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Thursday, July 4, 2019

Difference between Enthalpy and Entropy

Enthalpy
  • Enthalpy is a thermodynamic property.
  • It is a measure of the total heat content of the system.
  • It is equal to the sum of internal energy and the flow energy( that is the product of pressure and volume).
  • It is denoted by ' H'
H = U + PV
  • The unit of enthalpy is Joules (J), Calories (C)
  • The enthalpy of the system increases when energy is added or decreases when energy is given off)
Entropy
  • Entropy is a measure of the randomness or disorder of a system.
  • In other words, it is called as it is a measure of that portion of the total energy of a system which is unavailable to do useful work.
  • It is denoted by ' S '
  • It is a state function ( as the change in entropy depends on the initial and final states of the system and not on the path followed by the system) and extensive properties of the system.
  • The change in entropy of a system is the integral of the reversible heats divided by the absolute temperature, over the reversible path.
  • Where 'rev' indicates that dQ/T  is calculated along a reversible path only.
  • The unit of entropy is Joules/Kelvin (J/K)

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