Q12 of 22 Page 1

(i) Name the method of refining to obtain silicon of high purity. (ii) What is the role of SiO2 in the extraction of copper?

(iii) What is the role of depressants in froth floatation process?


(i) Zone refining is the method which is used to obtain high purity silica. This method is useful for producing semiconductor of Si, Ge, B, Ga, etc.


(ii) SiO2 is added so that it combines with iron present in copper ore and forms FeSiO3 (slag) which can then be easily removed. Thus, SiO2 acts as a flux to remove iron from copper ore to get pure Cu.



(iii) In froth floatation, depressant is added to separate 2 sulphide ores. In case the ore contains PbS or ZnS the depressant used is NaCN which prevents ZnS from coming to surface by forming a complex with it.



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10

Calculate the time to deposit 1.27 g of copper at cathode when a current of 2 A was passed through the solution of CuSO4. (Molar mass of Cu = 63.5 g mol−1, 1 F = 96500 C mol−1)

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A solution is prepared by dissolving 10 g of non-volatile solute in 200 g of water. It has a vapour pressure of 31.84 mm Hg at 308 K. Calculate the molar mass of the solute. (Vapour pressure of pure water at 308 K = 32 mm Hg)

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(i) Which one of the following is a polysaccharide : starch, maltose, fructose, glucose

(ii) Write one difference between -helix and -pleated sheet structures of protein.


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(i) What type of isomerism is shown by the complex [Cr(H2O)6]Cl3 ?

(ii) On the basis of crystal field theory, write the electronic configuration for d4 ion if o > P.


(iii) Write the hybridization and shape of [CoF6]3-. (Atomic number of Co = 27)