So from the first law for a closed system,(adsbygoogle = window.adsbygoogle || []).push({});

dU=dQ-dW=dQ-PdV

From the second law,

dS=dQ/T + Sgenerated (i.e. the entropy generated)

Putting expression of dQ from second law into first law,

dU=T*dS-T*Sgen-PdV

If s and v are constant,

dU= -T*Sgen>0

Hence dU<0

This is a derivation that was given in class

My questions are as follows:1. When we say s is constant, does it mean there is not heat flow into/out of the system?

2.If dU<0, does the temperature decrease? I find it hard to understand how there can be a positive Sgen and decrease in temperature/ internal energy simultaneously!

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# Entropy generation in chemical reactions

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