INTRODUCTION
What is chemical Equilibrium?
Chemical equilibrium refers to the
state of a system in which the
concentration of the reactant and the
concentration of the products do not
change with time and the system does
not display any further change in
properties
When the rate of the forward reaction
is equal to the rate of the reverse
reaction, the state of chemical
equilibrium is achieved by the system.
When there is no further change in the
concentrations of the reactants and the
products due to the equal rates of the
forward and reverse reactions, the
system is said to be in a state of
dynamic equilibrium.
A graph with the concentration on the
y-axis and time on the x-axis can be
plotted. Once the concentration of
both the reactants and the products
stops showing change, chemical
equilibrium is achieved.
Name : Yuvraj Yadav
Study : XI – B
Chemistry
Project
File
ACKNOWLEDGEMENT
I would like to express my special
thanks of gratitude to my chemistry
teacher as well as our principal who
gave me the golden opportunity to do
this wonderful project on the topic
(Write the topic name), which also
helped me in doing a lot of Research
and i came to know about so many new
things I am really thankful to them.
Secondly i would also like to thank my
parents and friends who helped me a lot
in finalizing this project within the
limited time frame.
Why is Chemical
Equilibrium called
Dynamic Equilibrium?
The stage at which the rate of the
forward reaction is equal to the rate of
backward reaction is called an
equilibrium stage. At this point, the
number of reactant molecules
converting into products and product
molecules into reactants are the same.
The same equilibrium can be carried
out with the same reactants anywhere
with similar conditions with Cntinuous
interchanging of molecules hence
chemical equilibrium is dynamic.
Types of Chemical
Equilibrium
There are two types of chemical
equilibrium:
Homogeneous Equilibrium
Heterogeneous Equilibrium
Homogenous Chemical
Equilibrium
In this type, the reactants and the
products of chemical equilibrium are all
in the same phase. Homogenous
equilibrium can be further divided into
two types: Reactions in which the
number of molecules of the products is
equal to the number of molecules of
the reactants. For example,
H2 (g) + I2 (g) ⇌ 2HI (g)
N2 (g) + O2 (g) ⇌ 2NO (g)
Reactions in which the number of
molecules of the products is not equal
to the total number of reactant
molecules. For example,
2SO2 (g) + O2 (g) ⇌ 2SO3 (g)
COCl2 (g) ⇌ CO (g) + Cl2 (g)
Heterogeneous Chemical
Equilibrium
In this type, the reactants and the
products of chemical equilibrium are
present in different phases. A few
examples of heterogeneous
equilibrium are listed below.
CO2 (g) + C (s) ⇌ 2CO (g)
CaCO3 (s) ⇌ CaO (s) + CO2 (g)
Thus, the different types of chemical
equilibrium are based on the phase of
the reactants and products.
⇒ Check: Ionic Equilibrium
Factors Affecting
Chemical Equilibrium
According to Le-Chatelier’s principle, if
there is any change in the factors
affecting the equilibrium conditions,
the system will counteract or reduce
the effect of the overall trnsformation.
This principle applies to both chemical
and physical equilibrium.
There are several factors like
temperature ,pressure and
concentration of the system which
affect equilibrium. Some important
factors affecting chemical equilibrium
are discussed below
CHANGE IN CONCENTRATION:
The concentration of the reactants
or products added is relieved by the
reaction which consumes the
substance which is added.
The concentration of reactants or
products removed is relieved by the
reaction which is in the direction
that replenishes the substance
which is removed.
When the concentration of the
reactant or product is changed,
there is a change in the composition
of the mixture in chemical
equilibrium.
Change in Pressure:
Change in pressure happens due to the
change in the volume. If there is a
change in pressure it can affect the
gaseous reaction as the total number
of gaseous reactants and products are
now different. According to Le
Chatelier’s principle, in heterogeneous
chemical equilibrium, the change of
pressure in both liquids and solids can
be ignored because the volume is
independent of pressure.
