Characteristics of entropy:
1. Entropy is a thermodynamic state function that is a measure of the randomness or disorderliness of the system.
2. In general, the entropy of gaseous system is greater than liquids and greater than solids. The symbol of entropy is S.
3. Entropy is defined as for a reversible change taking place at a constant temperature (T), the change in entropy (∆S) of the system is equal to heat energy absorbed or evolved (q) by the system divided by the constant temperature (T).
ΔSsys = qrev / T
4. If heat is absorbed, then AS is positive and there will be increase in entropy. If heat is evolved, ∆S is negative and there is a decrease in entropy.
5. The change in entropy of a process represented by AS and is given by the equation, ∆Hsys = Sf – Si
6. If Sf > Si , ∆S is positive, the reaction is spontaneous and reversible. If Sf < Si , ∆S is negative, the reaction is non-spontaneous and irreversible.
7. Unit of entropy: SI unit of entropy is J K‘.
