Introduction The purpose of this experiment is to identify unknown liquids by bo
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Introduction The purpose of this experiment is to identify unknown liquids by boiling point combined with density determination and/or IR spectroscopy Procedure Part A. Boiling Point of a Known Liqiud Assemble the apparatus shown (boiling with reflux using a water-iacketed condenser: Reflux apparatus using a water-jacketed condenser (the inset shows an alternative assembly, using an air condenser). Use a 5-mL conical vial containing 3 mL of methanol and a boiling stone. Lower a digital thermometer into the condenser until the end is in the liquid but not touching the bottom or sides -HO of the vial. Secure the thermometer to a ring stand with a thermometer holder. Attach hoses and set the water flow at a very low rate. Have your instructor OK your assembly. Heat at an intermediate rate to reach the boiling point. Gradually reduce the heating rate to the lowest setting that maintains a steady boil. Look for a reflux ring at the bottom of the condenser. When the liquid has been boiling for several minutes, the temperature should be very close to 65 C. If not, continue until it is and record the value below: 1. Observed Boiling Point of Methanol Turn off the heat and raise the vial awav from it hotplate. Let the vial cool for a couple of minutes and dispose of the methanol in the non-halogenated waste container. Rinse the vial and condenser with acetone and let them air dry for a few minutesExplanation / Answer
1a) By escaping the little vapor prevent the system not to be pressurized. Pressure generates when any liquid boils.
1b) If it is plugged with rubber then pressure would be generated and actual pressure will be higher than the atmospheric pressure. The boiling point should be measured at 1 atm pressure.
2a) Boiling point will be higher at higher pressure.
2b) At higher altitude the atmospheric pressure is lower than 1 atm (760 mm of Hg), so the boiling point will be lesser.
2c) Boiling point is a characteristic of the compound and does not depend on the sample size.
2d) Boiling point of the compound does not depend on the amount heat at source.
3. For any liquid when transform it’s phase from liquid to vapor it requires some latent heat. When it absorbs the latent heat, temperature remained constant.
4. Methanol does not form azeoptrope with water and will boil first at 65oC and water will boil at 100oC.
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