Gibbs Free Energy

by Jules Bruno
257 views
2
8
Was this helpful ?
2
Hey, guys, In this new video, we're gonna take a look at Gibbs Free Energy. Now, we've been talking about the system and the surroundings, and we've been talking about entropy and to a lesser extent, delta H Entropy. Now we're gonna take a look at the last major variable R Delta G value. We're going to say, we know that according to the second law of thermodynamics ah, spontaneous reaction will be when Delta as total or Delta s universe is greater than zero. But now we're gonna bring into the mix Delta G. Besides looking at Delta as total, it's also great to look at Delta G because knowing the sign for Delta G will be a great way to determine if your reaction is spontaneous or not. Overall, Now, to do this, we use two different equations here. We'll take a look at the one on the left side. It says Delta G zero equals Delta H zero minus T delta s zero. Remember these zero means that were under standard conditions and when it comes to thermal dynamics, standard conditions means one atmosphere and 25 degrees Celsius. And then on the other side we have Delta G equals Delta G zero plus r T l N Q. Here, this would be Delta G under nonstandard conditions. So we're not at one atmosphere or our temperature is not 25 degrees Celsius. Here it equals Delta G zero again, our here's our gas constant, which is 8.314 Jules over moles times K t is our temperature in Calvin que is known as our reaction quotient. Okay, we're gonna see our reaction quotient is just products overreact INTs, we're gonna say when it comes to queue, it ignores two states of matter. It ignores solids and liquids. So if it's a solid or liquid, it ignores it. If it's acquis or gashes or gas, it will look at them. Okay, so ignore solids and liquids. But look at a quiz and gasses. Now we're gonna say here if Delta G under nonstandard conditions is less than zero, then our reaction is spontaneous. If it's greater than zero than its non spontaneous and if it's equal to zero, then our reaction is at equilibrium. Now let's take a look at example one. And when it comes to this particular type of example, this is a standard type of question for any exams that you take that deal with Delta, G, Delta, H and Delta s. So remember our techniques that we use here in order to solve this particular type of question. Since we're gonna need room to see everything, I'm going to remove myself from the image guys. So we have more room to work with. Okay, The question says which of the following statements is true for the following reaction. So we have n 204 gas breaks down to give us to go to gas. We're going to stay here. The Delta H value is negative. The Delta s value is positive, and then we'll see that our options are the reaction could be spontaneous or non spontaneous, that petting on the types of temperatures we're talking about now in your book, there's gonna be a long large chart where you have to memorize different things. Now I say, Look, you can look at the chart, but there's a much easier way to handle the question like this That has to do with the little square thing that we have to the right side. So here, we're gonna use this image to help us figure out how to answer this question easily without having to learn a huge chart. So here we're gonna say we have our delta as values on top there positive and negative on the sides. We have our Delta H values positive and negative. Now, here's the thing we're gonna say when both Delta H and Delta s are positive, then our reaction is spontaneous at high temperatures at high temperatures. If Delta H is positive and Delta S is negative, then it's non spontaneous at all temperatures. So non at all temperatures. If Delta H is negative and Delta asked, is positive, then we're gonna say they're spontaneous at all temperatures. So spawn at all temperatures. Then finally, if Delta H and Delta s are both negative, then it's on Lee spontaneous at low temperatures. So it's gonna be high non spawn low, easy way to remember now if we go back to the question we have a Delta H, that's negative. A Delta s. That's positive. So when Delta H is negative and Delta s is positive, they said the reaction is spontaneous at all temperatures. Ah, question like this is very basic on your exam. So it's important you guys remember this quick, easy technique Instead of having toe sit down and memorize an entire graph an entire chart in your book. Just simply use this diagram. You can easily answer the question. The hard part really is just remembering who goes on the top who goes on the side. Just remember, Delta s values are on top. Delta H is are on the side. Then it's high, non spawn low and that's all. It iss an easy way to break down. Ah, very complicated issue. So just remember the steps. Remember how to draw this diagram and you'll be fine when it comes to a question like this.