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exp 4 chem 235

Terms in this set (15)

the process of a liquid or solid entering the bulk of another material
Absorption
phenomena of elevation or depression and of adhesion and cohesion of a liquid observed in a thin tube that is placed in a liquid. This is due to surface tension.
Capillary Action
a process where the heated vapors of a liquid enter a condenser and are cooled back to a liquid state then flow back to the original boiling solution. A 'good' reflux rate is estimated as 1 drop of liquid/second off the end of the condenser
Reflux
an adjustable resistance for regulating electric current; used to regulate the temperature of the thermowells since they have no regulating dials.
Rheostat
"the making of soap" the alkaline hydrolysis of a fat
Saponification
"streaking" of a substance on a TLC plate. Occurs if too much of a material is spotted on the plate OR if the material is very polar and is more attracted to the plate than to the developing solvent. This latter case can be minimized by adding a few drops of acetic acid to the developing solvent to increase its polarity.
Streaking
the more strongly a solute interacts with the stationary phase, the ________ it will migrate through the system.
slower
starting line
baseline
end line
solvent front
the _____ of liquid-solid absorption chromatography known as thin-layer chromatography is called because the solid absorbent is spread in a thin layer on an inert suuport material. The combination of these items is called a TLC plate. The solute is dissolved into the mobile phase and loaded at the bottom of the plate. The TLC plate is developed and the mobile phase is allowed evaporate. These solute spots are then visualized using a variety of methods and the ratio-to-front (Rf) is measured.
form
polar functional group are less absorbed and travel ___ and stay close to the solvent front
far
polar functional group are more strongly absorbed and do not travel far and stay _______ to the baseline
close
distance travelled by solute spot / distance travelled by solvent front
Rf
Assuming a silica-based stationary phase was used, arrange the following compounds containing different functional groups in terms of increasing distance travelled on a TLC, assuming polarity of the functional group is the only difference between the three compounds: carboxylic acid, ester, alkyl halide.
Carboxylic acid, Ester, Alky halide
Why is streaking undesirable for TLC analysis?
irregular shapes will make it more difficult to measure the Rf values
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