2] Distillation : Distillation is used to separate a solvent from a solution,
You remember solution = solvent + solute
So distillation is used to obtain solvent from a solution of different boiling points [main point].
Distillation can also be defined as the method or process of vapourising a liquid and then condensing the water vapour back to liquid.top↑
What is condensation?
Condensation is the process of cooling water vapour with an apparatus called CONDENSER. During boiling of water, some molecules [water vapour] will be trying to escape the surface of the water to the atmosphere, those water molecules can be converted back to water by a condenser.
So back to Distillation,
Distillation can be used to separate a mixture of water and ethanol by distilling the mixture because ethanol and water have different boiling points,
Ethanol has a boiling point of 78°C and water has 100°C, the apparatus needed for the process are the round bottomed flask and a bunsen burner [source of heat].
Ethanol boils at about 78°C while water boils at 100°C, so when heat is apply to the mixture ethanol will vaporize at 78°C leaving only the water, this method is the best to separate ethanol from water because ethanol will vaporize (78°C) before reaching water boiling point(100°C).top↑
2] It can also be use to separate impure water, we all know impurities increases boiling point and reduces melting point.
All pure water are excepted to boil at 100°C, so if a water is not boiling at 100°C that means it contains impurities.
4] Fractional distillation : is the method used to separate two miscible liquids of close boiling point, this method is mainly used in oil refinery, to separate crude oil components which are cooking gas, petrol, diesel, kerosene, oil and the last one bitumen.
That is their serial way of coming out, gas first then petrol follows till the last one bitumen because the all have close boiling point.top↑
Boiling Point Of Crude Oils
Crude oil Boiling point
Other examples are a mixture of benzene and methyl benzene and it can also be use to separate liquefied air to pure nitrogen.top↑
Explanation On Fractional Distillation
Now let me explain fractional distillation of crude oil,
The fractionating column which is packed with glass chips will be inserted into the distilling flask,
In the fractionating column, the liquids vapour of higher boiling point will condense(vapour changing back to liquid) and the liquid will be collected into a flask leaving vapours of low boiling point to get to the condenser before condensing.
I hope you understand now, the main use of fractional distillation is for distilling crude oil.top↑
Next class will be on Separating funnel :
Next Topic :Separating Funnel