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KINETICS OF FIRST ORDER REACTIONS:

A chemical reaction is said to be of first order reaction if its rate is determined by the change of one of the concentration term only.
Consider a general chemical reaction its follow first order kinetics
Let [A] 0 =initial concentration of reactant A
[A]t = concentration of after time t
[B]t = concentration of product B after time t
On Integration of above equation
On rearrangement equation (1) give equation of straight line



We can also write equation (1)   as  
Case (1): 

On increasing angle (slop) the value of reaction constant increases hence k3>k2> k1

Case (2):    


       
Case (3):   
           
Case (4):           
[A]t/[A]0  Vs  t :


 Variation o f concentration with time:
Characteristic of 1st order:
(1) Concentration of reactant left after regular time interval of time will constitute a geometrical progression (GP).
(2) A first order reaction takes infinite time for completion.
(3) All radioactive disintegrations are examples of first order reaction
(4) Decomposing of H2O2 , Ester and Inversion of sugar are examples of first order reactions
(5) Half life time of first order reaction does not depend upon initial concentration.

Similarly concentration of product B after time t 

Graph show increase in concentration  of [B] and [A] both as exponential manner.

Half life time of first Order reaction:
Natural life time of first order reaction   

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