Q14 of 26 Page 1

Define the following terms:

(i) Adsorption


(ii) Coagulation


(iii) Lyophobic colloid


(i) The phenomenon of accumulation of gas molecules on the surface of solid rather than into the bulk is called adsorption.


(ii) The process of settling of colloidal particles is called coagulaton i.e. conversion of a colloidal solution into a precipitate.


(iii) Lyophobic colloids are those which when mixed with dispersion medium do not form colloids and can be prepared by chemical methods. These are liquid hating substances like metals and their sulphides.


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12

The molar conductivity of 0.025 mol/L methanoic acid is 46.1 Scm2mol-1. Calculate the degree of dissociation and dissociation constant. Given (H+)= 349.6 Scm2mol-1 and (HCOO-)= 54.6 Scm2mol-1.

 13

Show that the time required for the completion of 3/4th of the first order reaction is twice the time required for the completion of half of the reaction.

 15

(i) Write the name of method of refining Ni.

(ii) What is the role of cryolite in the extraction of Aluminium?


(iii) Write one difference between Roasting and Calcination.


 16

Account for the following:

(i) Transition metals form coloured compounds.


(ii) Actinoids show wide range of oxidation states.


(iii) Zinc has lowest enthalpy of atomization in 3d series.


OR


What must be the stable oxidation states of the transition elements with the following configuration in the ground state of their atoms: 3d3, 3d5, 3d8, 3d4