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Questions and Answers
What is the purpose of adding charcoal to the solution during the recrystallization process?
To remove colored impurities
Why is the solution filtered while hot during the recrystallization process?
To remove insoluble impurities
What is the purpose of cooling one flask slowly and placing the other flask in an ice bath during recrystallization?
To compare the appearance of the crystals
Why is it important to wash the crystals with a small amount of cold water?
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What should be done with the crystals after filtering and washing?
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Why is it recommended to cover the crystals with a filter paper if drying is done overnight?
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Recrystallization is the most common method of purifying solids involving the following steps: 1. Dissolve the solid (1.0 gram of low grade benzoic acid) in a 125 mL Erlenmeyer flask with a minimum amount of suitable solvent at its boiling point (in this case approximately 75 mL of boiling water).The solvent is added in small portions to avoid excess. 2. In case some colored impurities are present, add a pinch or more of ______. Heat the solution containing the charcoal to boiling with frequent stirring.
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As fast as possible, filter the solution while hot (to remove insoluble impurities) through fluted filter paper into an Erlenmeyer flask containing about 5 mL of water which is heated during the filtration process.(See to it that the funnel is hot to prevent crystallization on the funnel). 4. Divide the filtrate into 2 Erlenmeyer flask. Set aside one flask to cool slowly without disturbance to allow crystallization to take place. Place the other flask in an ice bath. Compare the appearance of the crystal in two ______.
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Combine the two solutions and filter the crystals. Wash with small amount of cold water to remove the adhering ______ liquor.
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Spread the paper with the ______ on a watch glass and allow to dry. (If drying is done overnight, cover the ______ with a filter paper and keep in your locker until the next laboratory period).
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Recrystallization is the most common method of purifying solids involving the following steps: 1. Dissolve the solid (1.0 gram of low grade benzoic acid) in a 125 mL Erlenmeyer flask with a minimum amount of suitable solvent at its boiling point (in this case approximately 75 mL of boiling water). The solvent is added in small portions to avoid excess. 2. In case some colored impurities are present, add a pinch or more of charcoal. Heat the solution containing the charcoal to boiling with frequent stirring. 3. As fast as possible, filter the solution while hot (to remove insoluble impurities) through fluted filter paper into an Erlenmeyer flask containing about 5 mL of water which is heated during the filtration process. (See to it that the funnel is hot to prevent crystallization on the funnel). 4. Divide the filtrate into 2 Erlenmeyer flask. Set aside one flask to cool slowly without disturbance to allow crystallization to take place. Place the other flask in an ice bath. Compare the appearance of the crystal in two flasks. 5. Combine the two solutions and filter the crystals. Wash with small amount of cold water to remove the adhering mother liquor. 6. Spread the paper with the crystals on a ______ glass and allow to dry. (If drying is done overnight, cover the crystals with a filter paper and keep in your locker until the next laboratory period).
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Recrystallization is the most common method of purifying solids involving the following steps: 1. Dissolve the solid (1.0 gram of low grade benzoic acid) in a 125 mL Erlenmeyer flask with a minimum amount of suitable solvent at its boiling point (in this case approximately 75 mL of boiling water). The solvent is added in small portions to avoid excess. 2. In case some colored impurities are present, add a pinch or more of charcoal. Heat the solution containing the charcoal to boiling with frequent stirring. 3. As fast as possible, filter the solution while hot (to remove insoluble impurities) through fluted filter paper into an Erlenmeyer flask containing about 5 mL of water which is heated during the filtration process. (See to it that the funnel is hot to prevent crystallization on the funnel). 4. Divide the filtrate into 2 Erlenmeyer flask. Set aside one flask to cool slowly without disturbance to allow crystallization to take place. Place the other flask in an ice bath. Compare the appearance of the crystal in two flasks. 5. Combine the two solutions and filter the crystals. Wash with small amount of cold water to remove the adhering mother liquor. 6. Spread the paper with the crystals on a watch glass and allow to dry. (If drying is done overnight, cover the crystals with a filter paper and keep in your locker until the next laboratory period). 7.
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