Reversible and Irreversible [ENDORSED]

[Maya Johnson 2a]

How can I tell the difference between reversible and irreversible in questions we are given?

[Chem_Mod]

Usually the question will state reversible or irreversible.

But here are additional comments that likely suggest one or the other:

Question states slow or fast change.
Slow is reversible.
Fast is irreversible.

Equilibrium pathway is a reversible pathway.
Non-Equilibrium pathway is irreversible.

Pressure inside and outside are different, then it is irreversible.

Temperature changes along the pathway, then it is irreversible.

Pressure inside and outside are same, then it is reversible.

Temperature constant along the pathway, then it is reversible.

I think I mention all of these in class.

[Tanya Bearson 2K]

If a reaction is occurring in an open beaker can you assume it is reversible because the pressure inside and outside the beaker will be constant? Likewise, can you assume that reactions in closed beakers will be irreversible?

[Chem_Mod]

If a reaction is occurring in an open beaker can you assume it is reversible because the pressure inside and outside the beaker will be constant? Likewise, can you assume that reactions in closed beakers will be irreversible?

We covered simple systems changing (ideal gas expanding). For example a small change in volume, dV, when pressure internal and external are essentially equal.
Or a large change in volume, delta V, when pressure internal and external are not equal.

For a chemical reaction to reach equilibrium it needs to occur in a closed system as the reactants and products must be present for the forward and reverse reactions to occur and to reach equilibrium (forward rate = reverse rate).

Open systems don't reach equilibrium because the products escape and the reaction goes to completion with all reactants covered to products.