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Change of entropy

  • Thread starter Petar Mali
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I would like to find change of entropy of composite of two ideal gases which have sane tenperature and preasure and different volumes [tex]V_1[/tex] and [tex]V_2[/tex].

I think about this and I have idea but I'm not sure am I right?

Equation of state of ideal gas is

[tex]PV=RT[/tex]

And we have

[tex]Tds=C_VdT+PdV[/tex]

[tex]P=\frac{RT}{V}[/tex]

[tex]dS=C_V\frac{dT}{T}+RT\frac{dV}{V}[/tex]

First term is equal to zero!

[tex]dS=RT\frac{dV}{V}[/tex]

I think now that change of entropy is

[tex]S=\int^V_{V_1}RT\frac{dV}{V}+\int^V_{V_2}RT\frac{dV}{V}[/tex]

This is change of entropy! Am I right?

Can I use that

[tex]V=V_1+V_2[/tex] ?
 

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