?? If during an extraction you are unsure as to which layer is which, what simpl
ID: 789756 • Letter: #
Question
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If during an extraction you are unsure as to which layer is which, what simple maneuver would you do? You have 10 grams of a compound. Eight grams is soluble in 100 ml of boiling solvent and 3 grams is soluble in 100 ml of cold solvent. What is the minimum amount of solvent you will need to dissolve your compound? What is the maximum yield of crystals you would expect? Show your calculations. You perform recrystallization on 60 mg of crude solid material and recover 45 mg of pure solid. What is the percent recovery? If further concentration of the mother liquor offers an addition 8 mg, what is the total percent recovery?Explanation / Answer
6)The top layer will be lighter so it might be raffinate
The bottom layer will be heavier ,so it might be extract
The above answers hold if the density of solute is higher than density of solvent.
To differentiate two layers we have to find concentration of solute in the layers
7) Mininum solvent will be when the compound dissolves in boiling solvent
for 10 gms of compound, boiling solvent required = (10/8)*100 = 125 ml
Mininum solvent = 125 ml
When we cool that solvent,
amount compound in dissolved form in 125 ml cold solvent = (3/100)*125 = 3.75 gm
Weight of crystals of compound formed = 10-3.75 = 6.25 gm
Maximum yield = (6.25/10)*100 = 62.5 %
8)
percentage recovery before concentrating mother liquor = (45/60)*100 = 75%
total percent recovery after concentrating mother liquor =[(45+8)/60]*100 = 88.33 %
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