Chapter 6: Chemical Equilibrium
1. Introduction to Equilibrium
A chemical reaction reachesequilibriumwhen the rates of the
forward and backward reactions become equal.
At equilibrium, the concentration of reactants and products remain
constant, not necessarily equal.
Equilibrium is adynamic state, which means reactions continue but
there is no net change.
2. Characteristics of Chemical Equilibrium
Occurs in aclosed system.
Rate of forward reaction = Rate of backward reaction.
Concentration of reactants and products remain constant.
No visible change at macroscopic level.
3. Types of Equilibrium
Homogeneous Equilibrium:All reactants and products are in the
same phase (e.g., gases or liquids).
Example:N2(g)+3H2(g)⇌2NH3(g)N2(
g
)+3H2(
g
)⇌2NH3(
g
)
Heterogeneous Equilibrium:Reactants and products are in different
phases.
Example:CaCO3(s)⇌CaO(s)+CO2(g)CaCO3(
s
)⇌CaO(
s
)
+CO2(
g
)
4. Law of Chemical Equilibrium
For a general reaction:
aA+bB⇌cC+dD
aA
+
bB
⇌
cC
+
dD
Theequilibrium constantKc
Kc
is given by:
Kc=[C]c[D]d[A]a[B]b
Kc
=[
A
]
a
[
B
]
b
[
C
]
c
[
D
]
d
Square brackets indicate molar concentrations at equilibrium.
