Q14 of 26 Page 1

What happens when

(a) a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount of FeCl3 solution?


(b) persistent dialysis of a colloidal solution is carried out?


(c) an emulsion is centrifuged ?

(a) When freshly prepared precipitate of Fe(OH)3 is shaken with a small amount of FeCl3 solution, a positively charged sol of Fe(OH)3 is formed due to adsorption of Fe3+ ions.

(b) On persistent dialysis, a colloidal solution traces of electrolyte is completely removed leaving colloids unstable, and finally, coagulation takes place


(c) On centrifugation of emulsion, separation of the two constituent liquids will take place.


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A first order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction.

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(a) E° value for Mn3+/Mn2+ couple is much more positive than that for Fe3+/Fe2+


(b) Iron has higher enthalpy of atomization than that of copper.


(c) Sc3+ is colourless in aqueous solution whereas Ti3+ is coloured.