Process such as isobaric, isochoric, quasistatic, adiabatic

[cos(e)]

Just say an ideal gas goes through process such as isobaric, isochoric, quasistatic, adiabatic etc, is there any special cases where entropy is conserved, or am i thinking enthalpy. Also how is enthalpy found in adiabatic processes?

 

[Mapes]

Total entropy is conserved in reversible processes. System entropy is conserved in reversible processes without heat flow (reversible work doesn't carry entropy).

For an ideal gas, enthalpy $H$ is $nc_PT+H_0$, so for any process $\Delta H=nc_P\Delta T$.

 

[cos(e)]

do we use delta H= n*Cp* delta T even when the pressure is not constant?

What do u mean by reversible process, i havnt learned that yet :S

 

[Mapes]

do we use delta H= n*Cp* delta T even when the pressure is not constant?

For an ideal gas; it's a special case.

What do u mean by reversible process, i havnt learned that yet :S

A reversible process is an idealization in which no gradients exist in temperature, pressure, or any intensive properties. It's not realizable in real life, where the only way to transfer energy is by differences in temperature, pressure, etc. But if we assume the differences are small enough to be negligible, it makes the calculations easier precisely because we can assume that entropy generation is zero. More http://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)" .