00:00:08.300 --> 00:00:11.340 Hello there. This is Teacher Anderson, this is Chemistry Video 59. What we are going to learn today is how to use Gibbs Freedom 00:00:11.340 --> 00:00:15.620 Energy, which is the energy that can do work. I want to push now 00:00:15.620 --> 00:00:19.499 This sphere, it will move down, and then it will move back. This energy 00:00:19.499 --> 00:00:23.980 Where does it come from? This will be the transformation of gravity potential energy 00:00:23.980 --> 00:00:27.789 For kinetic energy. If we continue to make it move like this, it will eventually stay at the bottom. But if we treat this as 00:00:27.789 --> 00:00:31.949 A metaphor that illustrates what is happening in a chemical or physical change. 00:00:31.949 --> 00:00:37.190 What we have are reactants and products. These reactants are gradually becoming products, 00:00:37.190 --> 00:00:40.969 However, some products will spontaneously change back to reactants and eventually reach chemical equilibrium. our 00:00:40.969 --> 00:00:45.550 What about Gibbs Freedom? It became zero. So if we look at Gibbs free energy, it is 00:00:45.550 --> 00:00:51.859 Determine whether a response is a good indicator of spontaneous response. and so 00:00:51.859 --> 00:00:57.749 If Gibbs free energy is a negative number or less than 0, then we know that this is an autonomous 00:00:57.749 --> 00:01:01.820 reaction. We have such a scenario. Here we have some energy and this energy 00:01:01.820 --> 00:01:06.030 Can be released. If Delta G is greater than 0, then our scene will be 00:01:06.030 --> 00:01:10.330 Such. We had an uphill response, it was not spontaneous. 00:01:10.330 --> 00:01:13.580 In other words, we must give it a little energy for him to do work. then, 00:01:13.580 --> 00:01:17.850 We can reach equilibrium in the middle. In the previous video we learned that 00:01:17.850 --> 00:01:22.950 There are two things that can be used as Gibbs free energy, enthalpy and entropy. 00:01:22.950 --> 00:01:27.810 In other words, putting these two things together can help us determine whether it is a spontaneous reaction. 00:01:27.810 --> 00:01:32.300 However, this does not answer all questions. In this video, 00:01:32.300 --> 00:01:37.170 We will try to answer every question. What we are missing now is temperature. In other words, T 00:01:37.170 --> 00:01:40.700 Will be very important. So if we try to decide whether a response is spontaneous, 00:01:40.700 --> 00:01:46.100 One of the most important things is enthalpy or internal energy. 00:01:46.100 --> 00:01:49.950 So if our enthalpy changes, Delta H is negative, which can well indicate that our response is 00:01:49.950 --> 00:01:54.720 spontaneous. Therefore, in the aluminothermic reaction, the reactants have 00:01:54.720 --> 00:02:00.510 More energy. It was a downhill reaction. Therefore, we speculate that this response is spontaneous. 00:02:00.510 --> 00:02:04.880 Similarly, if we want to rust the iron, the same reason, we will react before the reaction than after the reaction. 00:02:04.880 --> 00:02:09.570 Have more energy. This energy will be released to 00:02:09.570 --> 00:02:13.880 Environment. But this rule does not always hold. Like this ice pack, if we think about it, 00:02:13.880 --> 00:02:19.450 Its melting is spontaneous, but at the same time it is consuming energy, and 00:02:19.450 --> 00:02:23.290 Our enthalpy change Delta H will be positive. Therefore, we cannot just consider 00:02:23.290 --> 00:02:27.670 Enthalpy change. We must also consider entropy changes. So if I have these two 00:02:27.670 --> 00:02:32.000 Ball, I charge some gas on the left side, if I open this valve, the gas on the left side 00:02:32.000 --> 00:02:37.150 Will move to the right. So we will have such an irreversible change. 00:02:37.150 --> 00:02:41.730 So what happened here? We cannot change any energy. What really changed was entropy. 00:02:41.730 --> 00:02:46.100 Putting two things together, enthalpy and entropy are helping us decide 00:02:46.100 --> 00:02:50.490 An important indicator of whether the response is spontaneous. So we can put it in such a 00:02:50.490 --> 00:02:54.210 Checkered. So if our enthalpy is decreasing, it will be an exotherm 00:02:54.210 --> 00:02:59.380 Reaction, if the entropy increases at the same time, we know immediately that it will be a spontaneous 00:02:59.380 --> 00:03:04.740 reaction. Similarly, if we have an opposite situation, our enthalpy is increasing, 00:03:04.740 --> 00:03:09.220 And the entropy is decreasing, and we know it will be an involuntary reaction. but 00:03:09.220 --> 00:03:13.950 Its reverse reaction is spontaneous. but 00:03:13.950 --> 00:03:17.470 But what will happen in the other two places? For example, we have 00:03:17.470 --> 00:03:22.930 Endothermic reaction, but our entropy is increasing. Or the other way around? A good example is 00:03:22.930 --> 00:03:27.730 Ice melts into water. If we pay attention to ice 00:03:27.730 --> 00:03:33.300 And water, the molecules of ice are very orderly. 00:03:33.300 --> 00:03:37.709 Many are due to these hydrogen bonds. If we look again at liquid water 00:03:37.709 --> 00:03:42.750 It can flow. So when we melt ice into water, what is it 00:03:42.750 --> 00:03:48.630 What kind of change? This is a simple melt and will be an enthalpy change. This represents 00:03:48.630 --> 00:03:53.420 what? This will be an endothermic process. It draws energy from its surroundings. 