Give two requirements for vapour phase refining.
(i) The metal should form a volatile compound with available reagent.
(ii) The volatile compound should be unstable and easily decomposable so that the recovery is easy.
Assertion (A): Zirconium can be purified by van Arkel method.
Reason (R): ZrI4 is volatile and decomposes at 1800 K.
Why is an external emf of the more than 2.2 V required for the extraction of Cl2 from brine?
The main reactions occurring in blast furnace during extraction of iron from haematite are
Extraction of gold and silver involves leaching the metal with CN+ ion. The metal is recovered by
(a) displacement of metal by some other metal from the complex ion
(b) roasting of metal complex
(c) calcinations followed by roasting
(d) thermal decomposition of metal complex
The value of ΔfG ° for formation of Cr2O3 is – 540 kJ mol-1 and that of Al203 is – 827 kJ mol-1 . Is the reduction of Cr2O3 possible with Al?
Which of the following statements are correct about the role of substances added in the froth floatation process?
(a) Collectors enhance the non-wettability of the mineral particles.
(b) Collectors enhance the wettability of gangue particles.
(c) By using depressants in the process two sulphide ores can be separated.
(d) Froth stabilizers decrease wettability of gangue.
Why is sulphide ore of copper heated in a furnace after mixing with silica? Iron oxide present as impurity in sulphide ore of copper forms a slag of iron silicate and copper is produced in the form of copper matte.
Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.
What criterion is followed for the selection of the stationary phase in chromatography?
Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?
t the temperature corresponding to which of the points in figure of Q. 11-13, FeO will be reduced to Fe by coupling the reaction 2FeO —> 2Fe + 02 with all of the following reactions?
In the extraction of aluminium by Hall-Heroult process, purified A1203 is mixed with CaF2 to
(a) lower the melting point of A1203.
(b) increase the conductivity of molten mixture.
(c) reduce Al+3 into Al(s).
(d) acts as catalyst.
In which of the following method of purification, metal is converted to its volatile compound which is decomposed to give pure metal?
(a) Heating with stream of carbon monoxide
(b) Heating with iodine
(c) Liquation
(d) Distillation
How are metals used as semiconductors refined? What is the principle of the method used?
At temperatures above 1073 K coke can be used to reduce FeO to Fe. How can you justify this reduction with Ellingham diagram?
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
For the reduction of FeO at the temperature corresponding to point D, which of the following statement is correct?
Assertion (A): Zone refining method is very useful for producing semiconductors.
Reason (R): Semiconductors are of high purity.
Which of the following options are correct?
(a) Cast iron is obtained by remelting pig iron with scrap iron and coke using hot air blast.
(b) In extraction of silver, silver is extracted as cationic complex.
(c) Nickel is purified by zone refining.
(d) Zr and Ti are purified by van Arkel method.
The purest form of iron is prepared by oxidizing impurities from cast iron in a reverberatory furnace. Which iron ore is used to line the furnace? Explain by giving reaction.
Assertion (A): Hydrometallurgy involves dissolving the ore in a suitable reagent followed by precipitation by a more electropositive metal.
Reason (R): Copper is extracted by hydrometallurgy.
In the metallurgy of aluminium
(a) Al3+ is oxidized to Al(s)
(b) graphite anode is oxidized to carbon monoxide and carbon dioxide
(c) oxidation state of oxygen changes in the reaction at anode
(d) oxidation state of oxygen changes in the overall reaction involved in the process.
Choose the correct option of temperature at which carbon reduces FeO to iron and produces CO.
(a) Below temperature at point A
(b) Approximately at the temperature corresponding to point A
(c) Above temperature at point A but below temperature at point D
(d) Above temperature at point A
Although carbon and hydrogen are better reducing agents but they are not used to reduce metallic oxides at high temperatures. Why?
Write down the reactions taking place in blast furnace related to the metallurgy of iron at the temperature range 500-800 K.
Assertion (A): Sulphide ores are concentrated by froth floatation method. Reason (R): Cresols stabilize the froth in froth floatation method.
