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What is the difference between zero,1st,2nd,3rd order reaction?

Dear Student,

An overview of first , second and third order reaction.

Third order reaction is one in which sum of power of the concentration of reactants in the rate law expression is equal to 3.

For a reaction the order of the reaction is the number of particles that react in slowest step of the reaction which is the rate determining step. Reaction takes place when all the reacting particles come together and collide, the collision provides the activation energy for reaction to take place. Possibility of 3 particles to collide together is less thus the third order reactions are uncommon. 

Example of few third order reactions are..

  • 2NO +O2  ---> 2NO2
  • 2NO + Cl2 ---> 2NOCl2
  • 2F2Cl3 + SnCl4 ---> 2FeCl2

 Rate  = k [A]3


Regards

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A reaction is zero order if its rate is independent of the concentration of reactants or a zero order reaction means that the rate of reaction is proportional to zero power of the concentration of reactants. For a zero order reaction of the form R à P
The rate of reaction , rate = – d [R] / dt = k [R]0
As any quantity raised to power zero is unity
Rate = – d [R] / dt = k x 1
d[R] = – kdt
Integrating both sides, we get
[R] = – kt + I
where, I is the constant of integration
At t = 0, [R] = [R]0, where [R]0 is initial concentration of reactant.
Substituting this value in equation (20.4), we get
[R] = – kt + [R]0 or kt = [R]0 – [R]
K = 1 / t [ [R]0 – [R]]
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