
What is Helmholtz free energy and Gibbs free energy?
Answer
431.7k+ views
Hint: Thermodynamic potentials: It is a scalar quantity which represents the thermodynamic state of a system. These are the functions of thermodynamic variables pressure, volume, temperature, and entropy.
Complete answer:
Helmholtz free energy: It is a thermodynamic potential in which the work is measured when the system is closed and volume and temperature of the system is constant.
It can be represented from the following equation:
where,
Helmholtz free energy
Internal energy
Temperature
Entropy
Derivative form of Helmholtz free energy in terms of thermodynamic potential can be represented as follows:
Hence it can be written as function of volume and temperature as
Application of Helmholtz free energy:
Specific heat at constant pressure can be determined as follows:
Gibbs free energy: It is a thermodynamic potential in which the maximum reversible work is measured when pressure and temperature of the system is constant.
It can be represented from the following equation:
where,
Gibbs free energy
Enthalpy
Temperature
Entropy
Derivative form of Gibbs free energy in terms of thermodynamic potential can be represented as follows:
Hence it can be written as function of pressure and temperature as
Application of Gibbs free energy:
Can be used to determine spontaneity of the reaction.
Specific heat at constant pressure can be determined as follows:
Note:
Helmholtz energy is sometimes represented with the symbol ‘A’, so need not to get confused. For finding relations between thermodynamic potentials and energies, a thermodynamic square method should be used.
Complete answer:
Helmholtz free energy: It is a thermodynamic potential in which the work is measured when the system is closed and volume and temperature of the system is constant.
It can be represented from the following equation:
where,
Derivative form of Helmholtz free energy in terms of thermodynamic potential can be represented as follows:
Hence it can be written as function of volume and temperature as
Application of Helmholtz free energy:
Specific heat at constant pressure can be determined as follows:
Gibbs free energy: It is a thermodynamic potential in which the maximum reversible work is measured when pressure and temperature of the system is constant.
It can be represented from the following equation:
where,
Derivative form of Gibbs free energy in terms of thermodynamic potential can be represented as follows:
Hence it can be written as function of pressure and temperature as
Application of Gibbs free energy:
Can be used to determine spontaneity of the reaction.
Specific heat at constant pressure can be determined as follows:
Note:
Helmholtz energy is sometimes represented with the symbol ‘A’, so need not to get confused. For finding relations between thermodynamic potentials and energies, a thermodynamic square method should be used.
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