Chem33_Lab2_Distillation_KEY_2020.pdf - Last week molecules were separated by their differential polarity on a solid matrix support with an eluent(TLC

Chem33_Lab2_Distillation_KEY_2020.pdf - Last week molecules...

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Last week, molecules were separated by their differential polarity on a solid matrix support with an eluent (TLC).This week, distillation will be used to separate a volatile liquid from a non-volatile dye based on differences inboiling point. The goal of the lab is to use distillation to determine the approximate boiling point of the unknownsolvent, and then use it to determine the identity of the unknown from a list of possible solvents.Before lab:1. Pre-read the laboratory exercise before arriving on time at section in appropriate laboratory attire.2. In your lab notebook, write out a brief laboratory outline of the procedure, which your TA will check during thequiz.a. the goal of the laboratory exerciseb. paraphase the major steps in the exercise, draw the experimental setupc. detail safety hazardsLAB SAFETYHazards:1) Volatile liquids: During this experiment, you will be working with several volatile liquids. Distillation works well withvolatile liquids since they easily vaporize, however one must also use caution as pressure can build up in the flask.It is important to remember that you should NEVER heat a sealed container, as this can result in an explosion. It isalso important not to store volatile liquids near a heat source or in the sun. Please make sure to recap all reagentvials so your volitle liquids do not disappear.2) Hazardous Reagents: Each group will be working with one of three possible unknowns. Because you are notcertain which unknown your group will have, it is important to take the most extreme of the precautions necessary.All reagents are highly volatile and flammable in both the liquid and vapor forms. The possible unknowns are:a) Benzene: A known carcinogen that is off-gased when transferring gasoline. Vapors may cause flash fire.Harmful if swallowed, inhaled, or absorbed through the skin. Continued exposure can lead to irreversible bonemarrow damage and cancer.b) Toluene: A common component of paint thinner, toluene is also a flammable liquid and vapor that can causeeye, skin, and respiratory tract irritation.c) Methanol: A contaminant in moonshine. Methanol is a poison that may be fatal or cause blindness if swallowed.It is a moderate eye and skin irritant.Since all are potential irritants, please wear gloves whenever handling your unknowns and always work in thehoods. Be careful not to spill any on your hot plate as the liquids can ignite.How does Distillation Work?Molecules at the surface of a liquid that have sufficient kinetic energy can escape into the vapor phase (i.e. vaporize).The reverse process (i.e. condense) can be induced by removing energy from molecules using a cooled condenser.A liquid with a lower boiling point has a higher vapor pressure than one with a higher boiling point because the ratio ofmolecules vaporizing to condensing is larger. As temperature increases, the average kinetic energy of the moleculesincreases and the number of molecules with the necessary kinetic energy to enter the vapor phase increases. Withsufficient temperature, the vapor pressure of a pure liquid can equal the external gaseous pressure (e.g. 1 atm), at
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  • Spring '10
  • Dunremember
  • Distillation, Vapor pressure, TA, respiratory tract, ethyne

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