Now recall that a standard subpotential value that's greater than 0 means the reaction is spontaneous. And when it comes to electrochemical cells, remember we have two types. We have our galvanic voltaic cell. Remember galvanic voltage? They're synonymous with each other. You can use them interchangeably. And then we have our electrolytic cell. These are our two typical types of electrochemical cells.
Now for galvanic voltaic cell, we're going to see that the cathode is the half cell compartment that has the higher standard reduction potential and then the anode is the one that has the lower standard reduction potential. This results in a standard cell potential that is greater than 0. So this makes sense here because the galvanic voltage cell is a spontaneous electrochemical cell, so we'd expect it to have a cell potential greater than 0.
The electrolytic cell, on the other hand, everything is kind of reversed here. Here the cathode is now the one with the lower standard reduction potential, and then the anode is the one with the higher standard reduction potential. But remember, your standard cell potential is still cathode minus anode. Because of this, the standard cell potential here will be less than 0.
So just remember, if we know the type of electrochemical cell that kind of guides us into what our standard cell potential should be at the end. And that's based on should the cathode have a higher or lower standard reduction potential or should it be the anode? Knowing this is key to getting the right answer at the end, so keep this in mind when looking at the two types of electrochemical cells.