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Back Chemical Chemical Engineering Dictionary Thermodynamics State and Equilibrium - Types of Equilibrium - Thermal, Mechanical, Phase, Chemical

State and Equilibrium - Types of Equilibrium - Thermal, Mechanical, Phase, Chemical


Thermodynamic studies the system with equilibrium stage Equilibrium means that the system is balance i.e no unbalance force is within the system. An equilibrium system does not undergo any change since it is isolated from its surroundings.


  1. Thermal Equilibrium
  2. Mechanical Equilibrium
  3. Phase Equilibrium
  4. Chemical Equilibrium

Thermal Equilibrium

The system is said to be in thermal equilibrium when there is no temperature difference throughout the entire system

Mechanical Equilibrium

This equilibrium is concerned with pressure of the system.i.e there is no change of pressure throughout the system with time. Although pressure may vary within the system because of gravitational force. in most thermodynamic system the changes of pressure because of gravitational effect is very small therefore it is ignored.

Phase equilibrium

In this type of equilibrium there are two phases involved. When the mass of one phase reaches an equilibrium level and stays there then the system is said to be in phase equilibrium

Chemical Equilibrium

The two phase system after achieving their phase equilibrium, if their chemical composition also remain constant and does not change with time then is said to be in chemical equilibrium

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