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38 Cards in this Set

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When do things distill at a constant temperature?
When they are pure or when there is an azeotrope
When do you use simple distillation?
BP is less than 150
25 degree difference between the 2 liquids (or more)
When do you use fractional distillation?
less than a 25 degree difference between the 2 liquids
How do you calculate the hold up?
The amount you started w/ - the amount you end up with
solute
an compound dissolved in a compound compound and present in a lesser amount.
solvent
The compound which is present in the excess.
It is capable of dissolving a solute but not reacting with it.
miscible
Two or more compounds, which dissolve in one
another to form a homogenous solution are said to be miscible.
tituration
Repeated washing of a solid with a solvent.
filtrate
The material that passes through the filter and remains in the receiving flask. It is sometimes referred to as the mother liquor.
What do the h-bonds in water make it easy to dissolve?
Ionic solids (NaCl) and polar compounds like alcohols
What kinds of things does toluene dissolve?
aromatic , b/c it is aromatic w/ its benzene ring
What kinds of things does hexane dissolve? why?
hydrophobic, b/c it is an aliphatic hydrocarbon
What is necessary for a solvent in recrystallization?
Dissolves a temps higher than room temp
What does the boiling chip do?
keeps things from boiling out
What is a good decolorizing agent?
charcoal
What happens to the melting point if the sample is not dry
it is low/broad
What happens to the melting point if their is a soluble impurity in the compound?
it is low/broad
When do you gravity filter?
crystallization with impurities
When do you vaccumm filter?
cyrstallization w/ out impurities
When dichlorothemane (methylene chloride) is the solvent, it it on top or below water?
it is on the botom
When ether is the solvent, is it on top or below the water?
it is on the top
Why do you was the test tube w/ ether in extraction?
to get a more pure product
What is a chaser solvent?
helps remove the compund from the packing material by heating it up, allowing more recovery to be possible
cyclohexane + Br2 has what stereochemistry?
anti addition of Br's
cyclohexene + KMnO4 in a basic solution has what stereochemistry?
syn addition of OH's
major product of the dehydration of 2-methylcyclohexanol. Draw the mechanism
1-methylchyclohexen
what should be the limiting reagent in the adol rxn if you want to make dibenzalacetone?
acetone
What do you make w/ excess acetone in the adol rxn?
benzalacetone
What error do you see if the thermometer isn't below the sider arm in distillation?
the thermometer readis would be low, b/c the vapor wouldn't reach the bulb as it was distilled
As atmospheric pressure increases, what happens to the boling points?
the boiling points would increase
How do you find the composition of a vapor from partial pressures?
find the total pressure, and divide each of the partial pressures by it
If a compound has the highest partial pressure, will it have the highest or lowest boiling point?
it will have the lowest boiling point (lots of pressure makes it want to escape into the atm)
If after removing bicarbbonate from an aqueous layer that is supposed to be acidic, what is likely to have occured inf the layer is neutral?
there is still some bicarb in the tube
In crystallization, why don't we heat the test tube if the solid has disolved at rome temperature?
b/c this means the solvent is bad, b/c the solute is not recoverable
why remove the boiling stick before cooling in crystallization?
so that the impurities are not cooled into the crystals
What would happen if the solvent boiled too long during crystallization?
The Wi/mL measurement would be too small b/c some of the solvent would evaporate out.
Why does adding water to a hot filtrate cause it to cloud during crystallization?
b/c the solution is becoming saturated, the 1st step to forming crystals
why wash w/ hot ethanol when funniling in crystallization?
It is best at disolving, therefore more crystalls are recovered