Answer:
Spontaneous processes are characterized by the overall conversion of order to disorder.
Explanation:
The second law of thermodynamics states that: A spontaneous process occurs only if there is an increase in entropy of a system and its surroundings.
Entropy, S, is a measure of the randomness or disorder of a system. It is measured in J/Kmol.
The change in entropy, ∆S = ∆H/T
Where ∆H = change in enthalpy, T = Temperature in Kelvin.
For,
I. An endothermic reaction, ∆S = positive (that is, ∆S is greater than zero), there is an increase in entropy, therefore, the reaction is spontaneous.
II. An exothermic reaction, ∆S = negative (that is, ∆S is less than zero) there is a decrease in entropy, so, the reaction is non-spontaneous.
III. A system at equilibrium, ∆S = 0.
Then,
The standard change in entropy of a reaction, ∆So reaction , is the difference in the standard entropies between products and reactants:
∆So reaction = n ∆Soproducts - m ∆Soreactants
Where, = sigma = sum of,
∆ = delta = change in,
n and m = stoichiometric coefficients of the products and reactants respectively.
Furthermore, the entropy of the system and surroundings is referred to as the entropy of the universe.
∆Suniverse = ∆Ssurroundings + ∆Ssystem.
Processes leading to an increase in entropy include melting, heating, vaporization, dissolving.
