Reversible And Irreversible Processes

As discussed in NCERT Class 11, Chapter 12 (Thermodynamics), a reversible process is an idealised process carried out infinitely slowly through a continuous succession of equilibrium states, so it can be exactly retraced. An irreversible process, by contrast, occurs rapidly and passes through non-equilibrium states. When a balloon bursts, the gas undergoes a sudden free expansion into the atmosphere, with turbulence and pressure gradients that are far from equilibrium, so it cannot be reversed by traversing the same states; this makes it strongly irreversible. The option calling it reversible is wrong because the gas will never spontaneously rush back into the balloon. The option calling it isothermal is wrong because a rapid expansion need not occur at constant temperature, and free expansion of a real gas can change temperature. The option labelling it adiabatic and reversible is contradictory: while a fast burst may be approximately adiabatic, the presence of dissipation and non-equilibrium states makes it irreversible. A consistency check: all natural spontaneous processes that increase disorder, like a bursting balloon, are irreversible, in agreement with the second law's direction of entropy increase.