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प्रश्न
Explain the following methods to protect metals from corrosion:
Passivation
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उत्तर
Passivation: The surface of metal is treated with strong oxidizing acid such as concentrated nitric acid and a thin preventive layer of oxide is formed on the surface of metal. Thus, the surface is made inactive. This is process is called as passivation.
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संबंधित प्रश्न
Write the names and chemical formulae of any one ore of zinc.
What is the chemical composition of malachite?
- CuO . CuC03
- Cu(OH)2 CuC03
- CuO.Cu(OH)2
- Cu2O . Cu(OH)2
Silica is added to roasted copper ore during smelting process to remove _______.
(A) ferrous sulphide
(B) ferrous oxide
(C) cuprous sulphide
(D) cuprous oxide
Fe2O3 is reduced to spongy iron near the top of blast furance by
(A) H2
(B) CaO
(C) SiO2
(D) CO
In the extraction of Al, impure Al2O3 is dissolved in conc. NaOH to form sodium aluminate and leaving impurities behind. What is the name of this process?
What is the role of coke in the extraction of iron from its oxides?
What is the role of silica in the extraction of copper?
Name the method used for refining of copper metal.
Which among the following minerals does NOT contain aluminium?
(a) Cryolite
(b) Siderite
(c) China clay
(d) Corundum
Draw a neat, well labelled diagram of electrolytic cell for extraction of aluminium
Why does copper obtained in the extraction from copper pyrites have a blistered appearance?
What are the differences between minerals and ores?
Metal which is found in free state is:
Which among the following statement is correct?
The sulphide ore of iron is ____________.
Carbonate ore of iron is ____________.
Which of the following options are correct?
(i) Cast iron is obtained by remelting pig iron with scrap iron and coke using hot air blast.
(ii) In extraction of silver, silver is extracted as cationic complex.
(iii) Nickel is purified by zone refining.
(iv) Zr and Ti are purified by van Arkel method.
In the extraction of aluminium by Hall-Heroult process, purified \[\ce{Al2O3}\] is mixed with \[\ce{CaF2}\] to:
(i) lower the melting point of \[\ce{Al2O3}\].
(ii) increase the conductivity of molten mixture.
(iii) reduce \[\ce{Al^{3+}}\] into \[\ce{Al(s)}\].
(iv) acts as catalyst.
Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.
The important ore of iron is:-
In the electrolytic process for the extraction of aluminium the electrolyte is:-
Which of the following is not ore of aluminium?
In the extraction of iron, the slag produce is
Pyrolusite is ______.
Calamine and Malachite, respectively, are the ores of ______.
The ore that contains both iron and copper is ______.
