How do i calculate the entropy change for an isobaric process, if i know
T1, T2, n and Cv ?
Try looking there.
There is nothing there about entropy change
What is the definition of entropy?
entropy change = dS = int( dQ/T )
where you integrate from state 1, to state 2.
The forumula only holds for reversible processes and i don't know if thats the case in my question.
Correct, you can now use this in conjunction with the information which astrorob provided to calculate the entropy change.
Indeed, the formula does only hold for a reversible process, but it may be useful to note that since entropy is a state function it is independent of the path taken and depends only on the initial and final states. Therefore, for any process, even an irreversible one, we can chose a reversible path between the initial and final states that allows us to calculate the change in entropy.
Does that make sense?
so i shoud insert the value for dQ = nCvdT and by that getting
dS = int( (n Cv dT)/T) = n Cv ( (1/T) dT ) = nCv ln(T2/T1) ?
Is that correct, even though the process is not reversible?
The only thing that concerns me is the Cv. Since the process is isobaric, you need Cp. Apart from that your expression is correct.
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