I/GCSE Chemistry - Separation Techniques

Liquids can be separated in 2 ways depending on whether they are miscible or immiscible. In I/GCSE Chemistry you will have to know the 3 main separation techniques: Fractional distillation, Separating Funnel and Chromatography.

Miscible Liquids🤨

Miscible liquids can be separated using fractional distillation, its hard to separate the liquids as they have dissolved in one another but it impossible to do as each different liquid has different boiling points 

Fractional distillation of liquid air-

• About 78% of the air is nitrogen and 21% oxygen. The gases can be separated by fractional distillation of liquid air. 

1. Water vapour condenses and is removed using absorbent filters
2. Carbon dioxide freezes at -79ºC and is removed
3. Oxygen liquefies at -183ºC
4. Nitrogen liquifies at -196ºC
5. The liquid nitrogen and oxygen are then separated in fractional distillation.

Immiscible Liquids🤯

Immiscible means that the liquids don't dissolve in each other separating immiscible liquids is done using a separating funnel. 

1. The two liquids are put into a separating funnel and left for a short time to settle out and form two layers. 
2. The tap of the funnel is opened and the bottom liquid is allowed to run. The two liquids are not separate. 

Chromatography 🌈

Chromatography is used to separate mixtures of coloured compounds. Mixtures that are suitable for separation by chromatography include inks dyes and colouring agents in foods. Simple chromatography is carried out on paper. 

1. A spot of the mixture is placed near the bottom of chromatography paper and the paper is then placed upright in a suitable solvent.
2. As the solvent soaks up the paper, it carries the mixtures with it. 
3. Different components of the mixture will move at different rates. 
4. This separates the mixture out. 

The RF Values 

Different chromatograms and the separated components of the mixture can be identified by calculating the RF Value by using the equation:

distance moved by the compound/distance moved by the solvent 

The RF of a particular compound is always the same if the chromatography has been carried out in the same way allowing industry to use chromatography to identify compounds in mixtures.

References; https://lh3.googleusercontent.com/proxy/wXdJIMVM0UQiHnMdVSyBIVUIDizkMdKpg9FPxOIdDy1-sLRq4a2FOiGjquuqqz0AHfByeHoG4jEdYTaUqW_b-a6zdqf2Q-vnwwOHcXYuM5Y6_zrKTcAXQjdOcQ4solqxq9Dk1f0OOxSrVtEhXCSO6Q

https://image.shutterstock.com/image-illustration/illustration-chemistry-separatory-funnel-composition-260nw-1400098556.jpg

https://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/Chromatography_tank.png/220px-Chromatography_tank.png

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Drafted by Catrina (Chemistry)