Fractional distillation seperation? [!]

Mechanism means how it works, essentially. Different boiling points is what allows this to occur. In a typical fractional distillation, a liquid mixture is heated in the distilling flask, and the resulting vapor rises up the fractionating column. The vapor condenses on glass spurs (known as trays or plates) inside the column, and returns to the distilling flask, refluxing the rising distillate vapor. The hottest tray is at the bottom of the column and the coolest tray is at the top. At steady-state conditions, the vapor and liquid on each tray reach an equilibrium. Only the most volatile of the vapors stays in gas form all the way to the top, where it may then proceed through a condenser, which cools the vapor until it condenses into a liquid distillate. The separation may be enhanced by the addition of more trays (to a practical limitation of heat, flow, etc.).

Fractional Distillation, separation of a mixture of liquids using differences in the liquids’ boiling points. If, for example, a mixture of benzene, which has a boiling point of 80° C (176° F) and methylbenzene (toluene), with a boiling point of 111° C (232° F), is heated slowly from room temperature, the benzene will start to boil off at 80° C. The methylbenzene will remain in the mixture. The temperature will remain constant until all the benzene has vaporized. Then it will rise until it reaches 111° C, when the methylbenzene will boil off. The separated products are called fractions.

An example of fractional distillation is the refining of crude oil. Fractional distillation of crude oil produces fractions with different ranges of boiling points. Each fraction has a particular use. One fraction, boiling between about 70° C (158° F) and 120° C (248° F) is used for petrol. A high-boiling fraction, kerosene, is used for aircraft fuel. Fractions of even higher boiling points are used for fuel oils and for lubricating oils.

Fractional distillation of liquid air separates nitrogen, boiling point -196° C (-321° F), from oxygen, boiling point -183° C (-297° F), and from the other components of air, the noble gases.