Q22 of 27 Page 1

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

(a) The leached gold complex is treated with Zinc.


2Au[(CN)2] - (aq) + Zn (s)2Au (s) + [Zn(CN)4]2 -


The gold is recovered by a displacement reaction.


(b) Zirconium Iodide is decomposed on a tungsten filament which is electrically heated at 1800 K. The pure metal is thus deposited on the filament.


ZrI4Zr + 2I2


This is a part of the van Arkel method for refining Zirconium.


(c ) In the extraction of copper, silica is added to the ore and heated. The iron oxide combines with the slag and is removed as iron silicate.


FeO + SiO2FeSiO3


Slag


OR


a) NaCN is used as a depressant to separate two different sulfide ores ZnS and PBS in the froth floatation method. It selectively permits PBS to come with froth and prevents ZnS.


Froth Floatation is a method used for the concentration of ores. It is a method used for the separation of gangue materials from sulphide ores. In this method, a suspension of the ore is mixed with pine oil and frothed well. The ore particles get combined with the froth which is collected and dried.


b) Carbon monoxide is used in the Mond process to form a volatile complex of nickel - nickel tetracarbonyl from which nickel is extracted.


Step 1.


Step 2.


c) Coke is used as a reducing agent to reduce zinc oxide to zinc.



The metal is distilled off and cooled quickly.


More from this chapter

All 27 →
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. )

 21

(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

 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.

 24

A metal complex having composition Cr(NH3)4Cl2Br has been isolated in two forms A and B. form A reacts with AgNO3 to give a white precipitate readily soluble in dilute aqueous ammonia whereas B gives a pale yellow precipitate soluble in concentrated ammonia.

(i) Write the formulae of isomers A and B.


(ii) State the hybridization of chromium in each of them.


(iii) Calculate the magnetic moment (spin only value) of the isomer.