Answer 1

Conditions for spontaneous and non-spontaneous reactions in terms of free energy
change:
 a. For a spontaneous process, ∆G < 0 means the Gibbs energy of the system decreases
during the process. The end of the spontaneous process is equilibrium which
corresponds to minimum in G.
 b. Hence the change in Gibbs energy, ∆G must be zero for the process at equilibrium.
Thus if,
 a. ∆G < 0, the process is spontaneous.
 b. ∆G > 0, the process is non-spontaneous.
 c. ∆G = 0, the process is at equilibrium.

Definition of entropy: The property of a system which measures the degree of disorder or randomness in the system is called entropy. It is denoted by letter S.