Naming Question [ENDORSED]

[K Stefanescu 2I]

Why is reversible expansion called “reversible”?

[Nina Gautam 1K]

We call it reversible because we are thinking about it as occurring in many small steps (infinitesimally small steps) rather than all at once, which gives us a more accurate work value. Because we are thinking about it in small steps as opposed to all at once, it can hypothetically occur in the opposite direction as well.

[Clarisse Wikstrom 1H]

Can think of a reversible reaction as being at equilibrium?

[Sohini Halder 1G]

The system starts at equilibrium (think Dr. Lavelle's example where both pressures are 1 atm) but an infinitesimally small change happens which starts the reversible process.

[Lily Guo 1D]

Reversible expansion is expansion that occurs as a result of infinitesimally small steps that can push the expansion either forward or backwards with the smallest of changes. This results in a maximum of work being done. In contrast, irreversible expansion is expansion that occurs as result of finite steps, and even if you were to "reverse" the step that resulted in expansion, work wouldn't be entirely conserved. The work done is less than maximum.

[Chem_Mod]

Slight elaboration, you can think of reversible processes being at equilibrium. With a reversible expansion, the external pressure is kept essentially equal to the internal pressure and is only very slowly changed so that both the inside and the outside are constantly in equilibrium. This is of course impossible in real life, but possible in theoretical representations.