Prove that in a reversible process:
∆(system) + ∆S(surroundings) = 0
Or
Prove that there is no net change in entropy in a reversible process.
What do you understand by:
(i) The entropy of fusion?
(ii) The entropy of vapourisation ?
You are given normal boiling points and standard enthalpies of vapourisation. Calculate the entropy of vapourisation of liquids listed below:
Liquid
Calculate the entropy change of n-hexane when 1 mole of it evaporates at 341.7 K(∆Hvap = 29.0 kJ mol–1).
What are the two tendencies which determine the feasibility of process? How are the two related to each other?
The following two tendencies are responsible for determining the feasibility of a process:
(i) The tendency of a system to acquire a state of minimum energy i.e. energy factor. It is expressed in terms of enthalpy change (∆H). A negative value of ∆H suggests that system has the tendency to proceed.
(ii) The tendency of a system to acquire a state of maximum randomness i.e. randomness factor. It is expressed by T∆S where T is the absolute temperature and ∆S is the change in entropy. A positive value of T∆S indicates an inherent tendency of a process to occur.
Relation between two tendencies:
The overall tendency or the driving force of a process is expressed in terms of free energy change (∆G). This is expressed as ∆G = ∆H – T∆S
This equation is called Gibb’s Helmholtz equation. For a spontaneous process, ∆G should have a negative value i.e. the system should undergo a decrease in its free energy.