Solution of Surface Chemistry Test Paper - 03 (Class 12, CBSE) Class 12 Notes | EduRev

Class 12 : Solution of Surface Chemistry Test Paper - 03 (Class 12, CBSE) Class 12 Notes | EduRev

 Page 1


CBSE TEST PAPER-03 
CLASS - XII CHEMISTRY (Surface chemistry) 
Topic: Hetrogeneous catalysis, zeolites, enzyme catalysis 
ANSWERS 
Ans 1. According to modern theory of catalysis, the mechanism of heterogeneous catalysis 
involves following steps –  
(i)       Diffusion of reactants on the surface of catalyst. 
(ii)      Adsorption of reactant molecules on the surface. 
(iii)  Occurrence of reaction on the catalysts surface through formation of an 
intermediate. 
(iv)    Desorption of products from surface. 
(v)     Diffusion of products away from surface. 
Ans 2. Activity of a catalyst is the extent to which a catalyst can increase the rate of reaction. 
It depends upon the strength of chemisorption. 
Selectivity of a catalyst is its ability to direct a reaction to yield a particular product. 
The action of a catalyst is highly selective in nature.  
Ans 3. The catalytic reaction that depends upon the pore structure of the catalyst and the size 
of the reactant and product molecules is called shape selective catalysis. Zeolites are 
good shape catalysts due to there honeycomb – like structure. The reactions taking 
place in zeolites depends upon the size and the shape of reactant and product 
molecules as well as upon the pores and cavities of the zeolites.   
Ans 4. Examples of enzyme- catalysed reactions are – 
(1) Inversion of cane sugar: 
12 22 11 2 6 12 6 6 12 6
( ) H O( )  C H O (aq) + C H O (aq)
Invertase
C H O aq + --- - ? l
2. Decomposition of urea into ammonia and carbon dioxide.
2 2 2 3 2
( ) ( )  2NH (g)  +CO (g)
Urease
NH CONH aq H O + --- ? l
Ans 5.  The characteristics of enzyme catalysed reactions are – 
(1) They are highly efficient and specific in nature. 
(2)  They have maximum activity under specific temperature and pH. 
(3)  Their activity increases on adding activators and coenzymes while decreases in 
the presence of poison or inhibitors. 
Page 2


CBSE TEST PAPER-03 
CLASS - XII CHEMISTRY (Surface chemistry) 
Topic: Hetrogeneous catalysis, zeolites, enzyme catalysis 
ANSWERS 
Ans 1. According to modern theory of catalysis, the mechanism of heterogeneous catalysis 
involves following steps –  
(i)       Diffusion of reactants on the surface of catalyst. 
(ii)      Adsorption of reactant molecules on the surface. 
(iii)  Occurrence of reaction on the catalysts surface through formation of an 
intermediate. 
(iv)    Desorption of products from surface. 
(v)     Diffusion of products away from surface. 
Ans 2. Activity of a catalyst is the extent to which a catalyst can increase the rate of reaction. 
It depends upon the strength of chemisorption. 
Selectivity of a catalyst is its ability to direct a reaction to yield a particular product. 
The action of a catalyst is highly selective in nature.  
Ans 3. The catalytic reaction that depends upon the pore structure of the catalyst and the size 
of the reactant and product molecules is called shape selective catalysis. Zeolites are 
good shape catalysts due to there honeycomb – like structure. The reactions taking 
place in zeolites depends upon the size and the shape of reactant and product 
molecules as well as upon the pores and cavities of the zeolites.   
Ans 4. Examples of enzyme- catalysed reactions are – 
(1) Inversion of cane sugar: 
12 22 11 2 6 12 6 6 12 6
( ) H O( )  C H O (aq) + C H O (aq)
Invertase
C H O aq + --- - ? l
2. Decomposition of urea into ammonia and carbon dioxide.
2 2 2 3 2
( ) ( )  2NH (g)  +CO (g)
Urease
NH CONH aq H O + --- ? l
Ans 5.  The characteristics of enzyme catalysed reactions are – 
(1) They are highly efficient and specific in nature. 
(2)  They have maximum activity under specific temperature and pH. 
(3)  Their activity increases on adding activators and coenzymes while decreases in 
the presence of poison or inhibitors. 
Ans 6. Mechanism of enzyme catalysed reactions- 
There are active centres or cavities on the surface of enzyme particles. The molecules 
of the reaction or substrate which have complementary shape fit into these just like a 
key   
fits into a lock. This forms an activated complex which decomposes to yield products. 
The reactions proceed in two steps –  
Step 1:  Binding of enzymes to substrate to form activated complex. 
      E+S   -----  ES 
Step 2 :  Decomposition of complex to form products. 
 ES -----  E + P. 
Ans 7.  Process      Catalyst 
1. Haber’s process for preparation of ammonia. Iron , Molybdenum 
2. Ostwald’s process for manufacture of nitric acid. Platinised asbestos. 
3. Contact process for manufacture of sulphuric acid.     Vanadium pentaoxide (V 2O 5).
Ans 8. The metal ions like Na
+
, Mn
2+
, Co
2+
, Cu
2+
 etc. can bind weakly to enzyme molecules. 
This increases their catalytic activity and therefore metal ions can act as activators. 
Ans 9. The optimum temperature is 298K – 310K and optimum pH is 5 – 7 for enzyme – 
catalysed reactions. 
Ans 10. Example of zeolite catalysed reactions are: 
(a) Cracking of hydrocarbons in petroleum industries. 
(b) Conversion of alcohols into gasoline. 
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