Seperation Flashcards
How do you seperate an insoluble solid from a liquid?
Filtration
What happens in filtration?
The liquid filtrate passes through, and the undissolved residue is left on the paper
What do you need for filtration?
2 test tubes, filter paper, funnel
How do you seperate a soluble solid from a solution?
Depends on what you want. If you want the solid, use EVAPORATION. if you want the liquid, use DISTILLATION
The solid part of a solution is called…
the solute
The liquid part of a solution is called…
the solvent
What is filtration used to seperate?
an insoluble solid from a liquid
What is evporation used to seperate?
a soluble solute from a solution
What is distillation used to seperate?
the solvent from a solution with a soluble solute
After distillation, what is the collected liquid called?
distillate
What apparatus is needed for distillation?
Thermometer distillation flask bung heat condenser beaker
What equipment do you use to seperate two immiscible liquids, and what everyday object could you compare this to?
using a seperating funnel (like a gravy jug, but more scientific)
How do you seperate a liquid from a mixture of miscible liquids?
using fractional distillation
What do you need for fractional distillation?
fractionating column, distillation flask, thermometer, condenser, heat
How does fractional distillation work?
-The mixture is heated in a flasks
-The mixture boils and vapours from both liquids pass into the fractionating column.
there is a higher proportion of the substance with the lower boiling point.
In the columnn they condense and reboil repeatedly, each time with a higher proportion of the more liquid with the lower boiling point.
-the vapour from the liquid with the lower boiling point emerges from the column first in a pure state and pass into the condenser
What is the thermometer in fractional distillation used for?
measures the boiling point of the liquid distilling at any moment
(fractional distillation) the liquid with the lower boiling point is called the more ___ liquid
the more volatile liquid
what is chromatography?
A method of separating several solids in a mixture such as dyes
In chromatography, how far will solutes with larger rf values travel?
further
In chromatography, how far will solutes with smaller rf values travel?
less far
What is a chromatogram?
The result of separating liquids with chromatography
In chromatography, why must the water be below the spots?
so the spots don’t dissolve
What does Rf stand for?
retardation factor
What is the solvent front?
How far it (the solvent) travelled
What moves quicker up chromatography paper? More soluble solids, less or neither?
more
How do you calculate Rf value?
Distance moved by pigment / distance moved by the solvent (pigment origin to solvent front)
What is recrystallisation?
The method of purifying a solid and seperating any impurities
How does recrystallisation work?
The solid is dissolved in the minimum amount of hot solvent. it is then filtered to remove any insoluble impurities. The solution is then cooled and the solid crystallizes out of the liquid.
The mixture is filtered again to obtain the solid which is washed with a little cold solvent
What is a seperating funnel used to seperate?
two immiscible liquids
What is fractional distillation used to seperate?
two miscible liquids
(in chromatography) the mobile phase is…
the solvent that moves through the paper carrying the solutes with it
(in chromatography) the stationary phase is…
the paper
What is the difference between fractional distillation and normal distillation
Fractional distillation is used when both liquids will evaporate at the same time, and uses a fractionating column. Distillation can be used for a solid + liquid or two liquids with widely different boiling points.
Why don’t you need a fractionating column for seperating salt from water?
Because the salt won’t evaporate
What type of impurities does the first stage of recrystallisation remove, and what method does it use?
Insoluble, filtration
For the recrystallisation practical, what type of acid, solute solvent do you use
benzoic acid
salt
water
What equipment do you need for recrystallisation and what is each used for?
boiling tube to dissolve acid
filter paper to filter sand
hot funnel to keep benzoic acid dissolved
heat to keep it hot
What type of impurities does the second stage of recrystallisation remove, and what method does it use?
soluble
What will happen when a mixture containing benzoic acid, salt and water is cooled, and how do you do this?
Benzoic acid will recrystallise out
In the second stage of recrystallisation why do you need a glass rod?
To help the formation of crystals
In the second stage of recrystallisation how do you check your recrystallised benzoic acid is pure?
Wash w/ cold water- salt on the acid will dissolve
benzoic acid can only dissolve at higher temperatures
What is another name for the second stage of recrystallisation?
Buchner filtration
What happens when a mixture is heated in simple distillation?
The solvent leaves the solution
A mixture of substances in heated in fractional distillation. Which is collected at the bottom of the column?
The substance with the highest boiling point
What is the best definition of a pure substance?
A substance that consists of only one element or compound
What method is used to obtain copper sulfate crystals from copper sulfate solution?
crystallisation
What is an azeotropic mixture?
Two liquids that can’t be seperated with simple distillation
