Coulometry

the different types of electrochemical cells that exist can be connected to the idea of spontaneity. Whether an electrochemical cell is spontaneous or not helps us to categorize them and split them into two different camps here, we're going to say in terms of spontaneity, the following correlations between the following variables can be made. So here we have gibbs, free energy under standard conditions. Um That's what this little circle here means. Standard conditions being 25 degrees Celsius, where your ph is equal to seven, where your concentration is equal to one polarity. We also have K, which is our equilibrium constant. We have our cell potential, we have delta S, which is our entropy and then we have Q versus K. Q. Is our reaction quotient. It's used as a way to determine are we at equilibrium or not? From these variables, we can determine the type of reaction classification we have meaning. Is it spontaneous? Non spontaneous or at equilibrium? And from that we can determine what type of electrochemical cell we have. So if we take a look at the first row, when delta, G is less than zero, that means that K will be greater than one. Your cell potential be greater than zero. Delta. As in here, this is delta as total or delta s. universe. Based on the second law of thermodynamics, our Q will be um less than K. Now in this part. This helps us determine direction if you set up a number line and K is here in the middle and Q is less than it, then Q is always gonna shift in the direction to get to KR equilibrium constant. So our reaction would shift in the forward direction. All of these variables are telling me one thing that my reaction is spontaneous and when we have a spontaneous reaction, that means our electrochemical cell is a galvanic Orville take cell next. If we reverse the order of all the signs where adults, G. Is greater than zero, K. Is less than one. Your cell potentials less than zero as well as your entropy of your universe is less than zero. Here, Q would be greater than K. So here we move in the reverse direction in terms of our chemical reaction. So here this would mean that our reaction is non spontaneous and when you have a non spontaneous reaction, that means your electrochemical cell is an electrolytic cell, we'll talk a bit more about electrolytic cells down below, but just realize your electrolytic cells represent non spontaneous electrochemical cells. Then finally, when everything is equal to their given value, this means that we are at equilibrium. And when an electrical cell is at equilibrium, that means it represents a dead battery, it is discharged all its electricity or it's consumed all the electricity. Therefore it is at a state of equilibrium. Now we said that an electrochemical cell represents a non spontaneous electrochemical cell here because it's non spontaneous, it requires outside energy source to work. So here requires a battery. And so because it requires a battery, it consumes electricity. Remember of galvanic or voltaic cell produces or discharges electricity, electrolytic one consumes electricity. Here we have an example of basic electrolytic cell here, we have the implementation of a battery in order to drive electrons from one side to the other side. And in this case this side will be positive and this side here will be negative. In fact, now here are positive electrode will actually be the anodes. So remember for galvanic or voltaic cell, the node was negative now because we're dealing with an electrolytic cell, it's positive. And now the cathode is negative. If we think about it, it doesn't make too much sense for negative electrons to want to travel to a negative electrode like charges, repel each other. That's why we require a battery. The battery is there to force the reaction to occur because it because it's not a natural process here. The electron affinity, if we're talking in terms of this uh image here, we'd say that the electron affinity for the cathode would be low, electrons do not want to go to the negative cathode and then the ionization energy for the anodes would be low as what would be high, it would take a lot of energy to remove the negative electrons from the animal. They just don't want to leave the an ode to go to a negative electrode. So basically things are reversed in terms of a galvanic cell versus an electrolytic cell. The only common thing. the thing that's always consistent is that the anodes still undergoes oxidation and the Catholics still undergoes reduction. The problem here, though, is it's not a natural process because negative electrons again don't want to go to something with the same charge that it has. That's why batteries required to force this reaction to happen. So this is the common feature of both types of electrochemical cells, whether they're spontaneous or non spontaneous and always undergoes oxidation, whereas the catholic always undergoes reduction. So just remember the differences between an electrolytic cell versus a galvanic slash will take cell and remember the different variables when you look at them in conjunction with one another. Help to determine if a chemical reaction is spontaneous, non spontaneous or add equilibrium.