Which of the following is the correct expression of ΔS for an isobaric process?
So, what is the first thing which comes to our mind?
Yes, Isobaric ⇒ constant pressure
Now, as we have already seen that
Entropy change in an isobaric process (at constant pressure)
dS = dqrev(P)T also dqrev(P) = dH
But dH=CPdT, substituting for relationship with entropy,
Integrating both sides
ΔS=Cp[ln T]T2T1=Cp lnT2T1
ΔS=2.303Cp logT2T1=ΔS=Cp lnT2T1
For n moles:
ΔS=nCPln T2T1=2.303nCPlog T2T1