General Chemistry
Chapter 3: Chemical Equilibrium
,Chemical equilibrium
Reversible reaction
A + B → C + D (forward reaction);
Some examples of Reversible re
A + B ← C + D (backward reaction)
PCl5(g) PCl3 (g) +
A + B C + D
H2(g) + I2(g) 2 HI(g)
• A chemical reaction which can go in the
forward direction and backward direction
N2O4(g) 2 NO2(g)
simultaneously is called a reversible reaction
CaCO3(s) CaO (s) + CO2(g
Irreversible reactions:
• That proceeds in one direction only. Like,
precipitation reaction , neutralization
reaction
,Nature of chemical equilibrium:
• Let a chemical reaction between
H2O(g) and CO(g) in a closed
vessel,represented as:
H2O(g) + CO(g) H2 (g) + CO2(g)
• At certain time, the system attains a
state of equilibrium in which two Fig: The changes in concentrations with time for
opposing reactions proceed equally
• Thus, chemical equilibrium may be
defined as the state of a reversible
in which the rates of the forward
and reverse reactions are equal and Forward reaction rate equals
reaction rate
the concentrations of the reactants
and products remain constant.
Fig: Reaction at equilibrium
, Characteristics of Chemical Equilibrium
• Cannot be attained in an Open Vessel
• Dynamic in nature (in constant motion)
• Reversible and attains equilibrium state spontaneously
• Can be approached from either side.
• Represents a compromise between opposing tendencies.
• A catalyst cannot change the equilibrium point
• Constancy of concentrations
The Equilibrium Constant:
Let a general reaction
aA + bB cC + dD
Where, molar concentration (active mass) of A, B, C and D at the equilibrium
be represented as, [A], [B], [C] and [D]
Chapter 3: Chemical Equilibrium
,Chemical equilibrium
Reversible reaction
A + B → C + D (forward reaction);
Some examples of Reversible re
A + B ← C + D (backward reaction)
PCl5(g) PCl3 (g) +
A + B C + D
H2(g) + I2(g) 2 HI(g)
• A chemical reaction which can go in the
forward direction and backward direction
N2O4(g) 2 NO2(g)
simultaneously is called a reversible reaction
CaCO3(s) CaO (s) + CO2(g
Irreversible reactions:
• That proceeds in one direction only. Like,
precipitation reaction , neutralization
reaction
,Nature of chemical equilibrium:
• Let a chemical reaction between
H2O(g) and CO(g) in a closed
vessel,represented as:
H2O(g) + CO(g) H2 (g) + CO2(g)
• At certain time, the system attains a
state of equilibrium in which two Fig: The changes in concentrations with time for
opposing reactions proceed equally
• Thus, chemical equilibrium may be
defined as the state of a reversible
in which the rates of the forward
and reverse reactions are equal and Forward reaction rate equals
reaction rate
the concentrations of the reactants
and products remain constant.
Fig: Reaction at equilibrium
, Characteristics of Chemical Equilibrium
• Cannot be attained in an Open Vessel
• Dynamic in nature (in constant motion)
• Reversible and attains equilibrium state spontaneously
• Can be approached from either side.
• Represents a compromise between opposing tendencies.
• A catalyst cannot change the equilibrium point
• Constancy of concentrations
The Equilibrium Constant:
Let a general reaction
aA + bB cC + dD
Where, molar concentration (active mass) of A, B, C and D at the equilibrium
be represented as, [A], [B], [C] and [D]
