CBSE Class-12 Chemistry Quick Revision Notes
Chapter-04: Chemical Kinetics
• Chemical kinetics:
It is the branch of chemistry that deals with the study of reaction rates and their
mechanisms.
• Rate of reaction:
It is the change in concentration of reactant (or product) in unit time.
• The unit of rate of reaction is mol L-1s-1.
• A+B→C+D
− d [ A]
Rate of disappearance of A =
dt
where d[A] is small change in conc. of ‘A’ and dt is small interval of time
−d[ B]
Rate of disappearance of B =
dt
Where d[B] is small change in conc. of ‘B’ and dt is small interval of time
+ d [C ]
Rate of appearance of C =
dt
Where d[C] is small change in conc. of ‘C’ and dt is small interval of time
+ d[ D]
Rate of appearance of D =
dt
Where d[D] is small change in conc. of ‘D’ and dt is small interval of time
− d [ A] − d [ B ] + d [C ] + d [ D ]
Rate = = = =
dt dt dt dt
• Rate law or rate equation:
It is the expression which relates the rate of reaction with concentration of the reactants.
The constant of proportionality ‘k’ is known as rate constant.
• Average rate:
It is the rate of reaction measured over a long time interval.
∆x
Average rate =
∆t
where is Δx change in concentration and Δt is large interval of time.
• Instantaneous rate:
It is the rate of reaction when the average rate is taken over a particular moment of time.
dx
Instantaneous rate = .
dt
where dx is small change in conc. and dt is the smallest interval of time.
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Chapter-04: Chemical Kinetics
• Chemical kinetics:
It is the branch of chemistry that deals with the study of reaction rates and their
mechanisms.
• Rate of reaction:
It is the change in concentration of reactant (or product) in unit time.
• The unit of rate of reaction is mol L-1s-1.
• A+B→C+D
− d [ A]
Rate of disappearance of A =
dt
where d[A] is small change in conc. of ‘A’ and dt is small interval of time
−d[ B]
Rate of disappearance of B =
dt
Where d[B] is small change in conc. of ‘B’ and dt is small interval of time
+ d [C ]
Rate of appearance of C =
dt
Where d[C] is small change in conc. of ‘C’ and dt is small interval of time
+ d[ D]
Rate of appearance of D =
dt
Where d[D] is small change in conc. of ‘D’ and dt is small interval of time
− d [ A] − d [ B ] + d [C ] + d [ D ]
Rate = = = =
dt dt dt dt
• Rate law or rate equation:
It is the expression which relates the rate of reaction with concentration of the reactants.
The constant of proportionality ‘k’ is known as rate constant.
• Average rate:
It is the rate of reaction measured over a long time interval.
∆x
Average rate =
∆t
where is Δx change in concentration and Δt is large interval of time.
• Instantaneous rate:
It is the rate of reaction when the average rate is taken over a particular moment of time.
dx
Instantaneous rate = .
dt
where dx is small change in conc. and dt is the smallest interval of time.
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