change in entropy for adiabatic systems

[Estefania Lima 2G]

Since q=0 in an adiabatic system, is the entropy of an adiabatic system constant?
Thanks

[Albert Chong_1L]

Factors other than heat flow (q) can affect entropy. For example, if volume was increased for a gas, there would be more entropy since the gas molecules have more possible micro states in which to exist.

[Chem_Mod]

For reversible adiabatic process, delta S should be 0.

[Albert Chong_1L]

For reversible adiabatic process, delta S should be 0.

I can see that is true through deltaS=q/T, since deltaS will be 0 when q is 0.

However, if V2/V1 can be substituted for T2/T1 in the equation deltaS=nCln(T2/T1), then how does this equation show deltaS as 0 when q=0 (adiabatic)?

Is this equation only for free expansion in which entropy increases despite no change in internal energy?

[Chem_Mod]

PV=nRT does not work for adiabatic process. It is in fact which is not covered in this class. For free expansion, delta S=nRln(V2/V1) due to the statistical model you have been shown in class (derived from delta S=nRln(W2/W1)