Energy Diagram

When talking about thermodynamics and kinetics, one of our best friends is going to be the free energy diagram. So it's gonna be essential that we learn how to interpret thes correctly. The reason free energy diagrams are important is because they're going to serve as a summary of the thermodynamics and kinetics of a reaction. All right, so what I want to do first is relate free energy diagrams to what we've already learned and then learn how to interpret them. All right, so remember that in Chapter one, maybe you guys were able to watch that lesson. Maybe you did it, but it's fine. Remember that Adams save energy by forming bonds. Alright. The entire idea of a chemical bond is it's a shared region of space that they share electrons. And remember that we could use molecular orbital diagrams to really illustrate how much energy we're saving. So remember that we had our atomic orbital's on the sides and we had our molecular orbital's on the top in the bottom. And even if you don't remember this that well, that's okay, because I'm just going to show you that, for example, for a hydrogen atom, remember that a hydrogen atom over here would have one electron. A hydrogen atom over here would have another electron. These air called one s. Because remember that they just fill the one s orbital. All right, this is what they would look like in terms of energy. If they were not bonded to anything, remember that by sharing electrons, though, they could wind up filling their octet and filling their atomic orbital. So we said, was that as you make a bond between these two hydrogen, you're gonna jump down and energy in energy, okay? And that's what this would look like. It would look like this after they're bonded, because now you're saving energy by sharing those electrons. All right? Now, remember that we could also use a graph of the distances to figure out how much energy we're saving as the nuclear. I got closer together. So here, just you guys know this was like the energy state that we had over here. If it was not bonded to anything. And you can see these hydrogen atoms the way that I drew them here, they're not bonded. Okay, But then, as we get them closer together as we get our nuclear closer together. What would eventually happen is that they would form this perfect sweet spot where they would be the perfect distance apart. In this case, it was 1.33 Angstrom. And that would be the amount of distance required to save the max amount of energy. Okay, now, the number of the energy is important. This just happened to be negative for 36 kg per mole. You don't need to memorize that at all. Okay, later on, we're gonna use a chart to figure that out. But what is important is that all this information could be related on the free energy diagram. Okay, so the free energy diagram is basically a storyline of everything that I just said. What it tells us is that this is what the Adams looked like before they were bonded. This was their energy level, all right, After they decided to react, this is what they looked like. And now this is our energy level. Okay, So did we save energy or did we spend energy? Okay, that's really the way we think about it. And in this case, we saved energy, and it's gonna be the same amount that we're talking about over here. Okay, so that's what we do with a free energy diagram. What we're looking at is the X axis is the reaction coordinate saying, as the reaction proceeds, What is this? What are the entities looking like on then? The Y axis is usually gonna be either heat talking about in therapy. Or it's gonna be spontaneity, which is we're gonna talk about in just a second, which is the Delta G. All right, so here, I'm just gonna go ahead and restates, um, stuff free energy diagrams give us information on spontaneity and rate of reactions. All right, And now what does this mean? What it means is that this has to do with thermodynamics and kinetics. Thermal dynamics is what we call spontaneity, and that describes the favorability of a reaction. So when I say that something spontaneous, that means that it's favorable. That means that it wants toe happen by itself. All right. The equation that we used to understand thermal dynamics is gonna be your favorite Gibbs free energy. Okay, we can't get away from this reaction, and I mean from this equation, we're gonna be using it pretty much for most of this chapter. Remember that what it was was that Delta G was equal to Delta H, which is the in therapy minus the temperature times the entropy or the Delta s later on, I'm gonna be going in depth on each of these on each of these variables. But right now, I just know that that's what Delta G is. Its spontaneity. Okay, Delta G is usually related by the difference in energy between the beginning and the end. Okay, so it's usually adult Aggie. Then what's the rate? Or the kinetics? The kinetics has to do with how fast the reaction would take place. If it is favorable. So or even if it's not favorable, how fast with this reaction take place. So there are a lot of very spontaneous reactions in this world that do not happen at measurable rates or are impressionable rates because they're so slow. Okay. And the kinetics has to do with the activation energy that it takes in order to make a reaction go forward. All right, so the activation energy in the graph in the free energy diagram I gave you above would be the difference in the energy between the beginning and your highest point in the reaction. Okay, so this would be my activation energy later on. We're going to describe that better as well. But right now, I just know that it's basically the difference between where you started and the highest point you have to achieve in order to make the reaction go forward. Okay, So what I want to do now is I want to just do some really basic qualitative, um, recognition here. This isn't about I don't want you guys toe calculate anything yet. We're just going to decide. What kind of reactions are we looking at here? Are they gonna be spontaneous? Are they gonna be non spontaneous? Are they gonna happen fast? Are they gonna happen? Slow. Okay, So what I want you guys to do is go ahead and look at the following four reactions and try to figure out if it's spontaneous or not. And if the rate is gonna happen quickly or slowly or fast or slow, and then I'll go ahead and answer these for you. All right, So let's go

