1. What is the difference between Hydrometallurgy and Pyrometallurgy?

2. what are the two aspects considered during reduction of metals?

1) Hydrometallurgy is a technique in which the metal to be extracted is brought into a solution by using suitable chemical reagents followed by recovery of metal by use of proper precipitating agent ( a more electropositive metal.) Example: low grade copper ore is leached by treating with acid where copper metals goes into the solution as copper ions which is then treated with iron or hydrogen to obtain solid copper.

Pyrometallurgy is a method of metallurgy which deals with the methods of extraction of metals from their ores and their refining at at high temperatures, i.e. 500-2000°C.The metallurgical reactions are made to take place at elevated temperatures because than the ore compounds become relatively unstable, facilitating the release of the metal. Pyrometallurgical methods of metal production are usually cheaper and suited for large scale productions. Pyrometallurgy can bring about the reduction of a compound, which cannot take place in presence of water i.e. it has got ability to extract the reactive metals which can’t be reduced from aqueous solutions. Ex. Alkaline earth metals, zirconium, titanium etc.

2) Thermodynamic and electrochemical aspects are considered during reduction of ores to metal.
Electrochemical aspects deal with the conversion of concentrated ore into oxide and subsequent reduction to metal.The various methods involved are: roasting, calcination, reduction using a suitable reducing agent.
Thermodynamic aspects include Gibbs free energy changes during the chemical reactions.The graphical representation of Gibbs free energy known as Ellingham diagrams are used to choose the reducing agent in the reduction of oxides.

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