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Question : 37
Total: 37
(a) A first order reaction is 25 % 4 0 80 %
(b) Define order of reaction. Write the condition under which a bimolecular reaction follows first order kinetics.
OR
(a) A first order reaction is50 % 300 K 1 0 3 2 0 ( E a )
( R = 8.314 J K − 1 mol − 1 )
(b) Write the two conditions for collisions to be effective collisions.
(c) How order of reaction and molecularity differ towards a complex reaction?
[Given :log 2 = 0.3010 , log 3 = 0.4771 , log 4 = 0.6021 , log 5 = 0.6991 ]
(b) Define order of reaction. Write the condition under which a bimolecular reaction follows first order kinetics.
OR
(a) A first order reaction is
(b) Write the two conditions for collisions to be effective collisions.
(c) How order of reaction and molecularity differ towards a complex reaction?
[Given :
Solution:
(a) t =
log
(i)40 min =
log
(ii)t =
log
Dividing (i) by (ii)
=
log
∕
log
=
=
=
t =
= 223.712 min .
k =
log
=
log
=
( log 4 − log 3 )
=
( 0.6021 − 0.4771 )
=
× 0.125 = 0.007196
= 7.196 × 10 − 3 min − 1
(b) Order of reaction: The sum of the coefficients of the reacting species that are involved in the rate equation for the reaction, is called order of reaction.
The condition under which a bimolecular reaction follows first order kinetics is when one of the reactants is taken in large excess that its concentration changes hardly.
OR
(a) At300 K , t 1 ∕ 2 = 30 min
t 1 ∕ 2 =
or k =
k 1 =
= 0.0231 min − 1
At320 K , t 1 ∕ 2 = 10 min
t 1 ∕ 2 =
or k =
k 2 =
= 0.0693 min − 1
According to Arrhenius equation:
log
=
[
−
]
= log
=
[
]
= log
=
[
]
[ ∵ R = 8.314 JK − 1 mol − 1 ]
= log 3 =
E a =
=
= 43848.5 J mol − 1 = 43.85 kJ mol − 1
(b) Two conditions for collisions to be effective collision are :
(i) The reactant molecules must have attained sufficient energy to break chemical bonds
(ii) The reactant molecules must have the proper orientation.
(c) The number of the reacting species that collide simultaneously in a chemical reaction is called as molecularity of a reaction. The sum of the coefficients of the reacting species is the order of reaction.
For complex reactions, molecularity has no significance while the order of reaction is applicable.
(i)
(ii)
Dividing (i) by (ii)
(b) Order of reaction: The sum of the coefficients of the reacting species that are involved in the rate equation for the reaction, is called order of reaction.
The condition under which a bimolecular reaction follows first order kinetics is when one of the reactants is taken in large excess that its concentration changes hardly.
OR
(a) At
At
According to Arrhenius equation:
(b) Two conditions for collisions to be effective collision are :
(i) The reactant molecules must have attained sufficient energy to break chemical bonds
(ii) The reactant molecules must have the proper orientation.
(c) The number of the reacting species that collide simultaneously in a chemical reaction is called as molecularity of a reaction. The sum of the coefficients of the reacting species is the order of reaction.
For complex reactions, molecularity has no significance while the order of reaction is applicable.
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