what is the principal used in the separation of mixture?
Answers
Explanation:
Separation of Mixtures
Mixtures can be separated using a variety of techniques.
1. Chromatography
Chromatography is the separation of a mixture by passing it in solution or suspension or as a vapor (as in gas chromatography) through a medium in which the components move at different rates. Thin-layer chromatography is a special type of chromatography used for separating and identifying mixtures that are or can be colored, especially pigments.
Paper chromatography
Paper chromatography uses ordinary filter paper as the medium upon which the mixture to be separated is applied. Thin-layer chromatography (abbreviated TLC) uses a thin coating of aluminum oxide or silicagel on a glass microscope slide or plastic sheet to which the mixture is applied. A single drop of the unknown mixture to be separated is applied about half an inch from the end of a strip of filter paper or TCL slide. The filter paper or TLC slide is then placed in a shallow layer of solvent in a jar or beaker. Since filter paper or the TLC slide coating is permeable to liquids, the solvent begins rising up the paper by capillary action.
As the solvent rises to the level of the mixture spot, various effects can occur, depending on the constituents of the spot. Those components of the spot that are completely soluble in the solvent will be swept along with the solvent front as it continues to rise. Those components that are not at all soluble will be left behind at the original location of the spot. Most components of the mixture will move up the paper or slide at an intermediate speed somewhat less than the solvent front speed but not remaining at the original spot either. In this way, the original spot of mixture is spread out into a series of spots or bands, with each spot representing one single component of the mixture. The separation of a mixture by chromatography is not only a function of the solubility in the solvent used. The filter paper or TLC coating consists of molecules that may interact with the molecules of mixture as they are carried up the medium. The primary interaction between the mixture components and the medium is due to the polarity of the components and that of the medium. Each component of the mixture is likely to interact with the medium to a different extent thus slowing the components of the mixture differentially depending on the level of interaction.
column chromatography
In this form, a vertical column is filled with solid absorbent, the mixture is poured in at the top, and a carrier solvent is added. As the mixture flows down the column, the components are separated, again, by differing solubilities in the carrier solvent and different absorbencies to the solid packing. As the liquid drips out the bottom of the column, components of the solution will exit at different times
2. Distillation
Distillation is an effective method to separate mixtures comprised of two or more pure liquids. Distillation is a purification process where the components of a liquid mixture are vaporized and then condensed and isolated. In simple distillation, a mixture is heated and the most volatile component vaporizes at the lowest temperature. The vapor passes through a cooled tube (a condenser), where it condenses back into its liquid state. The condensate that is collected is called distillate.
3. Evaporation
Evaporation is a technique used to separate out homogenous mixtures where there is one or more dissolved solids. This method drives off the liquid components from the solid components. The process typically involves heating the mixture until no more liquid remains, Prior to using this method, the mixture should only contain one liquid component, unless it is not important to isolate the liquid components. This is because all liquid components will evaporate over time. This method is suitable to separate a soluble solid from a liquid.
In many parts of the world, table salt is obtained from the evaporation of sea water. The heat for the process comes from the sun.
4. Filtration
Filtration is a separation method used to separate out pure substances in mixtures comprised of particles some of which are large enough in size to be captured with a porous material. Particle size can vary considerably, given the type of mixture. For instance, stream water is a mixture that contains naturally occurring biological organisms like bacteria, viruses, and protozoans. Some water filters can filter out bacteria, the length of which is on the order of 1 micron. Other mixtures, like soil, have relatively large particle sizes, which can be filtered through something like a coffee filter.