10th. Chemistry. Ch.9. Exercise Solved (Malik Xufyan) Cell # 0313-7355727

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CHEMISTRY [10TH
]
2020
Chemical equilibrium
Chapter No. 09
Malik Xufyan
J I A S A C A D E M Y – T A N G A W A L A A D D A J H A N G S A D A R P H # 0 3 1 3 7 3 5 5 7 2 7

2. Chapter # 09 : Chemical equilibrium Physics [Part 1]
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Chapter # 9 : Chemical Equilibrium
Exercise Solution
Short Questions answers
Q.1. What are irreversible reactions? Give a few characteristics of them.
Ans.
Irreversible reactions:
The reactions in which the products do not recombine to form reactants are called Irreversible
reactions. These are complete reactions and these are represented by between
reactants and products.
2H2 + O2 2H2O
Characteristics:
a. It is complete reaction.
b. It proceed in one direction.
c. It is represented by single headed arrow . i.e,
d. All reactants are converted into products.
Q.2. Define chemical equilibrium state.
Ans.
Definition: When the rate of the forward reaction takes place at the rate of reverse reaction, the
composition of the reaction mixture remains constant, it is called chemical equilibrium state.
For example:
There two chemical equilibrium states:
I. Static equilibrium state
II. Dynamic equilibrium state.
H2 + I2 2HI
Q.3. Give the characteristics of reversible reactions.
Ans.
Characteristics:
1. These reactions never go to completion.
2. In these reactions, products can recombine to form reactants.
3. These reactions proceed in both direction
4. These are represented by double arrow between reactants and products
5. They consists of forward and reverse reactions.
Q.4. How is dynamic equilibrium state established?
Ans. In a reversible reaction, dynamic equilibrium is established before the completion of
reaction. It is represented graphically in figure. At initial stage the rate of forward reaction is
very fast and reverse reaction is taking place at a negligible rate. But graphically forward
reactions slows down and reverse reaction speeds up. Eventually, but reactions attain the same
rate, it is called a dynamic equilibrium state.
Q.5. Why at equilibrium state reaction does not stop?
Ans. At equilibrium state a reaction does not stop. Because forward and reverse reactions keep
on taking place at the same rate but in opposite reaction
H2 + I2 2HI
Q.6. Why equilibrium state is attainable from either way?

3. Chapter # 09 : Chemical equilibrium
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Ans. An equilibrium sate is attainable from either way because it may start from reactant to give
products while products recombine to give reactant again.
Q.7 What is relationship between active mass and rate of reaction?
Ans. Law of mass action describe the relationship
rate of a reaction.
According to this law:
The rate at which a substance reacts directly proportional to its active mass and the rate of a
reaction directly proportional to the product to the active masses of
Example: A + B
At equilibrium state:
The rate of forward reaction = The rate of reverse reaction
Kc is called equilibrium constant. It is represented as:
Law of Mass Action describes the relationship between
rate of a reaction.
Q.8 Derive equilibrium constant expression for the synthesis of ammonia from nitrogen
and hydrogen.
Ans.
The rate of forward reaction:
The rate of reverse reaction:
Q.9 .Write the equilibrium constant expression for the Following reactions:


Ans. (i) H2(g) + 12(g) -----------> 2H1
The rate of forward reaction Kf= [H
rate of reverse reaction Rr = Kr[H1] The
equilibrium constant expression:
Chemical equilibrium Physics [Part 1]
J I A S A c a d e m y p h # 0 3 1 3 7 3 5 5 7 2 7
is attainable from either way because it may start from reactant to give
products while products recombine to give reactant again.
What is relationship between active mass and rate of reaction?
Ans. Law of mass action describe the relationship between active masses of the reactants and the
The rate at which a substance reacts directly proportional to its active mass and the rate of a
reaction directly proportional to the product to the active masses of the reacting substance,
A + B ------------> C_+D
The rate of forward reaction = The rate of reverse reaction
Kc is called equilibrium constant. It is represented as:
Law of Mass Action describes the relationship between active masses of the reactants and the
Q.8 Derive equilibrium constant expression for the synthesis of ammonia from nitrogen
2NH
The rate of forward reaction:
The rate of reverse reaction:
.Write the equilibrium constant expression for the Following reactions:
H2(g) + I2 ------------> 2H1(g)
CO + 3H2 ------------> CH4(g) + H20(g)
> 2H1(g)
The rate of forward reaction Kf= [H2][12] The
reaction Rr = Kr[H1] The
equilibrium constant expression:
Products
Reactants
[HI]2
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is attainable from either way because it may start from reactant to give
between active masses of the reactants and the
The rate at which a substance reacts directly proportional to its active mass and the rate of a
the reacting substance,
active masses of the reactants and the
Q.8 Derive equilibrium constant expression for the synthesis of ammonia from nitrogen
.Write the equilibrium constant expression for the Following reactions:

