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Define the following -
1. Calcination
2. Roasting
3. Thermit Rxn..
Answers
Roasting : It is the process of converting an ores to oxide by strongly heating it in the presence of excess of air . ...
Calcination : It is the process of converting an ores to oxide by strongly heating it in limited air . For example carbonate ores are converted into the oxide by heating in the absence of air.
Thermite Reaction:
Thermite is a pyrotechnic composition of metal powder, which serves as fuel, and metal oxide. When ignited by heat, thermite undergoes an exothermic reduction-oxidation reaction. Most varieties are not explosive, but can create brief bursts of heat and high temperature in a small area.
Calcination
The heating of solids to a high temperature for the purpose of removing volatile substances, oxidizing a portion of mass, or rendering them friable. Calcination, therefore, is sometimes considered a process of purification.
Roasting
Roasting is a process of heating of sulphide ore to a high temperature in presence of air. In roasting, the ore or ore concentrate is treated with very hot air. This process is generally applied to sulfide minerals. During roasting, the sulfide is converted to an oxide, and sulfur is released as sulfur dioxide, a gas.
Thermit Rxn
The thermite reaction is an exothermic reaction between the metal and metal oxide. For example the reaction between the aluminium with the metal oxides, where aluminium acts as a reducing agent. The reaction is used for thermite welding. The reaction is used to connect railway tracks.