Organic Chemistry Lab I (CHEM 237) Experiment 2: Recrystallization - Flashcards

question

The solubility of acetanilide is 18.5 g in 100 mL of methanol at 0 °C, and 59.2 g in 100 mL of methanol at 60 °C. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from methanol?

answer

68.75 %

question

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 151 mg. The mass after recrystallization was 119 mg. Calculate the percent recovery from recrystallization.

answer

78.8 %

question

Draw the structure of acetanilide

answer

Acetanilide, c8h9nO, is the product of the reaction of aniline and ethanoic acid (acetic acid). Acetanilide is easily recrystallized using water.

question

List the procedural steps, from start to finish, that are required in the recrystallization of acetanilide.

answer

The mixture was placed in a warm flask, and dissolved in the minimum amount of hot water. The solution was filtered while hot through a pre-warmed filter. The filter was washed with hot water, and the filtrate was collected and cooled to force precipitation. The solid precipitate was filtered cold, and dried on the filter.

question

Acetanilide was recrystallized from a minimum amount of hot water, then collected using vacuum filtration. Identify where the waste generated by this process should go. Drag and drop the chemical wastes generated in this reaction into the appropriate container.

answer

The filtrate, containing mostly water, should go to the Dissolved Acetanilide in Water from Recrystallization waste. The acetone rinse should go in the Wash Acetone waste container. The filter paper should be placed in the Dissolved Acetanilide in Water from Recrystallization waste container. The melting point capillary should go to the Glass waste container.

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question

During the recrystallization of an impure solid sample of acetanilide, the sample is dissolved in hot water then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. Which of the following actions will increase the percent recovery of the acetanide solute?

answer

After the first filtration, Place the solution in an ice-water bath for about 10 minutes.

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question

During the recrystallization of an impure solid sample, the sample is dissolved in hot water then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. Which procedure should a student NOT do if they observe an oil forming as the solution cools?

answer

Add a small amount of ice-cold water.

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Organic Chemistry Lab I (CHEM 237) Experiment 2: Recrystallization – Flashcards

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