CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

General Chemistry 101/102General Chemistry 101/102Laboratory ManualLaboratory Manual

University of North Carolina at WilmingtonUniversity of North Carolina at Wilmington

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

• PurposePurpose Use the technique of vacuum filtration to separate Use the technique of vacuum filtration to separate

a a heterogeneous mixtureheterogeneous mixture into its components. into its components. Use the technique of fractional crystallization to Use the technique of fractional crystallization to

separate a separate a homogeneous mixturehomogeneous mixture into its into its components.components.

• Safety ConsiderationsSafety Considerations Exercise care not to burn yourself on hot Exercise care not to burn yourself on hot

ringstands, rings, and beakers.ringstands, rings, and beakers. Dispose of all waste materials in the appropriately Dispose of all waste materials in the appropriately

labeled containers in the hood.labeled containers in the hood.

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

• ProcedureProcedure Add about 25 g of one of the unknown mixtures to Add about 25 g of one of the unknown mixtures to

a pre-weighed 250 mL beaker. Weigh the beaker a pre-weighed 250 mL beaker. Weigh the beaker and mixture to determine the mass of the mixture.and mixture to determine the mass of the mixture.

Add 60 mL of DI water to the beaker and heat the Add 60 mL of DI water to the beaker and heat the mixture to 85 ºC (mixture to 85 ºC (do not allow it to boildo not allow it to boil) while ) while stirring. Keep the mixture near 85 ºC for 5 stirring. Keep the mixture near 85 ºC for 5 minutes with stirring.minutes with stirring.

While the mixture is While the mixture is heating, setup a vacuum heating, setup a vacuum filtration system.filtration system.

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

• ProcedureProcedure Place a piece of filter paper in Place a piece of filter paper in

the Büchner funnel with the the Büchner funnel with the curved edge down. Moisten curved edge down. Moisten the paper with a small amount the paper with a small amount of DI water.of DI water.

curved edge down

Turn on the water to the Turn on the water to the aspirator and pour the hot aspirator and pour the hot solution into the funnel. Use solution into the funnel. Use the rubber policeman to the rubber policeman to transfer all solid material to transfer all solid material to the funnel.the funnel.

sand

filtrate

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

Pour the filtrate into a clean 250 mL beaker and Pour the filtrate into a clean 250 mL beaker and save it for the recrystallization.save it for the recrystallization.

• ProcedureProcedure

While applying suction, wash the While applying suction, wash the sand twice with 25 mL portions of DI sand twice with 25 mL portions of DI water. Continue to apply suction for water. Continue to apply suction for 3-4 minutes to help dry the sand. 3-4 minutes to help dry the sand. Discard the wash water that collects Discard the wash water that collects in the flask.in the flask.

Transfer the sand and filter paper to a Transfer the sand and filter paper to a pre-weighed watch glass and allow pre-weighed watch glass and allow the sand to finish drying. the sand to finish drying.

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

• ProcedureProcedure Heat the solution in the 250 Heat the solution in the 250

mL beaker to boiling. Allow it mL beaker to boiling. Allow it to boil for about 3 minutes to to boil for about 3 minutes to reduce the volume of water in reduce the volume of water in the solution.the solution.

Cool the solution to room Cool the solution to room temperature by placing the temperature by placing the 250 mL beaker into a 600 mL 250 mL beaker into a 600 mL beaker containing 100 mL of beaker containing 100 mL of tap water. Cool the solution tap water. Cool the solution further by placing ice in the further by placing ice in the 600 mL beaker.600 mL beaker.

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fractional CrystallizationFractional Crystallization

• ProcedureProcedure Turn on the aspirator and pour Turn on the aspirator and pour

the mixture containing the the mixture containing the borax crystals onto the borax crystals onto the Büchner funnel.Büchner funnel.

Wash the borax crystals with a Wash the borax crystals with a 10 mL portion of ice water. 10 mL portion of ice water. Continue the suction for 3-4 Continue the suction for 3-4 minutes to help dry the minutes to help dry the crystals.crystals.

Transfer the borax crystals and filter paper to a pre-Transfer the borax crystals and filter paper to a pre-weighed watch glass. Determine the mass of the weighed watch glass. Determine the mass of the borax crystals.borax crystals.

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Fermentation and DistillationFermentation and Distillation

• ProcedureProcedure While waiting for the borax to finish crystallizing, While waiting for the borax to finish crystallizing,

construct the fermentation system shown below for construct the fermentation system shown below for the Fermentation and Distillation experiment.the Fermentation and Distillation experiment.