Separation and Purification Techniques (Methods for separation(Liquids)…
Separation and Purification Techniques
What is a pure substance?
It is a substance that is made up of only one element or compound. It is not mixed with any other subsatnce
Why is it important to determine if a substance is pure?
to prevent any side effects
How to determine the purity of the substance
Melting point of a solid
A pure solid will have a fixed and constant M.P.
If the solid is impure, it will lower the M.P.
The higher the amt. of impurities, the lower the melting point of the solid.
It will cause melting to take place over a range of temperatures
Boiling point of the liquid
A pure liquid will have a fixed and a constant B.P
The presence of impurities will increse the B.P of the liquid
The higher the amt. of impurities in the liquid, the lower the boiling point
It will cause boiling to take place over a range of temperatures.
We use ethanol as the solvent and see if the liquid is made up of more than one compound
Pressure on the liquids: the higher the pressure, the higher the boiling point
Methods for separation(Liquids)
Used to separate insoluble subsatnces(solid) from a liquid
The pores in the filter paper allows the liquid to flow through, while the insoluble solid will remain on the filter paper
Residue=insoluble solid, Filterate=liquid collected in the flask
Used to separate a soluble subsatnce to separate from a liquid
however the water will be lost to the atmosphere
solid obtained may be impure
Used to separate soluble solid that decomposes upon heating
Liquid is removed by heating the solution
Heating is stopped once a hot saturated solution is formed
Allow the solution too cool down till room temperature
The soluble solid will gradually form crystals, filter the saturated solution. Dry the crystals between pieces of filter paper
Method of boiling the liquid and condensing the vapour
Pure liquid can be obtained from this method
Place the thermometer at the side arm of the flask. Do not dip it inside the solution. It is to ensure that the thermometer measures the temperature of the vapour that is being distilled dover.
At the outer jacket of the condenser, cold running water enters the jacket from the bottom and leaves from the top
This is to ensure that the coolest part is just before the vapour escapes
Used to separate miscible liquids
The liquid with the lowest B.P. will distill over to the condenser
Vapour of the liquids with higher B.P. will condense along the fractionating column and re-enter the flask
Collection of gases
soluble in water and less dense than air---upward delivery
insoluble in water--displacement of water
soluble in water and denser than air---downward delivery