Entropy vs Enthalpy – Difference [Explained with Pdf]

One of the differentiating point for Entropy vs Enthalpy is that the entropy is a measure of the randomness of molecules while the enthalpy is the total energy associated with the system.

Before knowing the entropy and enthalpy difference, let’s know briefly about them.

What is Enthalpy?

Enthalpy for the thermodynamic system is the sum of the internal energy and the product of pressure and volume.

Enthalpy is denoted by the symbol ‘H’ and Mathematically it is given by,

H = U + Pv

The enthalpy gives the total energy of the system. The unit of the enthalpy in the SI system is Joule (J) and in the FPS system is Btu.

What is Entropy?

Entropy is known as the measure of the disorder or randomness of molecules in the system.

The entropy is the extensive property and is denoted by the symbol ‘S’. The change in entropy of the system is given by the ratio of heat transfer to the absolute temperature.

Mathematically, change in entropy is given by,

`\Delta S = \frac{\Delta Q}{T}`

The unit of the change in entropy in the SI system is Joules/Kelvin (J/K) and in the FPS system is BTU/°F

Difference between enthalpy and entropy:

Sr. No.EnthalpyEntropy
1]The enthalpy of the system is given by the sum of internal energy and the product of pressure and volume.The term entropy is known as the measure of the randomness of molecules.
2]The enthalpy is denoted by the symbol h.The entropy is denoted by the symbol S.
3]It is used to describe enthalpy at a particular state or change in enthalpy for the process.It is used as the change in entropy for the particular process.
4]The enthalpy is given by, H = U + PV.The change in entropy is given by, ΔS = ΔQ/T.
5]The unit of the enthalpy is Joule (J).The unit of change in entropy is J/K.
6]It is easy to calculate enthalpy at state.It is difficult to calculate entropy for a particular state.
7]The enthalpy is related to the first law of thermodynamics.The entropy is related to the second law of thermodynamics.
8]The system prefers minimum enthalpy.The system prefers maximum entropy.
9]The change in enthalpy for the system is positive for the endothermic process and negative for the exothermic process.The change in entropy is positive for the spontaneous process and negative for the non-spontaneous process.
10]The process with no enthalpy change is known as the isenthalpic process.The process with no entropy change is known as the isentropic process.
These are the points that differentiate the entropy and enthalpy.

FAQ’s:

  1. What is difference between entropy and enthalpy?

    The enthalpy and entropy can be compared as the enthalpy is the total energy of the system while the entropy is the measure of randomness or disorder of the molecules in the system.

  2. What is the relation between enthalpy and entropy?

    The change in the entropy is the change in enthalpy per average absolute temperature.

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