A student is trying to perform a single solvent recrystallization of compound X using methanol. He observed that compound X is insoluble in methanol at room temperature and also insoluble at boiling temperature. Is methanol a good recrystallization solvent? A. Yes, you want to only dissolve the impurities and the sample should remain undissolved. B. No, you need a solvent which fully dissolves the sample only at room temperature so that it can crystallize in the ice bath. C. No, you need a solvent which dissolves the sample only at boiling temperature for selective crystallization upon cooling. D. Yes, you don't want the solvent to fully dissolve the sample at both temperatures so that it will crystallize in the cooling step. A student obtained a supersaturated solution in the recrystallization experiment. Which of the following methods should he/she perform to induce crystal growth? (Can select more than 1) A. Add a crystal of pure acetylsalicylic acid B. Place the solution in an ice bath to lower the solubility of the solute C. Boil off the excess solvent D. Scratch the inner walls and bottom of the container E. Add excess solvent to dilute the solution Which of the following is/are correct regarding mixed-solvent recrystallization? (can choose more than 1) A. None of the choices B. It uses two immiscible solvents. C. Solute should be insoluble in both solvents D. Solvents used should dissolve the solute at all temperatures E. Solvents used should chemically react with the solute
A student is trying to perform a single solvent recrystallization of compound X using methanol. He observed that compound X is insoluble in methanol at room temperature and also insoluble at boiling temperature. Is methanol a good recrystallization solvent? A. Yes, you want to only dissolve the impurities and the sample should remain undissolved. B. No, you need a solvent which fully dissolves the sample only at room temperature so that it can crystallize in the ice bath. C. No, you need a solvent which dissolves the sample only at boiling temperature for selective crystallization upon cooling. D. Yes, you don't want the solvent to fully dissolve the sample at both temperatures so that it will crystallize in the cooling step. A student obtained a supersaturated solution in the recrystallization experiment. Which of the following methods should he/she perform to induce crystal growth? (Can select more than 1) A. Add a crystal of pure acetylsalicylic acid B. Place the solution in an ice bath to lower the solubility of the solute C. Boil off the excess solvent D. Scratch the inner walls and bottom of the container E. Add excess solvent to dilute the solution Which of the following is/are correct regarding mixed-solvent recrystallization? (can choose more than 1) A. None of the choices B. It uses two immiscible solvents. C. Solute should be insoluble in both solvents D. Solvents used should dissolve the solute at all temperatures E. Solvents used should chemically react with the solute
Chapter80: Crystallization: Purification Of Solids
Section: Chapter Questions
Problem 4P
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Transcribed Image Text:A student is trying to perform a single solvent recrystallization of compound X using methanol.
He observed that compound X is insoluble in methanol at room temperature and also insoluble at
boiling temperature. Is methanol a good recrystallization solvent?
A. Yes, you want to only dissolve the impurities and the sample should remain undissolved.
B. No, you need a solvent which fully dissolves the sample only at room temperature so that
it can crystallize in the ice bath.
C. No, you need a solvent which dissolves the sample only at boiling temperature for
selective crystallization upon cooling.
D. Yes, you don't want the solvent to fully dissolve the sample at both temperatures so that it
will crystallize in the cooling step.
A student obtained a supersaturated solution in the recrystallization experiment. Which of the
following methods should he/she perform to induce crystal growth? (Can select more than 1)
A. Add a crystal of pure acetylsalicylic acid
B. Place the solution in an ice bath to lower the solubility of the solute
C. Boil off the excess solvent
D. Scratch the inner walls and bottom of the container
E. Add excess solvent to dilute the solution
Which of the following is/are correct regarding mixed-solvent recrystallization? (can choose
more than 1)
A. None of the choices
B. It uses two immiscible solvents.
C. Solute should be insoluble in both solvents
D. Solvents used should dissolve the solute at all temperatures
E. Solvents used should chemically react with the solute
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