Q14 of 26 Page 1

(a) Write the principle of vapour phase refining.

(b) What is the role of depressant in froth floatation process?


(c) Write the name of reducing agent to obtain iron from Fe2O3 at high temperature.


(a) The principle of vapor phase refining is that the impure metal should form a volatile compound with an available reagent and compound formed should be easily decomposable.


(b) In froth floatation, depressant is added to separate 2 sulphide ores. In case the ore contains PbS or ZnS the depressant used is NaCN which prevents ZnS from coming to surface by forming a complex with it.



(c) The name of reducing agent to obtain iron from Fe2O3 at high temperature is carbon monoxide (CO).


Fe2O3 is reduced to Fe in steps as follows-


3 Fe2O3 + CO 2 Fe3O4 + CO2


Fe3O4 + CO 3FeO + CO2


FeO +CO Fe + CO2


More from this chapter

All 26 →
12

Define the following terms with an example in each:

(a) Lyophobic colloids


(b) Homogeneous catalysis


(c) O/W emulsion


OR


Write three differences between Physisorption and Chemisorption.


 13

A solution of glucose (Molar mass = 180 g mol–1) in water has a boiling point of 100.20°C. Calculate the freezing point of the same solution. Molal constants for water Kf and Kb are 1.86 K kg mol–1 and 0.512 K kg mol–1 respectively.

 15

(a) What is the radius of sodium atom if it crystallizes in bcc structure with the cell edge of 400 pm ?

(b) Examine the given defective crystal:



(i) Write the term used for this type of defect.


(ii) What is the result when XY crystal is doped with divalent (Z2+) impurity?


 16

Give reasons:

(a) Propanone is less reactive than ethanal towards nucleophilic addition reactions.


(b) O2N–CH2–COOH has lower pKa value than CH3COOH.


(c) (CH3)2CH–CHO undergoes aldol condensation whereas (CH3)3C–CHO does not.