Term
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Definition
| Technique for the separation of a compound from a mixture |
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Term
| In what instances are extractions frequently employed? |
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Definition
| Extractions are employed fro the separation of an organic product from its rxn mixture and for the removal of any impurities |
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Term
| what does liquid-liquid extraction involve? |
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Definition
| Liquid-liquid extraction involves the distribution of solutes between two immiscible liqids. |
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Term
| what solvents are used in liquid-liquid extraction? |
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Definition
| water and a water-insoluble organic solvent (hexane,________,_____) |
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Term
| What governs the distribution of the solutes between the awueous phase and the organic phase? |
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Definition
| The distribution of the solutes between the aqueous phase and the organic phase is governed by their relative solubilities |
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Term
| In what phase is an inorganic salt more likely to be soluble? |
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Definition
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Term
| In what phase is an organic compound more likely to be soluble? |
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Definition
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Term
| Which layer is always lower layer? |
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Definition
| The one with greatest density |
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Term
| What circumstances will the aqueous and organic phases exchange places? |
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Definition
| When their relative densities change |
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Term
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Definition
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Term
| How large should the separatory funnel be? |
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Definition
| 2-4 times the combined volumes of the aqueous and organic phases |
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Term
| What precaution should be taken before adding a liquid to the separatory funnel? |
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Definition
| The stopcock should fit tightly and should be in the closed position |
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Term
| What seven steps constitute a typical liquid-liquid extraction? |
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Definition
1)Add the aqueous solution to the separatory funnel
2)Add the organic solvent to the separatory funnel
3)Insert a stopper; securely hold in position
4)Invery funnel; open stopcock to release pressure. Close stopcock then shake contents of funnel 4-5 times; open stopcock to release pressure. Carryout process 4-5 times.
5) Support separatory funnel in iron ring and allow layers to searate.
6) drain off bottom layer
7) Pour off top layer |
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Term
| what volume of organic solvent should be used |
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Definition
| 1/3 the volume of the aqueous phase |
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Term
| At what point in the extraction process should one discard solutions? |
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Definition
| Only when one knows for certain which flask contains the compound of interest |
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Term
| How can one ascertain whether a cetain layer is the organic phase or the aqueous phase? |
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Definition
| Add a drop of the mystery layer to 2mL of water. If the drop dissolves then it was taken from the aqueous phase. if the drop does not dissolve then it was taken from the organic phase. |
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Term
| Why must extraction solutions be at, or slightly below, room temperature? |
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Definition
| Because most organic solvents are quite volatile |
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Term
| what is a convenient method for cooling the aqueous phase prior to the addition of organic solvent? |
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Definition
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Term
| Why must one vent extraction mixtures? |
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Definition
| Since most organic solvents are quite volatile they evaporated easily- this generates pressure inside the separatory funnel |
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Term
| Pressure buildup in the separatory funnel is associated with the use of what extraction solvents? |
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Definition
| Volatile solvents such as diethey ether, hexane, dichloromethane |
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Term
| How can one "dry" an organic solution? |
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Definition
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Term
| For how long should the organic phase stand over the drying agent |
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Definition
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Term
| How is a dried organic phase separated from granular or chunky drying agents? |
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Definition
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Term
| what methods may be employed for the removal of the organic solvent from the compounds of interest? |
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Definition
1) Evaporation (For small volumes)
2) Distillation (For larger volumes) |
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