Change in Temperature:
The effect of temperature on chemical
equilibrium depends upon the sign of
ΔH of the reaction and follows Le-
Chatelier’s Principle.
As temperature increases the
equilibrium constant of an
exothermic reaction decreases.
In an endothermic reaction the
equilibrium constant increases with
an increase in temperature.
Along with the equilibrium constant,
the rate of reaction is also affected by
the change in temperature. As per Le
Chatelier’s principle, the equilibrium
shifts towards the reactant side when
the temperature increases in case of
exothermic reactions, for endothermic
reactions the equilibrium shifts
towards the product side with an
increase in temperature.
Effect of a Catalyst:
A catalyst does not affect the chemical
equilibrium. It only speeds up a
reaction. In fact, catalyst equally
speeds up the forward as well as the
reverse reaction. This results in the
reaction reaching its equilibrium faster.
The same amount of reactants and
products will be present at equilibrium
in a catalysed or a non-catalysed
reaction. The presence of a catalyst
only facilitates the reaction to proceed
through a lower-energy transition state
of reactants to products.
Effect of Addition of an Inert
Gas:
When an inert gas like argon is added
to a constant volume it does not take
part in the reaction so the equilibrium
remains undisturbed. If the gas added
is a reactant or product involved in the
reaction then the reaction quotient will
change.
Examples of Chemical
Equilibrium
In chemical reactions, reactants are
converted into products by the forward
reaction and the products may be
converted into reactants by the
backward reaction. The two states,
reactants and products are different in
composition.
After some time of the start of the
reaction, the rate of the forward and
the backward reactions may become
equal. After this, the number of
reactants converted will be formed
again by the reverse reaction such that
the concentration of reactants and
products do not change anymore.
Hence, the reactants and products are
in chemical equilibrium.
N2O4 ⇌ 2NO2
PCl5 ⇌ PCl3 +PCl2
N2 + H2 ⇌ 2NH3
Importance of Chemical
Equilibrium
It is useful in many industrial processes
like,
Preparation of ammonia by
Haber’s process: In this nitrogen
combines with hydrogen to form
ammonia, the yield of ammonia is
more at low temperature, high
pressure and in the presence of iron
as catalyst.
Preparation of sulphuric acid by
contacts process: In this process,
the fundamental reaction is the
oxidation of sulphur dioxide into
sulphur trioxide. This involves
chemical equilibrium.
Problems on Chemical
Equilibrium
1. The equilibrium constant KP for the
reaction N2 (g) + 3H2 (g) ⇌ 2NH3 (g) is
1.6 × 10-4 atm-2 at 400oC. What will
be the equilibrium constant of the
Chemical equilibrium at 500oC if the
heat of the reaction at this
temperature range is -25.14 kcal?
Solution:
Equilibrium constants at different
temperature and heat of the reaction
are related by the equation,
log KP2 = -25140/2.303 × 2 [773 – 673 /
773 × 673] + log 1.64 × 10-4
log KP2 = -4.835
KP2 = 1.462 × 10-5 atm-2
2. Given the equation, N2 (g) + 3H2
(aq) ⇌ 2NH3 (g), Find Q and determine
which direction the reaction will shift
in order to reach the state of chemical
equilibrium.
Solution:
Given, [N2] = 0.04M, [H2] = 0.09M, and
K = 0.040
Since only nitrogen and hydrogen
concentration is given, it can be
assumed as the reactants and
ammonia as the product. Since
ammonia concentration is not given it
can be assumed to be zero.
As q is the ratio of the relative
concentration of products to reactants,
here Q =0.
Since K = 0.04 is larger than Q, nitrogen
and hydrogen will combine to form
product ammonia.
BIBLIOGRAPHY
FOR MAKING THIS PROJECT I HAVE
TAKEN HELP FROM THE FOLLOWING :-
WWW.WIKIPEDIA.COM
WWW.GOOGLE.COM
WWW.BYJUS.COM
BALAJI ICSE TEXTBOOK
