Chemical equilibrium
Effect of pressure or volume on equilibrium
In reaction mixtures containing at least a gaseous compound, changes in the volume of the
system also change the pressure
Boyle's law states: the pressure exerted by a gas (with a given mass at a constant temperature)
is inversely proportional to its volume.
As a result, a decrease in volume leads to increased pressure and vice versa. The pressure of a
system is proportional to the number of gas particles in it. The more gas particles in the system,
the higher the pressure. Again, Le Chaterlier's principle is our guide in predicting how an
equilibrium changes in response to changes in the pressure or volume of the system. Following
a difference in the pressure of the equilibrium mixture, the equilibrium position will shift to
oppose the change.
Example:
We'll use the Haber process again as an example: N2(g) + 3H2(g) ⇌ 2NH3(g)
If the system's volume decreases or the pressure increases, the equilibrium will change to
oppose this change and reduce the pressure. So, in the Haber process, the equilibrium
position will shift right towards the products with fewer gas particles. This would
help reduce the pressure in the system and oppose the change.
On the other hand, if the volume is increased or the pressure is decreased, the equilibrium
position will shift left towards the reactants (N2 + 3H2) since they have more gas
particles on this side compared to the products side. The shift would increase the number of
reactant particles and the pressure to oppose the change.
Effect of catalyst on equilibrium
A catalyst is a material that can be introduced to a reaction to speed it up while not being
consumed in the process. Catalysts often do this by offering a different pathway for the reaction
that requires less activation energy.
Effect of pressure or volume on equilibrium
In reaction mixtures containing at least a gaseous compound, changes in the volume of the
system also change the pressure
Boyle's law states: the pressure exerted by a gas (with a given mass at a constant temperature)
is inversely proportional to its volume.
As a result, a decrease in volume leads to increased pressure and vice versa. The pressure of a
system is proportional to the number of gas particles in it. The more gas particles in the system,
the higher the pressure. Again, Le Chaterlier's principle is our guide in predicting how an
equilibrium changes in response to changes in the pressure or volume of the system. Following
a difference in the pressure of the equilibrium mixture, the equilibrium position will shift to
oppose the change.
Example:
We'll use the Haber process again as an example: N2(g) + 3H2(g) ⇌ 2NH3(g)
If the system's volume decreases or the pressure increases, the equilibrium will change to
oppose this change and reduce the pressure. So, in the Haber process, the equilibrium
position will shift right towards the products with fewer gas particles. This would
help reduce the pressure in the system and oppose the change.
On the other hand, if the volume is increased or the pressure is decreased, the equilibrium
position will shift left towards the reactants (N2 + 3H2) since they have more gas
particles on this side compared to the products side. The shift would increase the number of
reactant particles and the pressure to oppose the change.
Effect of catalyst on equilibrium
A catalyst is a material that can be introduced to a reaction to speed it up while not being
consumed in the process. Catalysts often do this by offering a different pathway for the reaction
that requires less activation energy.
