Chemical Kinetics for class 11 and 12. For Pre Medical study topic.

1. Chemical Kinetics
By : - Shlok Pushpesh Mathur

2. What is Chemical Kinetics?
 Chemical kinetics, the branch of physical chemistry that is concerned
with understanding the rates of chemical reactions.
 Key Points..
1.Chemical Reaction
2.Rate of Reaction : Factors affecting rate of reaction
3.Activation Energy
4.The half-life
5.Catalysis : Learning about catalysts
6.Chemical Equilibrium
7.Le Châtelier’s Principle

3. Chemical Reaction..
 Chemical reaction, a process in which one or more substances, the
reactants, are converted to one or more different substances, the
products.
Reactant -> Product

4. The Half Life..
 The half-life of a reaction is the time required for the reactant concentration to
decrease to one-half its initial value.

5. Rate of Reaction..
The reaction rate or rate of
reaction is the speed at which
reactants are converted into
products.
For example, the oxidative
rusting of iron under Earth's
atmosphere is a slow reaction
that can take many years, but
the combustion of cellulose in a
fire is a reaction that takes
place in fractions of a second.

6. Factors affecting rate of reaction..
 Temperature
 Pressure
 Concentration
 Surface Area
 Catalyst

7. Effects of Temperature..
Increasing the temperature
increases reaction rates
because of the
disproportionately large
increase in the number of
high energy collisions.

8. Effects of pressure..
Increasing the pressure on a
reaction involving reacting
gases increases the rate of
reaction. Changing the
pressure on a reaction that
involves only solids or liquids
has no effect on the rate. If
you increase the pressure of
a gas, you squeeze it into a
smaller volume.

9. Effects of Concentration..
Increasing the concentration of
reactants generally increases
the rate of reaction because
more of the reacting molecules
or ions are present to form the
reaction products. ... When
concentrations are already high,
a limit is often reached where
increasing the concentration
has little effect on the rate of
reaction.

10. Effects of Surface Area..
Effect of increasing surface area
on the rate of a reaction. ...
Increasing the surface area of a
solid reactant exposes more of
its particles to attack. This
results in an increased chance
of collisions between reactant
particles, so there are more
collisions in any given time and
the rate of reaction increases.

11. Activation Energy..
The Activation Energy (Ea) - is the
energy level that the reactant
molecules must overcome before a
reaction can occur.
In order to calculate the activation
energy we need an equation that
relates the rate constant of a
reaction with the temperature
(energy) of the system. This equation
is called the Arrhenius Equation:

12. Catalyst..
 A catalyst is an agent or
compound that is added to a
process to make a chemical
reaction happen more quickly.
 Types :
Heterogenous
homogenous
Catalysis..
 Catalysis is the process of
increasing the rate of a
chemical reaction by adding a
substance known as a catalyst,
which is not consumed in the
catalyzed reaction and can
continue to act repeatedly.

13. Effects of catalyst on Rate of Reaction..
Catalyst and activation energy..
 To increase the rate of a reaction you
need to increase the number of
successful collisions. One possible way
of doing this is to provide an
alternative way for the reaction to
happen which has a lower activation
energy.
 Adding a catalyst has exactly this effect
of shifting the activation energy. A
catalyst provides an alternative route
for the reaction. That alternative route
has a lower activation energy.

14. Chemical Equilibrium..
Homogenous Equilibrium
Heterogenous Equilibrium

15. Le Châtelier’s Principle..
A principle stating that “if a
constraint (such as a change
in pressure, temperature, or
concentration of a reactant)
is applied to a system in
equilibrium, the equilibrium
will shift so as to tend to
counteract the effect of the
constraint.”

16. Thank you..
Doubt ??