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14 Cards in this Set

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Why is fluted filter paper more efficient than filter paper folded into a smooth cone for gravity filtrations?
Regular filter paper is inefficient, since very little of the paper is exposed. The idea is to have flute or corrugated paper to increase the surface area that is in contact with the filtrate.
Why should you use a stemless funnel for hot gravity filtrations during a recrystallization?
Stemless funnels should be used, because with long-stemmed funnels, the crystals come out in the stem as the solution cools, blocking up the funnel.
Which of the following should you not heat on a hot plate: diethyl ether, ethanol, water, ethyl acetate
All besides water
Why is slow cooling important to the purification?
Slow cooling is important, because slower cooling processes yield purer crystals (impurities remain in solution)
Knowing that like dissolves like, are the compounds in this lab going to be more soluble in ethanol or water?
N-Acetylanthranilic Acid will dissolve better in water; 1,2-Diaminocyclohexane will dissolve better in ethanol
How would the yield/melting point be effected if too much solvent was used?
Crystals remain in solution when cooled ~ yield decreases
How would the yield/melting point be effected if too little solvent was used?
Not all of your crystals will dissolve in the hot solvent, andthey’ll retain some impurities ~ melting point decreases; yield might also decrease as they get filtered out during gravity filtration.
How would the yield/melting point be effected if the hot solution was filtered by suction?
Your compound would still be dissolved in the hot, so yield would decrease
How would yield/melting point be effected if the crystals (after suction filtration) were washed with warm solvent?
They would redissolve ~ yield less
How would the yield/melting point be effected if the crystals were not washed at all?
Further impurities would remain ~ melting point would decrease; yield might also increase.
How would the yield/melting point be effected if there was inadequate suction during vacuum filtration?
The liquid would not all be pulled through, so the soluble impurities would remain, so as a whole melting point would be less.
What 5 things you look for in a perfect recrystallization solvent?
1. Dissolves solid while hot
2. Does not dissolve solvent while cold
3. Cold solvent keeps impurities dissolved in it indefinitely
4. “Like dissolves like”
5. Solid does not dissolve at room temperature
How is melting point effected in impure compounds?
Melting point is lower.
How would you dispose of a solution of your N-acetylanthranilic acid product in a methanol/water mixture?
In a blue bucket for chemical waste