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