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 1^st 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.

First Order Parallel Rreactions

Half life time of first Order reaction:

Natural life time of first order reaction: