Reversible vs irreversible process

[Eli Pazol 2F]

Can someone explain the difference between a reversible and irreversible process?

[MelanieAu1G]

In an irreversible reaction, the reactants convert to products, but the products cannot convert back to reactants (think of combustion, in which oxygen gas is burned with a compound; this process cannot be reverted/ reversed).
In a reversible reaction the reactants and products are never fully consumed; they are each constantly reacting and being produced (think of this as a reaction at equilibrium, in which the reaction does not stop, but conversions/reactions do not appear to be taking place because the products and reactants are forming at equal rates). Reversible reactions can occur, for example, when a system is at equilibrium and pressure(external) = pressure(internal); essentially when a system is at equilibrium.

[Paul_Ajodha_2K]

Building off of what Melanie said, if you were to theoretically be in a state of equilibrium between the pressure of a gas in a system with that of the external pressure. An infinitesimally small change in external pressure will change the the pressure in the inside in such a way that it can literally be reversed with the same infinitesimal change in the opposite direction. However, with an irreversible process, the differing pressures are large enough quantities that an extremely small change in pressure inside the gas or outside wouldn't change the state of the system. The bottom line is that reversible processes are considered the "better" of the two in the sense that you get more work out a system that undergoes a reversible process.