Now, in terms of spontaneity, we can say that a galvanic cell uses spontaneous redox reactions to produce and discharge electricity. So Galvanic cells again are batteries. Now here they can make electricity. Discharging means that the electron, the energy that we've made, the electricity that we've made, we start to use it and that means we're discharging it.

Now here we're going to say all spontaneous reactions have a positive standard cell potential value. So here we're going to talk about galvanic cells. They use spontaneous redox reactions and how does that relate to our different variables? We're also going to talk about what happens when we're at equilibrium. So the variables we're going to look at here are changes in your standard Gibbs free energy, changes in your standard entropy total, so energy of the universe, our equilibrium constant K, equilibrium constant versus our reaction quotient Q, and of course our standard cell potential.

We already said that galvanic cells use spontaneous redox reactions and that all spontaneous redox reactions have a positive standard cell potential. So that means that this would have to be greater than 0. We also talked about these other variables in other chapters. For it to be spontaneous, the change in your standard Gibbs free energy has to be less than 0. The change in your standard total entropy has to be greater than 0, your equilibrium constant K has to be greater than one. And then if we're talking about K versus Q here, we'd have to say that our equilibrium constant K would have to be greater than Q.

Now what happens if our galvanic cell makes all this electricity and decides to use it, to use all of it? It's completely discharged all of its electricity. Well, in that case, what happens when you use all the electricity of a battery? It goes dead. But in chemistry, we don't like to say dead, we like to say that it's reached equilibrium. So at equilibrium, our galvanic cell has used up all of its electricity that's produced. So in essence, it's a dead battery.

Here, that would just mean that each of these variables are equal to these same values. So change in standard Gibbs free energy is equal to 0. Change in my standard entropy total is equal to 0, your equilibrium constant K is equal to 1, K is equal to Q, and your standard cell potential is equal to 0. So just remember, a galvanic cell represents a spontaneous electrochemical cell because it utilizes spontaneous redox reactions. If it were to use all of the electricity that it's produced, it would reach equilibrium where this is true for each one of these variables.