Separation Techniques

Question 1

Describe the process of filtration

Answer 1

Place a funnel over a beaker
Place some filter paper in this funnel and pour your mixture into it
The liquid runs through the filter paper, leaving behind, a solid residue

Question 2

Describe the process of crystallisation

Answer 2

Pour the solution into an evaporating dish and gently start to heat
Some of the water will evaporate and solution will get more concentrated
Once crystals start to appear remove the dish from the heat and allow cooling
The salt starts to crystallise as it becomes insoluble in the cold and becomes more concentrated Once crystals
Filter the crystals and leave to dry in a warm place

Question 3

How would you separate rock salt

Answer 3

Grind up using a pestle and mortar
Dissolve in a beaker and stir
Filter using filter paper
Evaporate in an evaporating dish

Question 4

Describe the process of paper chromatography

Answer 4

Draw a line near the bottom of a piece of paper using a pencil so the ink does not dissolve into the solvent
Add spots of samples along the baseline
Place the paper in a beaker containing the solvent, ensuring that the line is above the solvent
Place a lid over the beaker to stop evaporation of the solvent
The solvent moves up the paper, carrying the samples with it
The samples travel at different rates
When the solvent nearly reaches the top of the paper, remove the paper and leave to dry
Chromatogram is left

Answer 5

Pour the solution into an evaporating dish and gently start to heat
Some of the water will evaporate and solution will get more concentrated
Once crystals start to appear remove the dish from the heat and allow cooling
The salt starts to crystallise as it becomes insoluble in the cold and becomes more concentrated
Filter the crystals and leave to dry in a warm place

Question 6

How do you calculate Rf values

Answer 6

Rf = distance travelled by solute / distance travelled by solvent

Question 7

Describe the process of simple distillation

Answer 7

Solution is heated in and the part of the solution with the lowest boiling point evaporates
The vapour is then cooled, and condenses in the condenser before being collected in a beaker
The rest of the solution is left behind in the flask

Question 8

Describe the process of fractional distillation

Answer 8

Place mixture in a flask and stick a fractionating column on top and then heat
Different liquids will all have different boiling points and evaporate at different temperatures
When the temperature of the thermometer matches the boiling point of the liquid, it will reach the top of the Column
Liquids with higher boiling points will condense and run back down to the flask as the top of the column is cooler