What are the principles involved in the physical process of separation (mixtures)?

Question

The Separation Techniques:

Distillation

Evaporation

Decantation

chromatography

extraction

Filtration and other separation techniques. please do answer in an organized way. its so hard if its in paragraph.

Answer 1

Distillation: Separation due to difference in boiling temperature. Use it for liquids.

Evaporation: Separation due to difference in boiling temperature. Mostly used to remove a solvent with a LOW boiling temperature. (i.e. ethanol, methanol, water, chloroform, DCM...)

Decantation: Separation due to difference in phase. Use it to remove a liquid from solids.

Chromatography: Seperation due to difference of absorbtion to a column material. It uses the relative difference of polarity of the components combined with their rate of absorbtion to either the eluens or the column material.

Extraction: Seperation due to the difference of the solubility of a solid or liquid in relation to two other liquids. The desired compound will go in to one of the two liquids which DON'T mix. You just collect the desired liquid and you have your compound.

Filtration: Seperation due to difference of molecular size. Mostly used to seperate crystals or other insoluble material from liquids.

Answer 2

Distillation makes use of the difference in boiling points of the substances to be separated. The more volatile substance is boiled off, then condensed into liquid form.

Evaporation makes use of boiling point difference as well. Here, however, the more volatile substance is simply boiled off without condensing. It is often done when the substance of interest is normally a solid.

Decantation is the "pouring off" of a liquid from a solid/liquid mixture. The mixture is allowed to settle, and the liquid is removed while preventing the solid from escaping.

Chromatography utilises the difference in affinity substances have for a particular surface. If the substance is polar, it will stick to a polar surface, whereas non-polar substances will not stick to a polar surface. Hence, the substances will be separated.

Extraction depends on the difference in solubility of the mixture components in certain solvents. For example, if a substance is soluble in water, but even more soluble in hexanol, it will leave the water and dissolve in the hexanol. Because hexanol and water don't mix, the two layers can be separated, and the substance of interest can be extracted selectively.

Filtration depends on particle size, and is used to separate solids and liquids. Coarse solid particles are trapped by the filtration medium, such as filter paper, whereas the solvent will pass through, allowing the solid and liquid to be separated.

Answer 3

I will try to be specific:

Distillation---- Any solvent has specific temp at which it boils at certain pressure. By using this you can separate / purify.

Evaporation: Same as distillation but it will be very time consuming and not economical.

Decantation--- The principle here is to seperate solids from solution.

chromatography: there are several types of chromatographic techniques such as thin layer chromatography, Gas chromatography,

HPLC (High Pressure Liquid Chromatography).

And each one is based on different principle.(A standard chemistry book will be very useful)

extraction--- This technique is based on a Selective Dissolution of a specific subsance.

I hope this will help you.

08-06-08

Wednesday

KishoreKChokshi2 yahoo.com

Answer 4

the previous answers give good summaries of the separation techniques.  

Another method you can include is electrophoresis, in which you are separating compounds in an electric field based on their surface charge.

Answer 5

Reversible.i.e evaporation can cool an form water an evaporate again.   When u distillate something with temperature it is inreversible.(just like toast bread)   Decantation is when removing im purities from a substance.(reversible)    Chromatography i.e seperating colours an dyes(reversible seperate blue an yellow an join them again.   Extraction is also