CBSE Class 12 Chemistry General Principles and Process of Isolation of Elements Notes and Questions. Based on CBSE and CCE guidelines. The students should practice these Questions to gain perfection which will help him to get more marks in CBSE examination. Based on CBSE and CCE guidelines. The preparation should be in a manner which helps the students to concentrate more in areas which carry more marks.
Important Points :
1. The chemical substances in the earth’s crust obtained by mining are called Minerals.
2. Minerals, which act as source for metal, are called Ore. From ore metal can be obtained economically .
3. The unwanted impurities present in ore are called Gangue.
4. The entire process of extraction of metal from its ore is called Metallurgy.
5. Removal of gangue from ore is called Concentration, Dressing or Benefaction of ore.
6. Concentration by Hydraulic washing is based on the difference in gravities of ore and gangue particles.
7. Concentration by Magnetic separation is based on differences in magnetic properties of ore components. If either of ore or gangue is capable of attracted by a magnet field, then such separation is carried out.
8. Concentration by Froth Flotation Process is based on the facts that sulphide ore is wetted by oil & gangue particles are wetted by water.
9. Concentration by Leaching is based on the facts that ore is soluble in some suitable reagent & gangue is insoluble in same reagent. e.g. Bauxite ore contains impurities of silica, iron oxide & TiO2 .The powdered ore is treated with NaOH which dissolve Al & impurities remains insoluble in it.
Al2O3 +2NaOH + 3 H2O ——→2 Na [Al(OH)4].
10. Calcination involves heating of ore in absence of air below melting point of metal. In this process volatile impurities escapes leaving behind metal oxide.
Fe2O3.xH2O——→ Fe2O3 +xH2O
ZnCO3 ——→ ZnO +CO2
CaCO3.MgCO3 ——→CaO + MgO + 2CO2
11. Roasting involves heating of ore in presence of air below melting point of metal in reverberatory furnace. In this process volatile impurities escapes leaving behind metal oxide and metal sulphide converts to metal oxide.
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