00:03:53.420 --> 00:03:58.160 So we will have a triangle ^ h which is positive. What happened to entropy? Our entropy 00:03:58.160 --> 00:04:02.569 Is increasing. In other words, our material is becoming increasingly chaotic. Well, in this picture, 00:04:02.569 --> 00:04:09.410 Where is this situation? Our enthalpy is increasing, and so is our entropy. 00:04:09.410 --> 00:04:12.520 Let's look at the reverse reaction. Let's say we want to freeze water into ice. 00:04:12.520 --> 00:04:17.620 What is going on here? This is an exothermic reaction. Therefore, the enthalpy is decreasing, 00:04:17.620 --> 00:04:21.870 Entropy is also decreasing. So in this picture, this represents this area. 00:04:21.870 --> 00:04:25.879 In other words, if we can understand this slide, we can understand that these two pieces are put together. 00:04:25.879 --> 00:04:30.949 What is going on. What do we know now? We know if we take a piece of ice 00:04:30.949 --> 00:04:35.930 Then put it in a place greater than 0 degrees Celsius, this will be 00:04:35.930 --> 00:04:40.520 A spontaneous reaction. In other words, as long as you put the ice on 00:04:40.520 --> 00:04:44.999 A place where the temperature exceeds 0 degrees Celsius, we know that ice will spontaneously 00:04:44.999 --> 00:04:49.490 melt. Similarly, if you take some water and place it at a temperature less than 0 degrees 00:04:49.490 --> 00:04:54.099 Somewhere, it will freeze. And we also know that if it happens to be at 0 degrees Celsius we 00:04:54.099 --> 00:04:58.039 No changes will be observed. This change will be involuntary in either direction. and so 00:04:58.039 --> 00:05:02.999 We have answered this question. So if we look at melting again, 00:05:02.999 --> 00:05:08.639 This is an enthalpy change, so this is an endothermic reaction, and at the same time 00:05:08.639 --> 00:05:13.779 Entropy changes, which will be spontaneous at high temperatures. same, 00:05:13.779 --> 00:05:20.479 If the enthalpy is decreasing, this is an exothermic reaction. If the entropy is decreasing, 00:05:20.479 --> 00:05:24.939 The reaction is spontaneous only at low temperatures. So now we can finally 00:05:24.939 --> 00:05:29.669 Consider Gibbs free energy. We should now understand this formula. 00:05:29.669 --> 00:05:33.620 So if we look at the formula of Josiah Willard Gibbs, Delta G 00:05:33.620 --> 00:05:39.770 Will be to the left of the equal sign. Remember that if this amount is less than 0, it will be a spontaneous reaction; 00:05:39.770 --> 00:05:44.669 If it is greater than 0, we know that this is a non-spontaneous reaction. This way, this equation 00:05:44.669 --> 00:05:49.110 It is clear. If you have this amount going down, it's a negative 00:05:49.110 --> 00:05:54.580 value. If the entropy is increasing, our delta S is positive, and when we subtract 00:05:54.580 --> 00:05:59.580 It we will get a negative value. Similarly, if we go to this non-spontaneous 00:05:59.580 --> 00:06:03.710 In response, our increment H will be a positive number. This will make Delta G 00:06:03.710 --> 00:06:08.319 rise. Then our increment S is negative when we subtract 00:06:08.319 --> 00:06:12.659 It is also a positive value. I hope you can understand both situations. but 00:06:12.659 --> 00:06:18.270 Now, let's take a look at these two cells again. What will happen if we increase the enthalpy? 00:06:18.270 --> 00:06:22.189 If we want to increase our enthalpy, this value 00:06:22.189 --> 00:06:27.749 Will increase our increment G. But if we have a high temperature environment, then our entropy 00:06:27.749 --> 00:06:34.169 Would be more important because we subtract this value. So even if we have a small enthalpy 00:06:34.169 --> 00:06:40.469 Or positive enthalpy, as long as we have a very high temperature and entropy increase, the reaction can proceed. same, 00:06:40.469 --> 00:06:45.619 In this case, if we can decrease the enthalpy, but 00:06:45.619 --> 00:06:51.699 Our entropy, even if it is falling, if we have a very low temperature, it 00:06:51.699 --> 00:06:55.669 There will be no major changes. Now we can explain that the ice pack is melting. How is this going 00:06:55.669 --> 00:07:01.199 How about it? Well we have an endothermic change, which is drawing energy from the surrounding environment. 00:07:01.199 --> 00:07:06.550 Our enthalpy increase is a positive value. Why do we have a spontaneous response? 00:07:06.550 --> 00:07:11.809 Ok we change ammonium nitrate to 00:07:11.809 --> 00:07:16.659 Ammonium and nitrate ions. As we go through this process, our entropy increases 00:07:16.659 --> 00:07:21.520 Even if our enthalpy increases so much, we still 00:07:21.520 --> 00:07:25.159 There is a spontaneous reaction. The Gibbs free energy variable will be negative. 00:07:25.159 --> 00:07:30.649 The Gibbs free energy formula is useful, 00:07:30.649 --> 00:07:34.819 Because it can tell us exactly what happens during a reaction. If it is less than 00:07:34.819 --> 00:07:39.529 0, the response is spontaneous. If it is greater than 0 this will not be spontaneous. in case 00:07:39.529 --> 00:07:46.529 It is equal to 0 and we are in equilibrium. I hope this video is helpful.
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