So for this first problem, what we're gonna be looking at right away is if we're gonna be releasing energy or spending energy to make this direction go forward. So we want to do is you wanna look at the energy level of our beginning re agents and then the energy level of our products, and we want to say, Okay, is the energy going down, which means that I'm releasing. Okay, that's also gonna be a negative value of Delta G. Or is the energy going up at the end? Which means I'm spending energy, and that's gonna be a positive value. Okay, so in this case, it's going to be the negative value, right? I'm releasing. Okay. Well, there's actually a word for that. There's a word for when you're releasing energy or when. Overall, you have a negative value of Delta G, and that's called X organic. Okay, so when I say ex organic, that means that I am basically getting some energy back or releasing some energy into the system after the reaction takes place. Okay. Do you guys remember the name of if I'm spending energy? Yeah, that would be undergone IQ. Okay. That means that it's taking. I'm having to put energy into the system to make it happen. Okay, By the way, this line right here just relates to it was supposed to be where it started. Okay, so in this case, this was a negative value, So my spontaneity was negative, which means that this is gonna be X organic. All right, now, in terms of the rate, this one's kind of arbitrary, because I don't have I don't have actual units here or value assigned. What you can see is that I have a few different types of activation energies. I'm gonna have these that are about this big, and then I'm gonna have these down here. That about that big so we can kind of compare them to each other and say this one's gonna be somewhat fast, Okay, because I have a low activation energy. Okay, so it should be what a graph would look like. An A free energy diagram would look like if I had an extra chronic reaction that had a fast rate of reaction. Okay, so now what I wanna do is have you guys do the second one, so go for it.

Now that I've explained how to interpret these graphs thes next problems shouldn't be that bad. So this next one had a positive value of Delta G. So, since it was positive, that means this is an ender gone IQ reaction. I'm gonna have to put energy into the system to make it happen. The activation energy is about the same as before. Okay, So what that means is that this is also reaction That could happen quickly or fast. Okay, so I'm gonna have to put energy into the system, but once I do, it will happen relatively quickly. All right, so let's move on to the next one.

All right, So this one was a negative value of Delta G. So that means negative equals X organic again. And in this case, you see, the excavation energy got a lot bigger. It's about maybe three times bigger than I drew it before. So what that means is that this was gonna be take much, much longer toe happen, so this would be a slower rate. So it's to be a reaction that is favorable but doesn't actually happen at a very quick, quick pace. Okay, A type of reaction that might fall into this category might be like the burning of wood or whatever. Okay, So, like, wood is when it burns, it gives off carbon dioxide and it gives off, you know, heat and all of that is very, very favorable. That's a very favorable reaction, But does it happen just by itself? Does it just spontaneously burn? No. All right, so there's an example. It's because there's a very high activation energy required in order for combustion to take place. All right, so this would be an example of reaction that's very highly favored, but the activation energy is so high that it doesn't really happen unless we actually overcome the activation energy with heat. Okay. Like actually, like putting some lighter fluid and lighting it on fire. Whatever. All right, so let's go on to the last one.

all right, And finally, for this last one will take myself out of the picture so you can see better. But as you guys could see, my Delta G would be positive. So this would be an ender gone IQ reaction like before. But now this one's even gonna be less favored to happen or not less favored, but less likely to happen at an appreciable rate because my activation energy is so large, so it's gonna be difficult for destruction to take place. So this would be an example of a reaction that would not be very common in nature because it has not, only it's not very favored thermal dynamically, but then, on top of that, it just takes a really long time to happen. All right, so I hope that makes sense. So far, it's just a really quick intro to free energy diagrams. I hope that helped let's move onto the next topic