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Cards In This Set
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What is liquid liquid extraction?
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A widely used method to separate mixtures (mixture can be solid or liquids)
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What is liquid liquid extraction based upon?
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It is based on the differences in solubility of the components in two immiscible solvents
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When choosing the solvents for liquid-liquid extractions, what characteristics must they have?
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1) First solvent would preferably completely dissolve both compounds in the mixture
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When choosing the solvents for liquid-liquid extractions, what characteristics must they have?
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2) Second solvent selected must be immiscible with the first solvent
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When choosing the solvents for liquid-liquid extractions, what characteristics must they have?
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3) Second solvent should preferentially dissolve only one component of the original mixture
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How does liquid liquid extraction work?
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Mixture is dissolved or suspended in the first solvent and then this solution is introduced to the second solvent.
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How does liquid liquid extraction work?
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By shaking the solvent together in an apparatus called a separatory funnel, one component of the mixture will be transferred into the second solvent
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How does liquid liquid extraction work?
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This would leave the other component in the first solvent.
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How does liquid liquid extraction work?
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Final separation of two solvents is accomplished using separatory funnel - followed by evaporation of solvents, produces the separated components
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But if all we did was the following procedure, we would not have totally separated the two compounds. How do we increase our success?
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Compound that we are extracting with 2nd solvent, even though is more soluble in 2nd solvent than 1st but can still dissolve in 1st solvent
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What is the extent of the compound dissolve in the less soluble 1st solvent governed by?
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The partition coefficient of extraction. This forces us to repeat the extraction step many times
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What happens when we repeat the extracting step many times?
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We add a fresh portion of the solvent to separatory funnel containing original solution of mixture, to ensure that we get best possible separation
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Draw the diagram for successive extractions
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Now compare to the one in the manual
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Solutions should never occupy more than what amount of volume of the separatory funnel?
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Solutions should never occupy more than 2/3 of the volume of the funnel or else proper mixture will be difficult
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What do we rest the stopper of the funnel before use?
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On a clean watch glass
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