Hello, "Reversible processes are at equilibrium : Driving force is only infinitesimally greater than the opposing force Process occurs in a series of infinitesimal steps, and at each step the system in at equilibrium with the surroundings It would take an infinite amount of time to carry out. However Irreversible Process are not at equilibrium; thus a spontaneous process" http://www.columbia.edu/itc/chemistry/environmental/lectures/Ch_13.pdf page 4. During irreversible chemical reaction, the reaction is happening in one direction. My question is does the reaction is also happening in the second direction but at lower rate? Or it depends (Some of chemical reaction can occur in both directions but at different rate however others can only occur in one direction like combustion)? Thanks.