anyone can help me decribe the mechanism of fractional distilation??

Answer 1

He is asking for mechanism....Mechanism is how it works. This is a phase equilibria problem. Please refer to A Level option booklet of phase equilibria.

Answer 2

Fractional Distillation Tower Diagram

Answer 3

First they place the substance they want to distillate in the flask, then they add some sillicon stone inside to smooth the heating process.

They then add the fractionating column, on top of the fractionating column, they add a thermometer.

At the side of the fractionating column, they add a condenser, with cool water flowing from the bottom, and the waste water flowing out from the top of the condenser.

So they start distillating either by using a bunsen burner or a electric heater.

At different specific temperature, they collect the desire liquid they want at the end of the condenser, using a conical flask.

To attain as much higher percentage purity as possible, repeated fractional distiltation may be carried out. But it is rather impossible to achieve 100% purity of the desired liquid.

Answer 4

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.

Answer 5

Wikipedia

Answer 6

To Distill Of The Desired Product,, Exactly at the Boiling stages,, For ex: For Acertain Solvent Boils at Certain Temp,, and to get the Fractions of that particular solvent at that particular temperatures,, there by the Mixtures can be separeted in Fractions,, by Refluxing for longer time and Fractionate the solvents

Answer 7

1

Answer 8

Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point, by heating to high enough temperatures.
Fractional Distillation in a Laboratory

Apparatus
round bottom flask
conical flask
fractionating column
liebig condenser
graham condenser
alhin condenser
thermometer
anti-bumping granules
rubber bungs unless quickfit apparatus is used.
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Method
As an example, consider the distillation of a mixture of water and ethanol. Ethanol boils at 78.5 °C while water boils at 100 °C. So, by gently heating the mixture, the most volatile component will concentrate to a greater degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component. In this example, a mixture of 95% ethanol and 5% water boils at 78.2 °C, being more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanol-water mixtures. The apparatus (the diagram represents a batch apparatus, as opposed to a continuous apparatus) is assembled as in the diagram. The mixture is put into the round bottomed flask along with a few anti bumping granules, and the fractionating column is fitted into the top. As the mixture boils, vapor rises up the column. The vapor condenses on the glass platforms, known as trays, inside the column, and runs back down into the liquid below, refluxing distillate. The column is heated from the bottom. The hottest tray is at the bottom the coolest is at the top. At steady state conditions the vapor and liquid on each tray is at equilibrium. Only the most volatile of the vapors stays in gaseous form all the way to the top. The vapor at the top of the column, then passes into the condenser, which cools it down until it liquefies. The separation is more pure with the addition of more trays (to a practical limitation of heat, flow, etc.) The condensate that was initially very close to the azeotrope composition becomes gradually richer in water. The process continues until all the ethanol boils out of the mixture. This point can be recognized by the sharp rise in temperature shown on the thermometer.

In laboratory distillation, several types of condensers are commonly found. The Liebig condenser is simply a straight tube within a water jacket, and is the simplest (and relatively least expensive) form of condenser. The Graham condenser is a spiral tube within a water jacket, and the Alhin condensor has a series of large and small constrictions on the inside tube, each increasing the surface area upon which the vapor constituents may condense. Being more complex shapes to manufacture, these latter types are also more expensive to purchase. Condensers are usually sold by the mm: 100, 200, and 400 mm are common lengths, and are connected to the other vessels with ground glass fittings.
Distillation is the most common form of separation technology in the chemical industry. In most chemical processes, the distillation is continuous steady state, where batch fractionation is not as economical. New feed is always being added to the distillation column and products are always being removed. Unless the process is disturbed due to changes in feed, heat, ambient temperature, or condensing, the amount of feed being added and the amount of product being removed are normally equal. This is known as continuous, steady-state fractional distillation.

The most widely used industrial applications[1][2] of continuous, steady-state fractional distillation are in petroleum refineries, petrochemical plants and natural gas processing plants.


Typical distillation towers in oil refineriesIndustrial distillation is typically performed in large, vertical cylindrical columns known as "distillation or fractionation towers" or "distillation columns" with diameters ranging from about 65 centimeters to 6 meters and heights ranging from about 6 meters to 60 meters or more. The distillation towers have liquid outlets at intervals up the column which allow for the withdrawal of different fractions or products having different boiling points or boiling ranges. The "lightest" products (those with the lowest boiling point) exit from the top of the columns and the "heaviest" products (those with the highest boiling point) exit from the bottom of the column.


Overhead system of an industrial fractionatorLarge-scale industrial fractionation towers use reflux to achieve more complete separation of products.[1][2] Reflux refers to the portion of the condensed overhead liquid product from a distillation or fractionationation tower that is returned to the upper part of the tower as shown in the schematic diagram of the overhead system for a typical, large-scale industrial fractionation tower. Inside the tower, the downflowing reflux liquid provides cooling and condensation of the upflowing vapors thereby increasing the efficacy of the distillation tower. The more reflux provided, the better is the tower's separation of lower boiling materials from higher boiling materials.

Fractional distillation is also used in air separation, producing liquid oxygen, liquid nitrogen, and high purity argon. Distillation of chlorosilanes also enable the production of high-purity silicon for use as a semiconductor.

In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This packing material can either be random dumped packing (1-3" wide) or structured sheet metal. Typical manufacturers are Koch, Sulzer and other companies. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Unlike conventional tray distillation in which every tray represents a separate point of vapor liquid equilibrium, the vapor liquid equilibrium curve in a packed column is continuous. However, when modeling packed columns it is useful to compute a number of "theoretical stages" to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance.

Answer 9

To sum up... different boiling points.

Answer 10

u should go through chapter phase diagrams