Types of Equilibrium Involved in Physical and Chemical Processes

Physical equilibrium is defined as the state of balance that arises between two or more phases or physical qualities of the same substance.

Physical Equilibrium is a state of being in which everything is in balance.

In equilibrium, if the opposing processes are characterised solely by physical changes, the equilibrium is referred to as physical equilibrium. For example, with the evaporation of water, equilibrium between water and vapour exists.

            Water ⇋ Vapour 

Chemical Equilibrium is a state of equilibrium in a chemical reaction.

When opposing processes in an equilibrium result in chemical changes, the equilibrium is referred to as chemical equilibrium. Consider the equilibrium between acetic acid, water, and acetate, as well as the equilibrium between acetic acid and hydronium ions.

Types of Equilibrium Involved in Physical Processes

Equilibrium types that are involved in a physical process

In terms of physical balance, there are three different types:

• Phase Equilibrium
• Equilibrium between a solution and a solid
• Equilibrium between gases and liquids

Phase Equilibrium

At 0°C, the number of water molecules that turn into ice equals the number of water molecules that turn into liquid water when ice melts. 

Exactly the same rate at which water freezes and ice melts, there is no difference between the two. A state of equilibrium has been achieved between solid ice and flowing water as a result of this.

    Ice (s) ⇌ Water (l)

Whenever a closed system is present, the rate of liquid water evaporation equals or exceeds the rate of water vapour condensation (or vice versa).

A state of equilibrium exists between the liquid phase and the vapour phase in which it is encircled.

 A state of equilibrium exists between the liquid phase and the vapour phase in which it is encircled.

Water (l) ⇌ Water (g)

Equilibrium Between a Solution and a Solid

When a solute in a saturated solution comes into contact with an undissolved solute, it is well known that the number of molecules leaving the solution (depositing) equals the number of molecules dissolving from the solid. Therefore, the solute in solution has reached equilibrium with the solid that has not been dissolved.

The solute (aq) is the same as the solute (s)

Equilibrium Between Gases and Liquids

Gases that do not react with liquids may dissolve in a liquid at a rate that is proportional to the pressure within the liquid. In a closed container, there is a state of equilibrium between the gas contained within the liquid and the gas present above and around the container. 

In soft drinks, for example, the carbon dioxide gas contained within the liquid is in balance with the gas contained within the container’s empty space.

     Gas (solution) ⇌ Gas (g)

Types of Chemical Equilibrium 

It is possible to classify chemical equilibrium into two categories:

• Homogeneous equilibrium
•  Heterogeneous equilibrium

Homogeneous Equilibrium

• In this sort of chemical equilibrium, the reactants and products of chemical equilibrium are all in the same phase at the same time.
•  It is possible to further differentiate homogeneous equilibrium into two types:
•  A reaction where the number of molecules in the products equals the number of molecules in the reactants is known as a one-to-one match.

Heterogeneous Equilibrium

In this sort of chemical equilibrium, the reactants and products of chemical equilibrium are present in distinct phases of the reaction. 

Factors Affecting Chemical Equilibrium

There are a variety of parameters that influence equilibrium, including the temperature, pressure, and concentration of the system.

• Concentration shifts
• Change in the amount of pressure
• Increase or decrease in temperature
•  Change in the equilibrium constant. 
• Catalysts 
•  Addition of Inert Gas 

According to Le Chatelier’s principle, as the temperature of an exothermic reaction rises, the equilibrium changes towards the reactant side.

Meanwhile, when the temperature of an endothermic reaction rises, the equilibrium shifts towards the product side.

Conclusion

Physical equilibrium is defined as the development of equilibrium between two or more phases or physical qualities that are wholly distinct from one another. There is no change in the chemical composition of the material during these procedures. A similar substance can exist in two different physical states, which is represented by this symbol. 

In chemistry, equilibrium refers to the state of a system in which both the concentration of the reactant and, consequently, the concentration of the product do not fluctuate with time, and the system does not exhibit any change in attributes from one point in time to the next.

When the rate of the forward reaction is equal to the rate of the reverse reaction, the system has reached a state of chemical equilibrium, which is defined as the absence of any net reaction.