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General Principles And Processes Of Isolation Of Elements
Explain the role of each of the following:
(i) NaCN in the extraction of silver
(ii) SiO2 in the extraction of copper
(i) The roasted ore of gold is leached with a solution of sodium cyanide in the presence of oxygen for many days. The role of NaCN in this process is to dissolve the gold to form an aurocyanide complex, from which the metal is obtained by displacement.
4Au + 8NaCN + 2H2O + O2 ---> 4 Na [Au(CN)2] + 4KOH
2Na[Au(CN)2] + Zn ---> Na2[Zn(CN)4] + 2Au
(ii) Copper matte contains Cu2S and FeS. In the blast furnace, copper matte is added with powdered coke and silica. The oxidation of ore takes place in this process. As a result, cuprous oxide and ferrous oxide are produced. The role of silica in this process is to remove the iron oxide obtained as ‘slag’. FeO combines with silica (flux) to form iron silicate, FeSiO3(slag).
FeO + SiO2 
FeSiO2
Flux slag
Some More Questions From General Principles And Processes of Isolation Of Elements Chapter
Titanium is a metal of modern times. It is obtained as oxide. Why it could not be extracted earlier despite its wide occurence?
Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present?
What criterion is followed for the selection of the stationary phase in chromatography?
What is the role of cryolite in the metallurgy of aluminium?
Why is zinc not extracted from zinc oxide through reduction using CO?
What is the role of graphite rod in the electrometallurgy of aluminium?
Predict conditions under which Al might be expected to reduce MgO.
Define the term gangue or matrix.
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