Chemical Thermodynamics Question 56
Question: Considering entropy (S) as a thermodynamic parameter, the criterion for the spontaneity of any process is [CBSE PMT 2004]
Options:
A) $ \Delta S_{system}>0 $ only
B) $ \Delta S_{surroundings}>0 $ only
C) $ \Delta S_{system}+\Delta S_{surroundings}>0 $
D) $ \Delta S_{system}-\Delta S_{surroundings}>0 $
Show Answer
Answer:
Correct Answer: C
Solution:
$ \Delta S_{system}+\Delta S_{surroundings}>O $ (for spontaneity)
Because of $ \Delta S=R\ln \frac{V_2}{V_1} $ Here the volume of gas increase from $ V_1 $ to $ V_2 $ at constant temperature T.
The total increase in entropy of the system and its surrounding during the spontaneous process of expansion considered above is, thus $ R,\ln ,( \frac{V_2}{V_1} ) $ since $ V_2>V_1 $ it is obvious that the spontaneous (irreversible) isothermal expansion of a gas is accompanied by an increase in the entropy of the system and its surrounding considered together.
$ \Delta S_{system}+\Delta S_{surroundings}>0 $ .