4. Chapter # 09 : Chemical equilibrium
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(ii)
The rate of forward reaction
The rate of reverse reaction
The equilibrium constant expression:
Q.10 How direction of a reaction can be predicted?
Ans. Direction of a reaction at particular moment can be predicted by inserting the
concentration of the reactants and products at that particular amount in the equilibrium
expression.
If Qc < Kc the reaction goes from left to
If Qc > Kc the reaction goes from right to left, i.e., in reverse reaction to attainn equilibrium.
If Qc = Kc forward and reverse reactions takes place at equal rates I.e equilibrium has been
established.
Q.11. How can you know that a reaction has achieved an equilibrium state?
Ans. When rate of forward reaction becomes equal to rate of reverse reaction, it will achieve
the equilibrium state.
Rate of forward reaction = rate of reverse reaction
Q.12. What are the characteristics of a reaction that establishes equilibrium state at once?
Ans.
Characteristics:
in this state, rate of forward reaction is equal to rate of reverse reaction.
It may be dynamic or chemical equilibrium state.
Concentration of reactants and concentration of products does not change.
At equilibrium state a reaction does not stop.
Q.13. If reaction quotient Qc of a reaction is more than Kc. What will be the direction of
the reaction?
Ans. If Qc > Kc the reaction goes
Chemical equilibrium Physics [Part 1]
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CH4(g) + H20(g)
The rate of forward reaction
The rate of reverse reaction
The equilibrium constant expression:
a reaction can be predicted?
Ans. Direction of a reaction at particular moment can be predicted by inserting the
concentration of the reactants and products at that particular amount in the equilibrium
If Qc < Kc the reaction goes from left to right, I.e in forward reaction to attain equilibrium.
If Qc > Kc the reaction goes from right to left, i.e., in reverse reaction to attainn equilibrium.
If Qc = Kc forward and reverse reactions takes place at equal rates I.e equilibrium has been
Q.11. How can you know that a reaction has achieved an equilibrium state?
When rate of forward reaction becomes equal to rate of reverse reaction, it will achieve
Rate of forward reaction = rate of reverse reaction
H2 + I2 ⇄ 2HI
Q.12. What are the characteristics of a reaction that establishes equilibrium state at once?
in this state, rate of forward reaction is equal to rate of reverse reaction.
It may be dynamic or chemical equilibrium state.
entration of reactants and concentration of products does not change.
At equilibrium state a reaction does not stop.
Q.13. If reaction quotient Qc of a reaction is more than Kc. What will be the direction of
Ans. If Qc > Kc the reaction goes from right to left, i.e., in reverse reaction to attain equilibrium.
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Ans. Direction of a reaction at particular moment can be predicted by inserting the
concentration of the reactants and products at that particular amount in the equilibrium
right, I.e in forward reaction to attain equilibrium.
If Qc > Kc the reaction goes from right to left, i.e., in reverse reaction to attainn equilibrium.
If Qc = Kc forward and reverse reactions takes place at equal rates I.e equilibrium has been
Q.11. How can you know that a reaction has achieved an equilibrium state?
When rate of forward reaction becomes equal to rate of reverse reaction, it will achieve
Q.12. What are the characteristics of a reaction that establishes equilibrium state at once?
Q.13. If reaction quotient Qc of a reaction is more than Kc. What will be the direction of
from right to left, i.e., in reverse reaction to attain equilibrium.

5. Chapter # 09 : Chemical equilibrium Physics [Part 1]
5 | P a g e J I A S A c a d e m y p h # 0 3 1 3 7 3 5 5 7 2 7
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