Discussion :: Chemical Engineering Thermodynamics
- A change in state involving a decrease in entropy can be spontaneous, only if
|
A.
It is exothermic |
|
B.
It is isenthalpic |
|
C.
It takes place isothermally |
|
D.
It takes place at constant volume |
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Answer : Option A
Explanation :
From second law of thermodynamics
$$\eqalign{ & TdS \geqslant \delta Q \cr & \Rightarrow TdS \geqslant dU + \partial W \cr} $$
For an irreversible process $$TdS \geqslant dU + \partial W > 0$$
So, the entropy will be greater than zero for an spontaneous(irreversible ) process only when the internal energy and work done are zero so, for an exothermic reaction since the internal energy is not zero we can say the entropy need not be greater than zero.
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