Seperation Techniquies

Question 1

Method of separation to separate water from seawater & why

Answer 1

Simple distillation;
water has a a bp of 100, lower than salt
Water will be vaporised and then collected as liquid water (distillate) by condensation by the condenser

Question 2

Method of separation of clay from muddy water & why

Answer 2

Filtration; clay is an insoluble solid
Clay cannot dissolve in water and hence clay particles are larger than the tiny pores of the filter paper, hence it cannot pass through and will be collected as residue

Question 3

Method of separation to separate ethanol from alcoholic beverage & why

Answer 3

Fractional distillation;
Ethanol has a lower bp than water and thus will be vaporised first as it is later collected as a liquid by condensation as it passes through the condenser.

Question 4

Method of separation to separate sugar from sugar cane juice & why

Answer 4

Crystallisation;
Sugar is not heat stable and will be easily composed by strong heating. In order to ensure this does not happen, the juice is heated until a saturated solution is formed. Slowly cooling this solution to room temperature allows sugar crystals to form.

Question 5

Method to separate a dye in food colouring & why

Answer 5

Paper chromatography
Using a suitable solvent, the dyes will dissolve in the solvent as it separates into spots which are located at different positions of the chromatography paper.

Question 6

Separation technique to separate magnesium chloride from its solution & why

Answer 6

Evaporation to dryness
Magnesium chloride salt has a higher boiling point than water, by Vaporising the water, the salt will be the only substance left

Question 7

How to identify a poison dye in food colouring & why

Answer 7

Paper chromatography;
Using a suitable solvent, the dyes will dissolve in the solvent as it separates into spots which are located at different positions of the chromatography paper.
Using the actual poison dye to compare its position on the paper with the other spots of other food colouring.
If it matches, the poisonous dye is present

Question 8

How to separate copper (II) sulfate from its solution & why

Answer 8

Crystallisation;
Copper (II) sulfate crystals is blue when it is hydrated but when the solution is heated strongly for a long period of time, it will form anhydrous copper (II) sulfate which is white instead.

Question 9

How to separate CaCO3 and water & why

Answer 9

Filtration; CaCO3 is an insoluble solid
CaCO3 cannot dissolve in water and hence CaCO3 particles are larger than the tiny pores of the filter paper, hence it cannot pass through and will be collected as residue.

Question 10

How to separate AgCl from AgCl & NaCl and why

Answer 10

Filtration; AgCl is an insoluble solid, NaCl is a soluble solid
AgCl cannot dissolve in water and hence AgCl particles are larger than the tiny pores of the filter paper, hence it cannot pass through and will be collected as residue.

(Water is a suitable solvent)