[Bob Sacamano]

Is there any case in which a non-spontaneous reaction will occur? For example, if two chemicals are added to a beaker and are allowed to reach equilibrium, are both reactions occurring as the reaction shifts to equilibrium?

[Schrödinger]

Is there any case in which a non-spontaneous reaction will occur?

Spontaneity of many reactions depend on temperature. What is spontaneous at 500K may not be spontaneous at 300K. So, if possible, changing the temperature could cause a non-spontaneous reaction to occur.

if two chemicals are added to a beaker and are allowed to reach equilibrium, are both reactions occurring as the reaction shifts to equilibrium?

Chemical equilibrium is dynamic.

[MrTeo]

Is there any case in which a non-spontaneous reaction will occur?

Spontaneity of many reactions depend on temperature. What is spontaneous at 500K may not be spontaneous at 300K. So, if possible, changing the temperature could cause a non-spontaneous reaction to occur.

Another example could be the electrolysis of water, which is obviously non-spontaneous at standard conditions and occurs thanks to the work done by the electric source:

H₂O→H₂+½O₂

Moreover if you consider Maxwell-Boltzmann's distribution of speeds you can see that there's always a certain amount of particles which have the energy needed to start the reaction but their contribution to the whole progress of the process is completely irrelevant:



We could say that the reaction has got a very small K, and raising or lowering the temperature we can change significantly its value: