Organic Chemistry Laboratory I (X36.1A)PRE-LAB QUIZ for EXPERIMENT 6Name ___________________________For each question write the letter of the correct answer in the column on the right :1. Recrystallization is a laboratory procedure that is usually performed in order toA) increase the yield of the product of a reactionB) separate enantiomersC) determine whether a compound is polar or non-polarD) increase the purity of the product of a reactionE) lower the melting point of the product of a reaction2. Why is benzene (C6H6 boiling pt. 78°C) not used as a recrystallization solvent?A) because it is non-polarB) because it is an aromatic compoundC) because its boiling point is too lowD) because it forms explosive peroxidesE) because it is toxic and an environmental hazard3. Why is pentane (C5H12 boiling pt. 36°C) not used as a recrystallization solvent?A) because it is non-polarB) because it is an aromatic compoundC) because its boiling point is too lowD) because it forms explosive peroxidesE) because it is toxic and an environmental hazard4. The most important reason for adding a boiling stick to a liquid before heating it isA) to prevent bumping (overheating) of the liquidB) to stir the liquid while it is being heatedC) to prevent the liquid from boilingD) to lower the boiling point of the liquidE) to absorb impurities that are in the liquid on the surface of the wood5. Norit® is the name of a company and of its main product which isA) boiling sticksB) activated charcoalC) a solvent used for recrystallizationD) weighing paperE) mother liquor 6. When you have a hot solution from which crystallization will occur you shouldA) allow it to cool slowly and undisturbedB) immediately cool it in an ice bath so that crystals will form rapidlyC) stir the solution vigorously with a stirring rod or boiling stick while it is coolingD) place the solution under vacuum so that solvent will evaporate and crystals will formE) add boiling chips to prevent “bumping” of the hot liquid7. If the yield of crystals is small a second crop of crystals can be obtained byA) adding more solventB) heating the solution to evaporate some of the solvent and then coolingC) adding sand from the sand bathD) adding activated charcoalE) passing the solution through a Pasteur pipette containing glass-fiber filter paper8. In a recrystallization procedure the liquid that remains at the end of theprocedure after the purified crystals have been removed from it is called theA) cosolventB) distillateC) rinseD) mother liquorE) water bath9. In the decolorization of brown sugar (Experiment 6 Part II) activated charcoal isremoved byA) vacuum filtrationB) distillationC) extraction with an acidic solventD) the glass-fiber Pasteur pipette methodE) centrifugation10. A boiling stick must be added to a solution before the solution is heated becauseif a boiling stick is added to a hot solutionA) the stick may dissolve in the solutionB) the stick may cause crystallization to occur prematurelyC) many bubbles may form quickly and the solution may froth and “bump”D) the stick will absorb the substance that is being recrystallizedE) the stick will prevent crystallization from taking place
