# Reversibility of ideal gas processes (isobaric and adiabatic processes)

In an isobaric process, how is it possible to be reversible. In the case that volume is decreased, lets say $2m^3$ to $1m^3$ (at infinitesimally small increments) at a constant $1$ MPa of pressure.

Heat must be extracted such that pressure does not increase in the system. There is a net transfer of heat, so why is it that this process is reversible?

Also in an adiabatic process, with a compression of $2m^3$ to $1m^3$ at a varying pressure. From the idea of adiabatic processes there is no transfer of heat.

So why can an irreversible adiabatic process exist(in an ideal system)?

• "Heat must be extracted such that pressure does not increase in the system." what if the temperature just increased Commented May 13, 2018 at 7:40
• Who says that an isobaric reversible adiabatic compression of an ideal gas is possible? Let me guss. You are trying to determine the entropy change for an adiabatic irreversible compression of an ideal gas that took place at constant externally applied pressure, correct? Commented May 13, 2018 at 12:06