethyl acetate mixture) and (1:1 hexane-ethyl acetate mixtu...
UOP CHEM 121 LAB FINAL EXAM QUESTIONS WITH COMPLETE
SOLUTIONS VERIFIED GRADED A+
The spot must be applied to the TLC plate above the level of development
solvent.
False
In the extraction of capsaicin lab 2 solvents are used (9:1 hexane-ethyl acetate
mixture) and (1:1 hexane-ethyl acetate mixture). Which solvent mixture will cause
the spot to have a smaller Rf value?
9:1 hexane-ethyl acetate mixture
Rf value can be calculated with what information?
distance spot travels and distance solvent travels
Why is the filter paper is an essential part of the TLC set up?
saturation of the container atmosphere
Describe all the necessary glassware and reagents for a TLC development
chamber and explain the purpose of each part. What are the components of the
TLC plate?
When preparing your TLC plate, you have both ethyl acetate and hexane as
solvent options. Using hexane, the compound stays at the originally spotted
location. Using ethyl acetate, the compound runs to the top of the solvent. What
are the Rf values of both results? How should you proceed and why?
Hexane will produce Rf of 0, ethyl acetate will produce Rf of 1
Methods to visualize TLC plate
UV (aromatics and conjugated systems), Iodine Chamber (aromatics), Permanganate
(Alkenes, Alkynes, Aldehydes or alcohols)
The initial process resulting in the formation of a crystal in which there is a small
arrangement of in a pattern characteristic of a solid is
nucleation
general steps of crystallization
, 1. Choose a solvent that dissolves when hot
2. Dissolve the solute at boiling point
3. Decolorize the solution with activated charcoal
4. Filter suspended solids with hot gravity filtration
5. Recrystallize the solute by cooling
6. Collect and wash crystals with suction filtration
7. Dry Crystals
Concepts of Recrystallization
1. Exclusion: impurities are excluded
2. Nucleation: seed crystal is super saturated with solute
3. Saturation level: as solvent cools, the solution becomes saturated with respect to
solute
4. Solubility: solute must be soluble in hot solvent not cold
Impurities in hot solvent are filtered out via gravity filtration
True
Crystallization
an isolation technique of crude material when it is no longer soluble
Recrystallization
is a purification technique of crude material
Simple Distillation
- Liquids that boil below 150 C and have at least 25C difference in boiling temperature.
- Consists of a distilling flask (containing combined solution), distillation column
( thermometer, condenser, and receiving flask to collect the distillate.
Fractional distillation
fractionating column is useful for successive condensations and distillations which will
be better at separating liquids with boiling points that exceed a difference of 75 degrees
Celsius
boiling point
the point at which the vapor pressure equals the atmospheric pressure
theoretical plate
represents one vaporization/condensation cycle
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