Fractional Distillation vs Distillation
Distillation is a method to separate components from a mixture of liquids. This is widely used in industries and laboratories and is a very successful method.
Distillation
蒸馏是一种物理分离方法is used to separate compounds from a mixture. It is based on the boiling points of the components in the mixture. When a mixture has different component with different boiling points, they evaporate at different times when we are heating. This principle is used in the distillation technique. If there are two substances in a mixture as A and B, we will assume A has the higher boiling point. In that case, when boiling, A will evaporate slower than B; therefore, the vapor will have a higher amount of B than A. So the proportions of A and B in the vapor phase are different from the proportions in the liquid mixture. The conclusion is that, the most volatile substances will be separated from the original mixture whereas less volatile substances will be remained in the original mixture.
In a laboratory, a simple distillation can be carried out. When preparing an apparatus, a round bottom flask should be connected to a column. End of the column is connected to a condenser and cold water should be circulated in the condenser so that when vapor travels through the condenser it gets cooled. Water should travel the opposite direction of the vapor which allows maximum efficiency. The end opening of the condenser is connected to a flask. The entire equipment should be air sealed so that the vapor won’t escape during the process. A heater can be used to supply the heat to the round bottom flask which contains the mixture to be separated. Since all the volatile compounds tend to evaporate when the heat is supplied, the vapor will contain a mixture of volatile compounds. The ratio of compounds in the mixture can be determined according to their ratio in the original mixture. According to the Raoult’s law, mixture’s composition will be identical to the composition of the vapors at the given temperature and pressure. When heating the vapor moves up the column and goes into the condenser. When it travels inside the condenser, it becomes cool and liquefies. This liquid is collected to the flask kept at the end of the condenser, and it is the distillate.
Fractional Distillation
When the components in the mixture have closer boiling points, we can use fractional distillation method to separate them out. A fractional column is used in this method. At each level of the fractionating column, the temperature will be different, so the components related to that the temperature will remain in that section as vapor while other are condensed back to the round bottom flask.
What is the difference between Distillation and Fractional Distillation? • Fractional distillation is one of the distillation methods. • In the fractional distillation method, a fractionating column is used in contrast to other distillation methods. • When the components in the mixture have closer boiling points, fractional distillation method is used. When they have a large difference in their boiling points, simple distillation can be used. • Raoult’s law can be neglected in the simple distillation but, in fractional distillation, it is taken into consideration. |
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