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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