For her majors chemistry lab, Freja performs a recrystallization of ibuprofen th
ID: 553831 • Letter: F
Question
For her majors chemistry lab, Freja performs a recrystallization of ibuprofen that is significantly impure. After dissolving the sample in minimal boiling acetone, Freja removes the flask containing the dissolved ibuprofen from the hot plate. Being impatient, Freja decides tò skip the step-in which the flask is cooled to room temperature. Instead, she sticks the flask of dissolved ibuprofen immediately into the freezer. To her gratification, crystals form almost immediately. Freja filters them, dries them, weighs them, and obtains a percent recovery of 99%. What is likely true about her recovered product? O It is pure, because her percent recovery is a nearly perfect 100%. O It is impure, and its melting point will be low and broad relative to authentic ibuprofen It is impure, and its melting point will be low and narrow relative to authentic en. o It is impure, and its melting point will be high and narrow relative to authentic ibuprofen. It is impure, and its melting point will be high and broad relative to authentic ibuprofenExplanation / Answer
1) Recrystallization of ibuprofen
The sample obtained after recrystallization would be,
- it is impure, and its melting point will be low and broad relative to authentic ibuprofen
Impurities lower the melting point. Since the solution was cooled immediately, impurities have also recrystallized along with ibuprofen.
2) Snoop dog performs recrystallization of NBS.
He adds impure sample to boiling water. He does not get any crystals because,
- Snoop Dog added too much water
The proper way is to add small amounts of water to the impure sample, heat it to see If it dissolves, continue doing this until all of the sample dissolves and then cool the sample to room temperature to get pure crystals.
3) La fonda performed recrystallization of chlorobenzoic acid.
The obtained compound could be,
- Impure 2-isomer
- Impure 3-isomer
Here again impurities have lowered the melting point of pure compounds.
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