PPT: Chemical Kinetics | Chemistry for JEE Main & Advanced PDF Download

 Page 1


• The branch of chemistry, which deals with the
study of reaction rates and their mechanisms,
called chemical kinetics.
• Thermodynamics tells only about the feasibility
of a reaction whereas chemical kinetics tells
about the rate of a reaction.
• For example, thermodynamic data indicate that
diamond shall convert to graphite but in reality
the conversion rate is so slow that the change is
not perceptible at all.
2
Page 2


• The branch of chemistry, which deals with the
study of reaction rates and their mechanisms,
called chemical kinetics.
• Thermodynamics tells only about the feasibility
of a reaction whereas chemical kinetics tells
about the rate of a reaction.
• For example, thermodynamic data indicate that
diamond shall convert to graphite but in reality
the conversion rate is so slow that the change is
not perceptible at all.
2
• Kinetic studies not only help us to determine
the speed or rate of a chemical reaction but
also describe the conditions by which the
reaction rates can be altered.
• The factors such as concentration,
temperature, pressure and catalyst affect the
rate of a reaction.
3
Page 3


• The branch of chemistry, which deals with the
study of reaction rates and their mechanisms,
called chemical kinetics.
• Thermodynamics tells only about the feasibility
of a reaction whereas chemical kinetics tells
about the rate of a reaction.
• For example, thermodynamic data indicate that
diamond shall convert to graphite but in reality
the conversion rate is so slow that the change is
not perceptible at all.
2
• Kinetic studies not only help us to determine
the speed or rate of a chemical reaction but
also describe the conditions by which the
reaction rates can be altered.
• The factors such as concentration,
temperature, pressure and catalyst affect the
rate of a reaction.
3
• The speed of a reaction or the rate of a
reaction can be defined as the change in
concentration of a reactant or product in unit
time. It can be expressed in terms of:
• (i) the rate of decrease in concentration of
any one of the reactants, or
• (ii) the rate of increase in concentration of
any one of the products.
4
Page 4


• The branch of chemistry, which deals with the
study of reaction rates and their mechanisms,
called chemical kinetics.
• Thermodynamics tells only about the feasibility
of a reaction whereas chemical kinetics tells
about the rate of a reaction.
• For example, thermodynamic data indicate that
diamond shall convert to graphite but in reality
the conversion rate is so slow that the change is
not perceptible at all.
2
• Kinetic studies not only help us to determine
the speed or rate of a chemical reaction but
also describe the conditions by which the
reaction rates can be altered.
• The factors such as concentration,
temperature, pressure and catalyst affect the
rate of a reaction.
3
• The speed of a reaction or the rate of a
reaction can be defined as the change in
concentration of a reactant or product in unit
time. It can be expressed in terms of:
• (i) the rate of decrease in concentration of
any one of the reactants, or
• (ii) the rate of increase in concentration of
any one of the products.
4
Consider a hypothetical reaction, assuming that the volume of 
the   system remains constant
R ? P
One mole of the reactant R produces one mole of the product 
P. If  [R]1 and [P]1 are the concentrations of R and  respectively 
at time t1and [R]2 and [P]2 are their concentrations at time t2 
then,
?t = t2 – t1
?[R] = [R]2 – [R]1 ? [P] = [P]2 – [P]1
&
The square brackets in the above expressions are used to express molar 
concentration.
5
Page 5


• The branch of chemistry, which deals with the
study of reaction rates and their mechanisms,
called chemical kinetics.
• Thermodynamics tells only about the feasibility
of a reaction whereas chemical kinetics tells
about the rate of a reaction.
• For example, thermodynamic data indicate that
diamond shall convert to graphite but in reality
the conversion rate is so slow that the change is
not perceptible at all.
2
• Kinetic studies not only help us to determine
the speed or rate of a chemical reaction but
also describe the conditions by which the
reaction rates can be altered.
• The factors such as concentration,
temperature, pressure and catalyst affect the
rate of a reaction.
3
• The speed of a reaction or the rate of a
reaction can be defined as the change in
concentration of a reactant or product in unit
time. It can be expressed in terms of:
• (i) the rate of decrease in concentration of
any one of the reactants, or
• (ii) the rate of increase in concentration of
any one of the products.
4
Consider a hypothetical reaction, assuming that the volume of 
the   system remains constant
R ? P
One mole of the reactant R produces one mole of the product 
P. If  [R]1 and [P]1 are the concentrations of R and  respectively 
at time t1and [R]2 and [P]2 are their concentrations at time t2 
then,
?t = t2 – t1
?[R] = [R]2 – [R]1 ? [P] = [P]2 – [P]1
&
The square brackets in the above expressions are used to express molar 
concentration.
5
• Rate of disappearance of R
= Decrease in concentration of R = - ? [R]
Time taken ?t
Rate of appearance of P
=   Increase in concentration of P = + ? [P]
Time taken                               ? t
Since, ?[R] is a negative quantity (as concentration of reactants is
decreasing), it is multiplied with –1 to make the rate of the reaction a
positive quantity.
6