Cuprite: $$\,Cu{O_2};$$ Chalcocite : $$C{u_2}S;$$ Chalcopyrite : $$CuFe{S_2};$$
Malachite: $$Cu{\left( {OH} \right)_2}.CuC{O_3}.$$ We see that $$CuFe{S_2}\,$$ contais both $$Cu\,{\text{and}}\,Fe.$$
133.
Cryolite is
A
$$N{a_3}Al{F_6}$$ and used in the electrolysis of alumina for decreasing electrical
conductivity
B
$$N{a_3}Al{F_6}$$ and used in the electrolysis of alumina for lowering the melting point of alumina
C
$$N{a_3}Al{F_6}$$ and used in the electrolytic purification of alumina
D
$$N{a_3}Al{F_6}$$ and used in the electrolysis of alumina
Answer :
$$N{a_3}Al{F_6}$$ and used in the electrolysis of alumina for lowering the melting point of alumina
136.
The powdered ore is agitated with water or washed with running stream of water. The heavy ore particles and lighter impurities are separated. This method of concentration is known as
No explanation is given for this question. Let's discuss the answer together.
137.
Which of the following changes take place during roasting?
(i) Impurities are removed as their volatile oxides.
(ii) Ore is converted into its oxide.
(iii) Changes like oxidation, chlorination, etc. take place.
In the metallurgy of aluminium, purified $$A{l_2}{O_3}$$ is mixed with $$N{a_3}Al{F_6}\,\,{\text{or}}\,\,Ca{F_2}$$ which lowers the melting point of the mix and brings conductivity.
140.
The method of zone refining of metals is based on the principle of :
A
Greater solubility of the impurity in the molten state than in the solid
B
Greater mobility of the pure metal than that of the impurity
C
Higher melting point of the impurity than that of the pure metal
D
Greater noble character of the solid metal than that of the impurity
Answer :
Greater solubility of the impurity in the molten state than in the solid
Zone refining is based on the difference in solubility of impurities in molten and solid state of the metal. This method is used for obtaining metals of very high purity.