1Thanks
Q1) Why do we say
ΔS = QrevT
Q2) While finding direction of spontaneity for a reaction, we say
ΔSsurroundings = QsurroundingT = -QsystemT
ΔSsurroundings = -ΔHsystemT
ΔSuniverse = ΔSsystem-ΔHsystemT
and further we express as ΔG=ΔH-TΔS
My question: Why not ΔSsystem = ΔHsystemT ?
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4 Answers
49It can be proved for any reversible process that,
\oint_{.}^{.}{\frac{dq_{rev}}{T}}=0
Thus, we can say that the function qrevT is path independent..
Thus, we can call it state function.. named it entropy...
Entropy is DEFINED as qrev/T and thus it is qrev and nothing else..
49we generally consider the surrounding to be much much much bigger than the system..
thus irrespective of the heat exchange we consider the temperature of the surrounding to be constant...
thus the entropy change is q/T
for the system there is chance of temperature during the course of process.. thus the entropy change is ∫dq//T
11The ans. is very simple....
Srev.= qrev./T we generally consider By convention heat exchange is occuring from the surrounding to the body because the surrounding is very very very big than the system.... hence.....work done by the surrounding isothermally is negetive...and hence equals to -H/T
I think u hav understood.... :)