Q14 of 50 Page 1

Describe the principle controlling each of the following processes:

(i) Vapour phase refining of titanium metal.


(ii) Froth floatation method of concentration of a sulphide ore.


(i) Vapour phase refining of titanium metal.


In this method, first, the metal titanium is converted into its volatile compound (like its iodide) and collected elsewhere. Next, it is then decomposed to give pure metal.



(ii) Froth floatation method of concentration of a sulphide ore.


Sulphide ores are preferentially wetted by oils while the gangue is preferentially wetted by water .The ore particles get adsorbed on oil droplets and come to the surface where they can be collected as froth gangue is wetted by water and gets settled down. Eg. It is done for PbS ores.


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What do you understand by the rate law and rate constant of a reaction? Identify the order of a reaction if the units of its rate constant are:

(i) L-1mol s-1


(ii) L mol-1 s-1


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The thermal decomposition of HCO2 H is a first order reaction with a rate constant of 2.4 x 10-3 s-1 at a certain temperature. Calculate how long will it take for three- fourths of initial quantity of HCO2H to decompose. (log 0.25 = -0.6021).

 15

How would you account for the following:

(i) Cr2+ is reducing in nature while with the same d-orbital configuration (d4) Mn3+ is an oxidizing agent.


(ii) In a transition series of metals, the metal which exhibits the greatest number of oxidation states occurs in the middle of the series.


 16

Complete the following chemical equations :
(i)

(ii)


OR


State reasons for the following :
(i) Cu (I) ion is not stable in an aqueous solution.
(ii)Unlike Cr3+, Mn2+, Fe3+ and the subsequent other M2+ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species.