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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.
Write the names and chemical formulae of any one ore of iron.
Write the reactions involved in the zone of reduction in blast furnace during extraction of iron.
Silica is added to roasted copper ore during smelting process to remove _______.
(A) ferrous sulphide
(B) ferrous oxide
(C) cuprous sulphide
(D) cuprous oxide
Write chemical formulae of the following ores :
(a) Calamine
(b) Haematite
(c) Magnetite
(d) Corundum
Out of C and CO, which is a better reducing agent at the lower temperature range in the blast furnace to extract iron from the oxide ore?
Mention names and formulae of two ores of alumunium.
What is the role of cryolite in the extraction of aluminium?
Indicate the principle behind the method used for the refining of zinc.
Define leaching.
Explain the following methods to protect metals from corrosion:
Galvanization
Draw a neat, well labelled diagram of electrolytic cell for extraction of aluminium
The chemical formula of willemite is __
(a) ZnS
(b) ZnCO3
(c) ZnO
(d) Zn2SiO4
What is 'copper matte' ?
A current liberates 0.50 g of hydrogen in 2 hours. The weight of copper (at. wt. = 63.5) deposited at the same time by the same current through copper sulphate solution is ______.
Describe the role of the cryolite in the extraction of aluminium from pure alumina.
Bauxite has the composition
The most abundant metal on earth is:
Carbonate ore of iron is ____________.
When copper ore is mixed with silica, in a reverberatory furnace copper matte is produced. The copper matte contains ______.
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.
Although carbon and hydrogen are better reducing agents but they are not used to reduce metallic oxides at high temperatures. Why?
Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.
Identify a mineral for the major source of boron from the following list?
In the thermite process, the reducing agent is:
When compared to ΔG° for the formation of Al2O3 ΔG° for the formation of Cr2O3 is
Which of the following is not an ore of magnesiuim?
In the extraction of iron, the slag produce is
The ore that contains both iron and copper is ______.
