Separation of Mixtures part 3

Alfred Ajibola - Wed, 26th June, 2019 @ 06:14: AM

Topics in Chemistry

Salts and Types of Salt in Chemistry Mixtures and Separation of Mixtures Separation of Mixtures part 2 Separation of Mixtures part 3 Physical Change, Chemical Change, Element, Compound and Mixture Electrolysis, Electrolyte, Electrode, Anode and Cathode Grahams law of diffusion Physical Properties of Metals Daltons Atomic Theory and its Modifications Periodic table and Classification of Elements

Academic Questions in Chemistry

Please check out our Test Your Knowledge page to see all Questions and Answers

The reaction involving an acid and a base is termed _____.

  • A. Hydrolysis
  • B. Neutralization
  • C. Combustion
  • D. Displacement
  • E. Decomposition
  • F. Sublimation

Which of the following is NOT a type of salt?

  • A. Acid salt
  • B. Basic salt
  • C. Double salt
  • D. Tripple salt
  • E. Complex salt
  • F. Normal Salt

The only metal that exist as liquid at room temperature is _____.

  1. Nickel
  2. Duralumin
  3. Mercury
  4. Lead
  5. Titanium
  6. Cesium

Separation of Mixtures:

Please read part 1 here


(7) Fractional Distillation

Fractional distillation is a method used for separating a mixture that contains more than two miscible liquid; and with a close range of boiling points. A typical example of liquid separated by this method is petroleum or crude oil.

If the difference in boiling point is greater than 250C, a simple distillation should be used.

Crude oil contains various fractions and these can be separated via fractional distillation. The fractions are listed below from the most volatile to the least volatile:

  • Fuel gas (most volatile)
  • LPG
  • Refinery gas
  • Gasoline
  • Petrol
  • Naphtha
  • Paraffin
  • Kerosene
  • Diesel oil 
  • Gas oil
  • Fuel oil
  • Lubricating oils
  • Wax
  • Bitumen (least volatile)

Image Credit: Gradeup School

An important apparatus that makes fractional distillation possible is the fractionating column

On heating the mixture (e.g crude oil), the vapours move into the fractionating column (since their boiling points are of a close range). The fractions with a high molecular mass have higher boiling points and condense at lower portions of the column while fractions with lower molecular mass rise to the top of the column to condense. The fraction with lower boiling point (less molecular mass and more volatile) distills into the condenser and is collected as the first distillate. The other liquids with a higher boiling are also collected in a similar way. Please read on molecular mass and molar mass here.


(8) Precipitation

Precipitation is a method used to separate ions in aqueous solution.

Consider an aqueous solution as one that contains water as its solvent

Now, if two ions are present in an aqueous solution, let’s say copper ions (Cu2+) and silver ions (Ag+); one of the ions can be precipitated out if we added another solvent (for instance hydrochloric acid *HCl*)  into the aqueous solution.

On addition of HCl in the above instance, silver ions (Ag+) will be precipitated out of the aqueous solution as silver chloride (AgCl) while the copper ions (Cu2+) will still remain in the aqueous solution.

Ag+(aq) + Cu2+(aq) + Cl-(aq) -> AgCl(s) + Cu2+(aq)

Please read introduction to electrolysis here to get the concept of ions.

Note: The process of precipitation can also be applied in the purification of impure compounds.


Other techniques utilized in the separation of mixtures are:

  • Magnetization

Magnetic separation is used to separate substances that attracted to magnets from those that don’t.

A mixture of iron filings and sulphur can be separated via magnetization.


  • Crystallization

Crystallization is a separation technique used for separating two salts with different solubilities.

It is also used for the purification of a soluble salt that contains insoluble solid impurities.


  • Chromatography

It is used to separate components of a complex mixture in solution, for instance ink.

Below are some types of chromatography:
  • Paper chromatography
  • Column chromatography
  • Gas chromatography
  • Thin layer chromatography

Please read part 2 here


Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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Amazing facts in Chemistry

The only letters that failed to appear on the periodic table are letters:

J     &     Q

Gold and copper are the only two non-silvery colored metals. Please read some interesting facts about gold here