Q12 of 26 Page 1

(i) Indicate the principle behind the method used for refining of Zinc.

(ii) What is the role of silica in the extraction of copper?


(iii) Which form of Iron is the purest form of commercial iron?


(i) Zinc is refined by electrolysis method. The principle involved in this method is that the impure zinc is made anode while a thin strip of pure zinc is made the cathode, both of them are dipped in a zinc salt solution which acts as electrolyte. When electricity is passed through this circuit, the impure zinc metal at anode gets oxidised and come into the electrolyte


while the zinc ions reduce at cathode to form pure zinc (solid) metal.



(ii) The ores of copper usually contain iron oxide(FeO) as impurity, to remove this impurity silica(SiO2) is added. This silica reacts with iron oxide to form iron silicate (FeSiO3) which can be removed as slag.



(iii) Wrought iron is the purest form of iron with only 0.12-0.25% of carbon present after purification.


More from this chapter

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10

(a) Following reactions occur at cathode during electrolysis of aqueous silver chloride solution:


On basis of their standard reduction potential (E0) values, which reaction is feasible at cathode and why?


(b) Define limiting molar conductivity. Why conductivity of an electrolytic solution decreases with the decrease in concentration?


 11

3.9g of benzoic acid dissolves in 49g of benzene shows a depression in freezing point of 1.62K. Calculate the van’t Hoff factor and predict the nature of solute (associated or dissociated).

(Given: molar mass of benzoic acid =122g mol-1, Kf of benzene =4.9K Kg mol-1)


 13

An element with molar mass 27g mol-1 forms a cubic unit cell with an edge length of 4.05 x 10-8cm. If its density is 2.7g cm-3, what is the nature of cubic unit cell?

 14

(a) How would you account for the following?

(i) Actinoid contraction is greater than Lanthanoid contraction.


(ii) Transition metals form coloured compounds.


(b) Complete the following equation: