Q21 of 27 Page 1

(a) A colloidal sol is prepared by the given method in figure. What is the charge of AgI colloidal particles in the test tube? How is the sol formed, represented?


(b) Explain how the phenomenon of adsorption finds application in Heterogeneous catalysis.


(c) Which of the following electrolytes is the most effective for the coagulation of Fe(OH)3 sol which is a positively charged ions? NaCl, Na2SO4, Na3PO4

(a) A negative charge is developed in the particles. This occurs because the precipitate adsorbs one of the ions of the electrolyte on its surface.


The sol formed can be represented as AgI/I - .


(b) Heterogenous catalysis is one of the applications of adsorptions -


The reactants get adsorbed on the solid surface of the catalyst. Thus this helps in increasing the rate of reaction.


Manufacture of ammonia by the Haber’s process using iron as a catalyst and manufacture of sulphuric acid by the contact process by using finely divided nickel are some good examples of heterogenous catalysis.


(c) Na3PO4


Reason:


This is determined by the Hardy - Schulze rule. This rule states that greater the valency of the flocculating ion, greater is its power to cause precipitation.


Since, in the above problem PO43 - has the greatest valency it has the greatest coagulating power.


More from this chapter

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19

(a) Name the branched chain component of starch.

(b) Ribose in RNA and deoxyribose in DNA differ in the structure around which carbon atom?


(c) How many peptide linkages are present in a tripeptide?


OR


Give three reactions of glucose which cannot be explained by its chain structure

 20

The following data were obtained during the first order thermal decomposition of N2O5(g) at a constant volume:

2 N2O5(g)2 N2O4 + O2(G)



Calculate the rate constant.


OR


Two reactions of the same order have equal pre exponential factors but their activation energies differ by 24. 9 kJ mol - 1. Calculate the ratio between the rate constants of these reactions at 27°C. (Gas constant R = 8. 314 JK - 1mol - 1. )

 22

Describe how the following steps can be carried out?

(a) Recovery of Gold from leached gold metal complex.


(b) Conversion of Zirconium iodide to pure Zirconium.


(c) Formation of slag in the extraction of copper. (Write the chemical equations also for the reactions involved)


OR


Explain the use of the following:


a) NaCN in Froth Floatation Method.


b) Carbon monoxide in the Mond process.


c) Coke in the extraction of Zinc from Zinc Oxide

 23

Explain the following:

(a) Out of Sc3 + , Co2 + and Cr3 + ions, Sc3 + only is colorless in aqueous solutions. (Atomic no. : Co = 27; Sc = 21 and C = 24)


(b) The E°Cu2 + /Cu for copper metal is positive ( + 0. 34), unlike the remaining members of the first transition series


(c) La(OH)3 is more basic than Lu(OH)3.