Extraction of Metal from Ore

  • It is the process of extracting metal from its concentrated ore . It is the next step after concentration of ore.
  • The extraction method depends upon the reactivity series of metals .



Extraction of Less Reactive metals in the Reactivity Series

Metals low in the reactivity series are very unreactive . The oxides of these metals can be reduced to metals by heating alone.

 

These include Metals like Mercury and Copper

 

  1. Mercury Sulphide (HgS) or Cinnabar is the ore of mercury
    Mercury can be directly extracted from its sulphide ore by heating it in air.
    The process involves two steps:
    Conc. Mercury (II) Sulphide ore, Cinnabar, is roasted in air.

Mercury Oxide is formed .

The oxide is heated to about 300℃.

It gets reduced to form Mercury metal.

 

(II) Extraction of Copper

Conc. Sulphide ore Cu 2 S is roasted in air to form Copper Oxide.

 

When enough Cu 2 S has been converted to Cu 2 O, the supply of air is cut.

Cu 2 O reacts with the remaining Cu 2 Sto form Cu.

 

 

Extraction of moderately reactive metals :

 

In order to be extracted, these are reduced from their oxides , with reducing agents like carbon, aluminium, sodium or calcium.

  • It is easier to obtain metals from their oxides than from carbonates or sulphides.
  • Thus, the concentrated ores are converted into metal oxide by the process of calcination or roasting .
  • A carbonate ore is converted into oxide by calcination whereas a sulphide ore is converted by roasting .

 

  1. CALCINATION :
  • The carbonate ore is heated strongly in the absence of air to convert it into metal oxide.
  • Example - Calamine ore, ZnCO 3  

In order to extract zinc metal from this ore, it must first be converted into zinc oxide from zinc carbonate. This is done by Calcination.

The reaction is as follows :

 

  1. ROASTING :
  • The sulphide ore is strongly heated in the presence of air to convert it into metal oxide. 
  • Example - Zinc occurs as a sulphide ore, ZnS

This sulphide is first converted to oxide by the process of roasting and then the zinc metal is extracted from it. 

The reaction is as follows  :



Extraction of Reactive Metals 

 

  • The highly reactive metals like Potassium, Sodium, Calcium, magnesium and aluminium do not have stable oxides.
  • These cannot be reduced by carbon (reducing agent).

 

These metals are extracted by the electrolytic reduction of their molten chlorides or oxides

In electrolytic refining,

  1. Impure Metal M is used as anode
  • It is connected to the positive terminal of the battery.
  1. A strip of pure metal M is used as a cathode
  • It is connected to the negative terminal of the battery.
  1. A solution of metal salt M is used as the electrolyte .

For example 

NaCl → Na + (l) + Cl (l)

  • During electrolysis , the negatively charged electrode ( cathode ) acts as a powerful reducing agent .
  • It supplies electrons to reduce the metal ions into metal
  • This is because metals being positively charged ions are attracted towards the negatively charged cathode. 

 

At cathode: reduction of 2Na + (l) + e → Na(l)

  • The anode provides a strong positive charge to attract the anions .
  • It oxidises the anions to form Chloride gas/Oxygen .

At anode: oxidation of 2Cl (l) → Cl 2 (g) + 2e

Net Reaction is written as: 2Na + (l) + 2Cl (l) → 2Na(l) + Cl 2 (g)

 

 

Example : Sodium , Potassium , Calcium and Magnesium are extracted by electrolysis of their molten chlorides whereas Aluminium metal is extracted by electrolysis of its molten oxide .

  1. Class 10
  2. Chapter 3 Class 10 - Metals and Non-Metals (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo