Química Inorgânica: o que o ENEM realmente cobra

追加: 2026-05-26

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[00:00:58][music] Listen. M.

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[00:02:48][music] Greetings, greetings, greetings, greetings.

[00:03:08]Welcome to another great review session for the ENEM exam. Today we're going to review inorganic chemistry, a topic that has been appearing fairly frequently on the ENEM exam. But today I'm going to bring a slightly different approach to inorganic chemistry, because there's a focus on what's covered in the ENEM exam and a focus on what's covered in university entrance exams. University entrance exams focus much more on terminology. The ENEM exam, on the other hand, focuses much more on context. You need to be able to interpret the question and identify which element will be used, especially in questions involving balance, pH, and soil correction. The 2025 ENEM exam, for example, included at least three questions on inorganic chemistry, and three or four questions relating to the regular ENEM exam, the ENEM Belém exam, and the ENEM PPL exam. In the regular ENEM exam, there was a question that involved much more analysis, and you had to assemble a molecule, right? An inorganic chemistry problem involves a bit of reactions. The Enem Belém and Enem BPL exams, however, included more specific questions addressing the concept of pH and correction. Well, the idea here is to do a review that is dynamic, quick, but very good. I've picked out three authorship issues for us to work on here today, okay? Three questions involving chemistry and inorganic mechanics to help you build this knowledge.

[00:04:39]Three key questions, three questions that will give you the foundation to answer any inorganic chemistry question on the ENEM exam. But to get started, we don't need to know your energy level. I'm actually quite hoarse because this afternoon I taught a 3- hour class at Memorize about the reproductive system. We're on an insane, absurd schedule of classes, okay?

[00:05:00]Well, here on YouTube we do more review classes, but for the people who are studying medicine at a higher level, for the people who really want to get a strong foundation to ace the exams at the end of the year, we have an intensive course, we have the more advanced students, we have the beginner group, and we're getting down to business this afternoon. Oh, this little lesson here, it was great, huh, guys? What did you think? There were a lot of people at the Memorize class this afternoon. Look at the level of our reproductive system class this afternoon on Memorize, working on the female hormonal system, and the original questions about the graph here. Well, that 's not the topic of today's biology class. Today's topic is chemistry, okay? I 'm here to teach you the basics of organic chemistry. I can get you everything you need for review in an hour, okay? For those who have already done it, there are only three questions today. Yes, because I'm going to try to do a review that's a bit more theoretical and active.

[00:05:53]So, in order for us to begin, I need the following. Have you already liked it, have you already sent your energy? I want this chat here, me vibrating. I want you all focused this afternoon here with me, okay?

[00:06:01]Listen up, I need you to grab a pen and paper, and some water to stay hydrated, so we can do a really good review of inorganic chemistry. Let me see how you guys are doing. How's it going? Let's go, then? I'm glad to see everyone so focused.

[00:06:16]Download the material to download transcripts, right? The link is pinned in the chat, it's memorizvestibular.com/lives.

[00:06:22]You can access the Memoris live streams, watch the replays, and also download the material, okay? Is the audio okay for you guys? Is the audio okay? Let me know if there's anything wrong here. If the audio is good, if I can play it, we 'll start our review of inorganic functions, okay? Let's go. Are you ready? Is everyone focused? I'm in the rhythm.

[00:06:48]He called already. Send a message to that friend and say something like: "Hey, Renato started the live stream, you're missing out." Or if you're watching this recorded live stream, the least you can do now is leave a comment right after saying: "I stopped by, Renato, I missed your live stream, but at least I saw the recording." Okay, let's go so we can get started.

[00:07:06]The audio is a bit strange. Let me check here. Wait a minute.

[00:07:17]Wait a minute, wait a minute, wait a minute.

[00:07:21]How is it now? Let's see. Is it better? Is it better? Is it better? It's better.

[00:07:29]I'm in the shower. Yeah. [laughs] I'm in the shower. How's the audio there? Is it better for you or not?

[00:07:35]Let me check here. Great. It's better. Awesome.

[00:07:38]So let's get to work.

[00:07:41]Awesome. Let's go then, huh? Let's get started. Grab some paper. Let's do a review. And if you have n't studied inorganic chemistry yet, I'm going to help you build that knowledge, build a very strong foundation here today, okay? We're in this together.

[00:07:54]Starting with the first little question, a cool question, one your grandma knows, huh? Your grandma will like it. An original question of mine here, okay? Has anyone here ever used Minâncora ointment?

[00:08:07]No stealing allowed.

[00:08:09]Look in the mirror, go to the bathroom, find the ointment, okay? Has anyone here ever seen Minâncora ointment, have you ever thought about it being on your ENEM exam? Well, right? This question is based on a question that already appeared on the ENEM, right? And it appeared on the 2025 ENEM, but it wasn't about Minâncora ointment. They don't mention Minâncora ointment, but it's the same content, okay?

[00:08:28]Okay? It got a little worse again. What's happening? Is it the internet?

[00:08:34]Let me check here, guys. Let me know if anything is glitching, okay? Or maybe it's just my voice, okay?

[00:08:44]Let me see here, man, what's going on?

[00:08:48]Wait a minute, let me see what's happening here. Is it better now? Okay, you guys or not?

[00:08:59]Let me see how I can change this audio to make it better.

[00:09:05]Ta-da-da-da-da. I think that's it, guys. I think that 's it.

[00:09:12]I think that's right. Okay, let's go.

[00:09:14]Let's play. Look, I'm going to read the question here and you're going to try to solve it with me, okay? Let's go, so we can start our first one, and then I'm going to review the content of inorganic functions.

[00:09:29]We're going to cover three topics today, okay? So let's go. Today we're going to work on the content of inorganic functions, mainly the inorganic chemistry part. I'm going to focus here on the functions, inorganic functions.

[00:09:42]Well, it's important that we follow a line of reasoning, first oxides, right? Then we'll move on to bases and acids, okay? And then we'll go to salts, okay?

[00:10:01]We're going to go through these three topics, these three parts, so we can delve deeper, okay? Okay?

[00:10:08]When you take The microphone sounds perfect, but then it goes away. Uh, I don't know what's going on here. I don't know what's happening, if it's something here. Let me see what's going on, what could be happening. Let me see if there's anything here.

[00:10:26]Hmm, I don't know, guys, what could be wrong here.

[00:10:31]When I lower my head, I'll have to change places here. I don't know where to change.

[00:10:44]Let's go. Okay. Better now. Can I play?

[00:10:47]Give me an oval if I can play so I'm okay. Everything alright? Tell me again.

[00:10:56]Can we start?

[00:10:58][laughs] Okay, okay. It got worse, [laughs] man. You're messing with me, messing with me. What am I going to do? Just keep playing like this.

[00:11:15]What am I going to do here, man?

[00:11:21]This is crazy.

[00:11:24]Better, better, better. Let's go, let 's go, let's go, let's go. Okay, [laughs] let's play like this. It's over. If it stays like this, it's over. Okay.

[00:11:32]Turn up the audio, turn up the sound, play the card, turn up the audio and we'll play the card. Let's start our review. Look. Let's go. Memorize 2026. It brings the following reasoning to us here. Look. Minâncora ointment is a demagogic product indicated, among other uses, for combating fungi on the skin. One of its active components is an oxide that can react with both acids and bases and it is classified as amphoteric, a property that makes it stable and suitable for use on the skin. The question is: among the following oxides, which ones exhibit amphoteric behavior would you mark? Which oxide is present in Minâncora ointment?

[00:12:20]Well, we have several types of oxides and it's important that you master their classification. I'm going to bring this review to you. Meanwhile, think about what these oxides would be and we'll bring the main reasoning, okay? So, which ones would they mark? In the 2nd, S3, ZNO, CO, F3O4.

[00:12:42]So, which one would you mark? I'll start our review and then I'll come back to this question. We're going to start by reviewing the content on oxides, okay? Initially, what is an oxide? Okay? To understand, oxides are nothing more than molecules, right?

[00:12:57]They form chemical bonds between a certain element and need to have oxygen, right? What is the characteristic for us to classify it as an oxide? Oxygen needs to be the most electronegative element. So, for us to have an oxide, oxygen needs to be the most electronegative element in the bond. The most electronegative. Okay?

[00:13:20]This is an important factor.

[00:13:22]Remembering that we have some coefficients, right? For example, I'll have here x O Y, that is, it's an element X with Y. And up here we have our charge, which is nothing more than C and the ion. That is, here always comes our C first and then comes our ion. So the value of Y here will be + Yx here, and here it will be -x. Let's take the example of a certain oxide. Here we have hydrogen, H2O.

[00:13:53]Why? Because oxygen has an oxidation number, if you remember correctly, of -2. And here hydrogen has an oxidation number of +1. So, when we move it here, we end up with two hydrogens. That's why it's H2O. This is an oxide, right? Water is a type of oxide. Be very careful, because, for example, OF here is not an oxide, okay?

[00:14:16]Why isn't OF2 here an oxide? Because fluorine is more electronegative than oxygen. And a rule for us to have an oxide is that oxygen must be the most electronegative element. So, what is an oxide? An oxide is a binary compound, right? So it has at least two elements, and it needs to have oxygen as the most electronegative element. Another example, look, CO2, right? What happens here? We have the oxidation numbers. So, if we put CO2 here, all Has anyone here ever studied oxidation numbers, or has anyone never even considered them? Tell me in the chat, does everyone know what oxidation number is? Oxidation number is simply the charge of an element, that is, how many electrons it needs to achieve the theoretical goal, right? To stabilize its electron shells. Have you studied oxidation numbers or not?

[00:14:58]Well, oxygen has a fixed oxidation number, right? An oxidation number of -2, right? And then carbon, well, its oxidation number will vary, right? In this case, the number here will increase to +2, right? Okay? And then we'll make simplifications, balancing our elements correctly, right? In the case of carbon here, right? CO2 will have an oxidation number of +4, actually, right? To balance it.

[00:15:21]But then we make the cuts and arrive at the molecules, okay?

[00:15:24]This is also a type of oxide that we'll have, okay? So we have CO2 going up there, Right? There's only one oxygen atom, and we can balance it. Okay?

[00:15:33]Well, guys, what's most important for the ENEM exam regarding oxides? When we talk about oxides, we also talk about bases and acids.

[00:15:41]Usually, the entrance exam will test the concept of nomenclature, which is what students fear most. Oh my God, Renato, I'm so afraid I won't remember the name, how am I going to name the variable oxide, how do I do this, etc. But the ENEM exam doesn't test the nomenclature of oxides, it tests bases, acids, salts, it tests classification. So what you need to know most here is the classification of oxides. That's all that matters for the ENEM exam. And when we classify an oxide, we can start by classifying our basic oxides first, okay? What are basic oxides? Basic oxides are acids that, when placed in water, produce a base. So, a basic oxide is nothing more than... That's more than a certain oxide. When I put that oxide in water, that is, H2O, it will produce a base, okay? Or if I put it in an acid, it will produce a salt.

[00:16:39]So, it leads to a neutralization process, okay? If we bring in the idea of ​​classification, what are oxides? It's not a nonmetal, right? It's a metal, right?

[00:16:51]It's a metal plus oxygen.

[00:16:55]Why isn't it a nonmetal? Because, look, one of the characteristics of oxides is that they bond with a metal. Think about the periodic table, tell me which elements have basic characteristics.

[00:17:06]Clearly, it will be those that are part of the alkali group, like alkaline metals.

[00:17:12]So it's groups one and two of the periodic table, because they have oxidation states of +1 and +2. The periodic table lesson is one of the most important lessons, and if you don't know the periodic table, you'll have to take 300 steps back to start giving you the real content, because the periodic table is the beginning of a project. If you don't have the periodic table... By simply reading the periodic table in your head, you won't learn anything about chemistry. The periodic table organizes the elements and gives you a great shortcut.

[00:17:36]When you look at it, you have group one and group two of the periodic table.

[00:17:39]Group one and group two are metals.

[00:17:42]These initial metals form oxides, they bond with oxygen. So, in this case, I 'll have a metal. Oxygen has an oxidation number of -2. And I need this metal to have an oxidation number that can be +1 or +2, right? It can't be more than three, okay? The oxidation number can only be +1 or +2. Therefore, if you look at the periodic table, when you look at the drawing of the periodic table, what elements appear there? Of course, you'll remember sodium, of course you'll remember potassium, of course you'll remember magnesium, and of course you'll remember calcium. All of these are oxides that we call basic oxides. Of course, the elements in group one are the most basic oxides, they are the... more soluble in water.

[00:18:26]So, if you take, for example, potassium oxide, sodium oxide, if you take, for example, magnesium oxide, all of these will form basic oxides, right? Because the oxidation number cannot be three, because if it is three it is no longer a basic metal, that 's a rule. Oh, and in that case it no longer has basic characteristics. When the oxide bonds with an element that has an oxidation number of +3, that element already has another property, it is no longer a basic oxide. Then it receives another characteristic, it would already be an amphoteric oxide. The property of the oxides, the properties of the oxidation number are fundamental. Here we already have a classification. What you do is memorize: basic oxides are metals with an oxidation number of +1 or more of the simple one. That's it, right? And then we're done, okay? No, no, live, it wasn't 7 pm. But what time is it now? [laughs] What time is it now? Hey you guys? For me, it's only 7 o'clock now. Let's go. Look.

[00:19:26]Basic. Put it in water and it forms a basic compound. Let's give some classic examples, right? When we put Na and O here, what do we put here? Oxygen has an oxidation number of -2, so it means I'll need two oxygens. So, my molecule is N2, see? Okay? This is an example of a basic oxide, okay? This is an example of a basic oxide. How do I name it? It's very simple.

[00:19:52]The name will simply be sodium oxide, okay? And this is an oxide with basic characteristics. We have another very famous one, right? What is another very famous oxide? This one. We take calcium and we take oxygen. What is the oxidation number of oxygen? -2. What is the oxidation number of calcium? Since it's in group two of the periodic table, plus two. If we cross the charges, I'll have two plus two here. Ca2, Okay, I can shorten it, shorten it to simplify. This is the same thing as CaO. What is this? Calcium oxide.

[00:20:29]Do you know it? Very important for a soil correction process, like liming, calcium oxide, the famous lime, okay? These are some of the famous oxides we have. What other famous oxides do I have here? I can have this one, Fe. And what is this one? Well, this one, look, it 's Fe. If I take the oxide here, this one has -2. So, in this case, I have an iron plus 2. But iron doesn't have a fixed oxidation number. There are elements that have fixed oxidation numbers and others that don't.

[00:21:00]Iron doesn't. And when it doesn't have one, I have to put its oxidation number.

[00:21:03]In this case, this is iron oxide two.

[00:21:09]Can I have iron oxide three? Yes, but then it would be FeO. And in that case, if it's plus 3, I'll cross the... So it becomes Fe₂O₃. So I can have, for example, here iron oxide. Why, Renato? Because then the oxidation number is iron 3 and the oxygen is +2.

[00:21:27]Mastering oxidation numbers is fundamental for you to start understanding the part about oxides, right? So here, all of these, folks, start to be basic oxides.

[00:21:36]So, pay attention. Look, Fe here with an oxidation number of +2, it's classified as a basic oxide. We have some other types of oxides, for example, that may appear on this exam.

[00:21:46]Look, Mg₂O, right? Look, this is another one that sometimes appears a lot on your exam, Mg₂O, right? It also appears as a type of basic oxide, right?

[00:21:57]Okay, cool. What are basic oxides for you? Okay, right? How do I name them? It's simply oxide of and the name of the element, sodium oxide, potassium oxide, Calcium oxide, when the nox is fixed, when it's not, you put the Roman numeral nox, for example, iron oxide two, copper oxide one, okay?

[00:22:17]Silver oxide. Okay? It's very simple. These are classified as basic oxides.

[00:22:23]Renato, there isn't only this type of basic oxide, right? We have other types of oxides as well. Take a screenshot because I'm not going to save everything. I'll draw it and then you can come back to the live stream and watch it again, okay? I'll erase here, we'll build it up. Okay, Renato? I already know I have the basic oxides. What other types of oxides do I have here?

[00:22:43]Well, we can have oxides, folks, that are called amphoteric oxides, okay? So, write this down: amphoteric oxides.

[00:22:52]What are amphoteric oxides? That's what the question asked you.

[00:22:56]Amphoteric oxides are Oxides, while this one here is Mo, and this metal needs to have an oxidation number of +1 or more. Here I'll have the option of photon, where I have an oxygen metal, and this metal has an oxidation number of +3 or +4. Look, the oxidation number increases over time. An oxide foo, this prefix here amphi, comes, for example, from amphibiotic, amphipathic molecule. Amphoteric means that here I have an oxide that behaves as a base and behaves as an acid at the same time. So, when I have an oxide foo, it means that it can be basic or acidic, depending on the medium. If I put it in an acid, it behaves as a base. If I put it in a base, it behaves as an acid. And if I put it in a neutral environment, it remains neutral. So, the idea of ​​the oxide foo is that it can behave in both ways, as a base and as an acid, okay? Depending on the medium. If I put it in an acid, it will neutralize the acid. If I put it in a base, it will neutralize the base. And if I put it in a neutral medium, it will maintain and leave the medium neutral. This is an amphoteric oxide. We have some classic examples that come up on tests for you, such as aluminum oxide, aluminum, and oxygen. The oxidation number of oxygen is -2. The oxidation number of aluminum is fixed at +3. In this case, if I cross the charges, I have 3 and 2 here. L2O3 is an amphoteric oxide, okay? Aluminum oxide.

[00:24:26]Now here, Pb, look, I have lead oxide. In this case, I have Pb, and I have oxygen here. Well, look, oxygen has an oxidation number of -2. And here, lead, to equalize, if I have an oxidation number of -2 here, it will be, look, 2 x -2. Here I will have an oxidation number of -4, and here it needs to be +4, and the result is zero. So here I have +4 oxidation number, okay? This is the PBO2 is lead oxide 4.

[00:24:54]Lead oxide 4.

[00:24:57]Why is it an amphoteric oxide?

[00:24:59]Because it has an oxidation number of +4. Because it has an oxidation number of +3. So, through the oxidation number, that's how you define if it's an amphoteric oxide, okay? So, just by the oxidation number I can distinguish it. If the oxidation number is greater than oxygen, I call it amphoteric; it 's not greater than oxygen. You analyze it by the oxidation number of the element; oxygen is fixed, minus 2. So you analyze, for example, +1, +2, +3, or +4. In fact, that's the only way to analyze an element, right? It's not just by the oxidation number, it's through the oxidation number. There wouldn't be another initial way without using the oxidation number, but be careful, okay? Because there are exceptions here. The main characteristic isn't just the oxidation number, it's two combinations. What is a basic oxide? It's an oxide that has a metal, that has an oxidation number of +1 or +2, and when I put it in Water, H2O, forms a base. That is, look at that word.

[00:25:51]When I put it in water, it forms a base.

[00:25:54]Now, an amphoteric oxide, how do I classify it? First, I have a metal bonded to oxygen, and this metal has an oxidation number of +3 or +4. And when I put it in an acid, it forms, that is, it neutralizes in an acid. It reacts as a base, and when I put it with a basic compound, it reacts as an acid. That's an amphoteric oxide, meaning it has a dual behavior. But then exceptions arise from this. What are the exceptions? There are elements that can act according to exceptions, right?

[00:26:27]We'll talk a little bit about these exceptions here for you. Well, I have three here, an oxide that is what?

[00:26:33]An acidic oxide. And what are acidic oxides? Guess what? It follows the sequence of oxidation numbers. Acidic oxides are oxides where I have a metal and I have oxygen. And this metal has oxidation numbers of +5, +6. Or more than 7. And that's the maximum, right? There's no oxidation number higher than seven. Seven is the maximum in terms of oxidation numbers, right?

[00:26:57]Because then we're closing the last ones there, right? Plus 1, +2, +3, +4, +5, +6 or +7 or any metal. So here it's a metal that has an oxidation number of +5, +6 or +7 or any nonmetal.

[00:27:14]We have here any nonmetallic oxide.

[00:27:18]Let's look at some examples of acidic oxides we can have. Well, to work with acidic oxides here, we're already working with the idea of ​​a metal, right? You see here we're already working with the idea of ​​an element, we could put it here, right? So it's an element, right? Bonded to an oxygen. This element can be a metal with an oxidation number of +5, +6 or +7 or any nonmetal. And from here I already have an oxide of the acidic type, right? So let's take some examples of oxides here. I can take Here for you, right? Uh, within the idea, uh, let's think about a type of oxide-acid.

[00:27:50]Well, the most classic ones we'll have, we can take sulfur, right?

[00:27:55]Sulfur is a classic oxide, you must have seen it, for example, SO2, this one here, SO2, what is the oxidation number we'll have for sulfur when we calculate it? Well, SO2, when we analyze it, has an oxidation number of +4. Renato, shouldn't it be more C when it's a metal?

[00:28:13]When it's a metal, the n The oxidation number has to be +5, +6, +7. Sulfur is a nonmetal.

[00:28:19]So, since sulfur is a nonmetal, any nonmetal with oxygen is an oxide.

[00:28:23]If I take CO2, for example, CO2 is also an oxide, okay? If I take iodine here, iodine is also an oxide; any nonmetallic element, of course, that is less electronegative than oxygen, will form an oxide for us, okay?

[00:28:39]Or you can take any metal that has an oxidation number of +5, +6, or +7, okay? We've got three classifications: basic oxides, amphoteric oxides, and acidic oxides. So, going back to our question, the question is: which of these is an amphoteric oxide? Have you guessed it yet? Nobody in the chat managed to answer this question without having to search on Google. Wouldn't you be able to answer it either? Your passing grade on the ENEM exam is worth it. You don't know how to answer this question correctly?

[00:29:08]Otherwise, things are getting complicated for you, huh?

[00:29:13]Business got tight. Which of these is an amphoteric oxide?

[00:29:18]Let's go. Look, the first one here, you should clearly know, is a basic oxide. Why is it a basic oxide? Because I just explained to you that basic oxides are elements that have one or more oxides. In this case, sodium is in group one of the periodic table. So he has an x plus one. This is a basic oxide. If I take SO3, SO3 is a nonmetal with oxygen. So this is an acidic oxide, right? So SO3, which has an oxide here plus 6, right? It is an acidic oxide. And what about ZNO? So, does zinc have stainless steel fixed in it or not, guys? Zinc, zinc has it.

[00:30:06]Zinc has a fixed oxidation number.

[00:30:10]ZNO. Oxygen has an oxidation number of -2 and zinc has an oxidation number of +2. So, guys, what would be the most basic oxide? So it is. But zinc is one of the exceptions. Zinc is an amphoteric oxide. And yes, you have an obligation to know it by heart, okay? Unlike some chat rooms that rely on memory, where people know things by heart, Zinc is an exception. When we talk about amphoteric oxides here, which we were working on, there are the famous exceptions.

[00:30:42]Why an exception? Because they are oxides that have more stainless steel content than, for example, and react with both acid and base. It exhibits anoteric behavior. What are the exceptions you need to keep in mind? Okay, we have ZnO, we have, oops, let's put ZnO here, SnO, which is strange. We have PBO, which is lead oxide, okay? These are oxides that have an oxidation number greater than 2. All of these here have an oxidation number of +2, +2, or +2. And they are considered amphoteric, okay?

[00:31:21]These are oxides that you need to memorize.

[00:31:23]When you take this Minâncorra ointment, if you open it and take a look, you'll see that it contains zinc oxide, okay? Zinc oxide, which is the phosphoric oxide that can neutralize and kill those fungi, right? So here we would arrive at the answer that zinc oxide is a phosphoric oxide. And CO, Renato, CO is a neutral oxide, which is a fourth classification that we hadn't discussed yet.

[00:31:53]Neutral oxides are those oxides that do not react with either acids or bases; they do not react with water. What are the neutral oxides? You can write down the tip: water on the invitation.

[00:32:09]What are the neutral oxide types? Well, you might remember water, H2O, NO, which is why it's not an invitation, CO which is carbon monoxide, and this 20 here, right?

[00:32:23]Remember 20? With 20, remember with 20 here. This would be N2O, right? Remember this, look, the N20.

[00:32:32]N20, okay? It would be N2O. These would be the oxides classified as neutral, right?

[00:32:39]Here we have dinitrogen monoxide, which is nothing more than water, H2O, oxygen monoxide, nitric oxide already working here, carbon monoxide, and nitrogen monoxide, okay? It's N2O. These are the neutral oxides that we have here. So CO is a neutral oxide. One important application is that CO₂ is toxic, right?

[00:33:05]That's another application that could come up on your test, right? You know that we can have CO2 from combustion and you can have carbon monoxide. CO2 is a greenhouse gas, right?

[00:33:16]And CO, which is carbon monoxide, has an affinity for hemoglobin; it can bind to the M group, right? And then it takes the place of oxygen, so it forms carboxyhemoglobin and can lead to asphyxiation, okay? So CO is dangerous because of that.

[00:33:34]Nitrogen monoxide is also kind of dangerous there, right? N2O is less so, but nitrogen monoxide is also dangerous. They are all worked on here as well. They come from the incomplete combustion of car exhaust fumes, for example. So when you get a car and you get the automotive catalytic converter, right? Remember, for example, the automotive catalytic converter, right? Imagine this: you have a car here, and then you have a catalytic converter over there. When you have incomplete combustion of these elements, what will you get? The formation of oxides, such as CO, for example, and NO. This is formed during the incomplete combustion of fuel in a car. But you don't want to release these components here because they're dangerous, right? So here you have an automotive filter, you have the catalytic converter, and then you release the CO2 from the exhaust, okay? You release NO2 there, for example, right? You release other molecules that are less dangerous to respiration, to humans. Well, sure they're pollutants, they contribute to the greenhouse effect, but they wouldn't lead to death, right? You don't die from breathing CO2. Even I'm releasing CO2 right now, I'm producing CO2 all the time, right? In the cycle of cerebrums, I'm releasing CO2 all the time. The problem then is breathing with monoxomic symptoms. Monoxus is very dangerous, okay? Was the metal with oxygen not acidic? Metal with oxygen was acidic. Yes, the metal with oxygen. But here we have the exceptions. In this case, we have neutral oxides, okay? Look, the characteristic of an acid is a metal element with an oxidation number of +5, +6, or +7, or any nonmetal that, when in contact with water, forms an acid, right? So it's not just about looking at the element, it's about thinking about the element that I put in water, does it form an acid? Or if I mix it with a base, it neutralizes and forms a salt.

[00:35:28]So, I don't classify acids by oxidation number, I don't classify acids by metal or nonmetal, so it's always a combination. You have to be careful with this idea of ​​a prank, right? So it's always a combination, they are elements that have a certain oxidation number and their behavior.

[00:35:46]That's why exceptions arise, because these ones, for example, have oxidation states of +2, +2, and +2. But when I put them in water, or in a steel base, they behave like amphoteric surfactants. If it were based on the oxidation number, I would classify it as basic, but because they behave this way, I classify it as a photon. Like CO, since it's a metal, I would classify it as an acid. But when I put it in water or mix it with the base, it's neutral; it doesn't react.

[00:36:15]Carbon monoxide does not react with water. That's why he's neutral, right?

[00:36:19]So we classify it as neutral because it doesn't react with water. And this Fe3 and O4 here, well, these are called double, mixed, or saline oxides, right? It's a more specific classification. Whenever this F2, E3 appears, it is classified as a mixed or saline double ovule. These are the main classifications we have here in relation to Fe3O4 and the other bones from here. Do you have any other examples? Yes, okay? The last classifications we could have would be, for example, H2O2. These are the famous peroxides, okay? Peroxides are oxides in which oxygen has an oxidation number of -1, okay? So the traditional oxidation number of oxygen would be -2, but oxygen can have an oxidation number of -1, and then it's classified as a peroxide, okay? There's another classification here, for example, we can take a molecule that is N2O4 or here, look, it could be this one right here, N2O4. In this case, I have a specific fixed oxidation number for this element, right? In this case, ã, it's na, right?

[00:37:31]Here, in number 2, right? I have a fixed oxidation number of one here, so the oxygen oxidation number here also becomes -1, okay? These are called superoxides, okay? Superoxides. In the case of molecules, this one, for example, is hydrogen peroxide. He's very dangerous, isn't he? It forms free radicals there, right? So we combat the hydrogen peroxides formed in the body. So there are yet another classifications. These are the most important oxide classifications that you need to have memorized.

[00:38:06]Oxides can be classified into basic, acidic, amphoteric, neutron, double mysine, peroxide, or superoxide oxides. The ENEM exam doesn't test nomenclature; the ENEM exam tests classification.

[00:38:22]And what is the importance, the applicability of these oxides? Does this make sense to you? They are also able to capture the carbon atoms, which also compete for the active site in cellular respiration, right? So we have cytochrome oxidase, which is a protein, and carbon monoxide also causes asphyxiation in that process, right?

[00:38:43]Interrupting the chain of electrons there, right? The site is active. Well, always remember, this classification of oxides is a fundamental basis. Remember the exceptions, okay? The ENEM exam already covered the exception in the last ENEM 2025 exam; it covered some of the exceptions. So, if I'm bringing this up for you, it's because the ENEM exam has been asking about these exceptions, like ZNO, like oxon fóter, trying to get away from the basics, okay? So you also need to pay closer attention to the more specific details. Let's move on to question two here so we can continue our in-depth analysis. Look, this one's a classic, right? Here the oxidation number is -1/2. The oxidation number here is -1/2, right? - 1/2 here, just to remind you, exactly, about hydrogen peroxides. So here it 's -1 and here it's -1/2, okay? Fe3O4 would be the combination of two oxo compounds. Exactly.

[00:39:34]That's why they're called double oxides, mixed oxides, or saline oxides, right? That's because where does it come from to form, for example, Fe3O4, right? The guys are really out of it, they're crazy. F3O4 here, look.

[00:39:46]F3O4, right? To form it, I need the FO, and I need one more here, right? I need FE2 here, the one from here, right? Three, right? Beauty? So I need one more Nóx here, plus two more, right?

[00:40:02]Iron two and one knot here, iron three, right? So the combination of iron oxide three and the combination of iron oxide four form the mixed double oxide, right?

[00:40:10]So it is mixed, double, because it is a combination of two oxides. Beauty? This fits into the idea of ​​synthesis, the idea of construction, okay? They're flying high.

[00:40:22]Huh? Well, that's easy, right? Easy peasy.

[00:40:25]Let's continue our review there. Let's go read the next question to me here.

[00:40:28]Look, she tells us the following: "In a vegetable plantation, soil analysis revealed that it is excessively acidic. Okay? A condition that impairs nutrient absorption by the roots. To correct this problem, without resorting to strong bases that could cause abrupt and damaging changes, the agronomist decided to use a salt that, upon undergoing hydrolysis in an aqueous medium, gradually raises the soil pH, making the medium less acidic.

[00:40:57]Five salts are available in stock, all soluble in water. Considering the behavior of these salts in aqueous solution, the appropriate salt to correct the soil acidity is... and now? Well, classically, the ENEM exam doesn't specifically cover bases and acids, right? If I were to tell you within the classifications, when we talk about bases and acids, right? Uh, it's very straightforward. If we think about the following idea, what is a base? A base is a basic compound. Oh, of course, right, Renato? A base is a basic compound. A basic compound is one that has a pH above seven. On the pH scale, imagine that seven would be a neutral pH, right? So, the closer to zero, or here 14, the more acidic, the more basic, right? The lower than seven, the more acidic on the pH scale. When I talk about a base, a base is a compound that undergoes ionic dissociation in water, that is, separation.

[00:42:01]So, a base is a compound that, when placed in water, releases hydroxide ions (OH-). This OH here is called hydroxide (OH-). This is what we call ionic dissociation. Some people don't know the difference between ionic dissociation and ionization. So, guys, are you all good with this? What is ionic dissociation? And especially, what is the difference between ionic dissociation and ionization?

[00:42:27]Well, the difference between ionic dissociation and ionization is that ionic dissociation presupposes that you already had ions before.

[00:42:35]Imagine the following, the dissociation Ionic bonding, we have an ionic bond, and an ionic bond is a bond between a metal and a nonmetal. For example, if I have Na here, and OH here, in the idea of ​​ionic dissociation, when I put it in water, I separate N+ + OH-. But you notice that there was already a positive charge and a negative charge here. That's ionic dissociation. If I take COH2, for example, here I also have ionic dissociation, I form C2+ + 2OH-, that is, here I am dissociating the ions, the canions, right? Now, ionization comes from a covalent bond. A covalent bond. A covalent bond is a bond where I did n't have these ions when I break that bond.

[00:43:36]So, when I break that bond, I have an ionization process, that is, I form ions. An example here that we can have is HCl, hydrochloric acid. Look So, HCl forms H+ and Cl- for us, right? H+ doesn't exist alone, C- doesn't exist alone.

[00:43:57]H+ can only appear when a bond is broken. When we look at molecules, what exists is H2. There's hydrogen gas, there's chlorine gas, but there's no Cl. H- doesn't exist alone. This only exists when I break a bond. That is, the cleavage of the bond between H+ here, hydrogen, is what forms H+. The cleavage of the bond between C and Cl. They only arise here through a cleavage process. I have to break a bond to create an ionic species here, right? Otherwise, they will always be in nature in the form of C2 or H2. That's how I find the element in nature, okay? It's always joined together, for example, F2 or Br2, right? These elements are always paired here, always together. That's ionization, forming ions. And ionic dissociation is what creates N+ or C2+ here. This does exist. I can release it in water. I'll find the presence of C2+ there. Okay?

[00:45:05]That's the difference between ionic dissociation and base ionization. So what will we have? It will be that compound that, when I put it in water, releases OH-.

[00:45:12]So the general idea of ​​bases, we can arrive at the following molecular formula : a base always has a ion, so I identify a base when it has an OH-, this base will have to be a metal, and this metal has to be the metal or NH4, right? So to be a base here, I will have a certain element that can be a metal, okay? Or it can be NH4, which is the ammonium ion, right? So ammonium or metal can form bases. That's where some theories arise, right? The theory there said the following: a base is that compound that, when I put it in water, releases OH-, and with that we put the metals. And then I had the famous bases like NaOH, sodium hydroxide, right? Or COOH, calcium hydroxide dissolved in water, which releases OH-.

[00:45:59]Hydroxyl group. Until the moment when other theories emerged, right? The acid-base theories of rhenium, of lusitania. And then other theories emerged that also presented the base to us, like that compound that has NH4+, that is, the base can have this compound here, right? The NH4+ there, OH can be a compound that comes from the base, comes from ammonia, okay? That's another example we'll have. Well, this is the classification of bases that we'll have. It's important that you know some things that may be on the test about what a strong base is and what a weak base is. Strong bases are bases from groups one and two of the periodic table, but that's a fact, it's obvious to you. Because remember that the periodic table has the alkali metals and alkaline earth metals? So it's a fact that when I have a hydroxyl group bonded to an alkali metal, I will have a very strong base. When I have a base there, a hydroxyl group bonded to an alkaline earth metal, I will have a base.

[00:46:49]Very strong.

[00:46:50]The weakest bases are those bases bonded to any metal other than those in the alkali metal family.

[00:46:57]So, for example, we have aluminum hydroxide, iron hydroxide. These elements are weaker bases, okay? They are weaker bases, okay? It's not NH3 that's basic. You're confusing the difference between a basic compound and a base. Look, NH3 is a basic compound, okay? But here we're talking about the element bonded to the hydroxyl group. To be classified as a base, it has to be a metal, okay? Or NH4, okay? Or NH4.

[00:47:34]And why can NH3 be classified as a base? Because NH4OH, when placed in water, produces a base, you understand? And this is already a theory of organic chemistry, right? So, when we look at the formation of ammonia, which is a basic compound, we have it starting from NH4, right? So, the formation here, the formation of... The basic compound comes precisely from that. Ah, why is ammonia considered a basic organic compound, right, NH3? That's where the theory comes in, right? What was their theory? Their theory was that a base is a compound that, when I put it in water, that hydroxyl group undergoes dissociation, right, the OH, and then it forms a base. But then they went and saw that, hey, but what about NH4? When I put it in water, it also forms a base, there's no hydroxyl group here, you understand? I'm putting it in water, it's forming a base, and there's no hydroxyl group. And then? And that's when they arrived at the compound NH4 and ammonium, which is also classified as a basic compound here, right? Of course, NH4 here with the idea of ​​OH, right, along with the idea of ​​water, okay? Alright? And it's ammonia, in this case, NH3. Ammonia itself is basic, no, NH4 is not basic. NH4 is in the place of the metal, when I I put it here, NH4 + OH, this compound here is a basic compound, okay? Great? Awesome.

[00:49:10]Let's go, huh? Following our reasoning a little further. If a base is this, what is an acid, right? If a base is this, what is an acid? So, well, an acid, in this case, is a compound that when I put it in water, releases a proton or a hydronium ion, also called a hydroxonium ion. Renato, I've never heard of that, have I? Definition of argens. Well, it's that compound that when I put it in water, it releases an H+. This is a proton, which is the same thing as an H3O+, right? This here is called a proton, right? Or here it's called a hydronium ion, right? So when I put it in water, this is released, this compound is basic. The more H+ I release, the lower the pH will be, right?

[00:49:55]The more H+ is released, the more acidic the place is. The more acidic the place becomes. To classify as Acids: We can have two types of acids, called hydracids or oxyacids. What are hydracids? Hydracids are compounds that contain hydrogen and some other element, right? So here I have a hydrate, which is one without oxygen. Let's take an example. HCl, hydrochloric acid, is a hydracid. H2S, hydrogen sulfide, is a hydracid without oxygen, okay? Or I can have oxyacids. In this case, I will have hydrogen, some other element, and the presence of oxygen, okay?

[00:50:37]So here's an example of an oxyacid: H2SO4, this is an oxyacid. What other example can we have here? I don't know, HNO3 is another example of an oxyacid.

[00:50:48]Okay? So here I have the presence of oxygen. Great. These are hydracids, okay? You have to know the idea of ​​differentiation, right? To name them, it's good to know the oxidation number or memorize the maximum oxidation number of the molecule, and -ous for the weakest. It's important, not for the ENEM exam, okay? So, that nomenclature -io, -oso, -ato, whatever, is very important, but it's not ENEM content.

[00:51:14]We cover that content in detail, the nomenclature, knowing the nodes and everything else, but the ENEM doesn't care about that. It never tests nomenclature. The ENEM doesn't test the nomenclature of oxides, bases, or acids. The ENEM tests everyday application. The ENEM tests utility. That is, which acid would you use, for example, to neutralize soil? Which acid is in a soft drink? Or what does neutralization generate? Or what acid is rain made of? The ENEM tests context, because the ENEM tests skills and competence. It's different from the vestibular exam, which tests content. The vestibular exam will test inorganic chemistry, the ENEM will test skills related to nature, right?

[00:51:57]Relating the acidic compound to the environment and environmental impacts.

[00:52:02]Relating the agricultural project to the neutralization of organic compounds. Very much so. That's crazy, right? So the ENEM exam is very different. That's the basis you need to understand about the difference in the test. If you're taking the vestibular exam, you'll have to know the specific nomenclature of each type of acid. If you're taking the ENEM, you have to know the classification of acids. So, differentiate between what is a base and what is an acid, okay? Okay? Well, if I already know what an acid is and what a base is, I know what a neutralization reaction is. A neutralization reaction is taking an acidic compound plus a base, and every neutralization reaction produces a salt.

[00:52:44]The most classic neutralization reaction is taking an acid like hydrochloric acid plus a base like sodium hydroxide.

[00:52:54]And in this neutralization reaction, I combine a cation with an anion, I combine H with OH, forming water. So here I form a salt: sodium chloride (NaCl) plus water ( H2O). That's the most classic neutralization reaction we have.

[00:53:13]Okay?

[00:53:15]From this, we can classify acids and bases according to their strength.

[00:53:21]Well, you know that a strong base is one from groups one and two of the periodic table, with group one being the strongest bases. And acids, what are the acids? Well, hydrohalic acids tend to be stronger acids; that is, if you take hydrochloric acid, hydrogen sulfide, they tend to be somewhat stronger acids. The strength of an acid has to do with the number of hydrogens it can release, in this case protons, right?

[00:53:47]Ionizable hydrogens. So, when we take an acid, when I say that this acid here is a mono-acid, it only has one hydrogen to be released, only one H+. In the case of sulfur H2SO4, it is a protic acid or diacid because it has 2 H+ to be released, okay? Okay? Now, regarding the strengths of acids, what is important for you to know is which are the strongest acids? HCl, HBr, and HI. That is, the strongest acids... If we were to classify them, they would be the following: HCl, HBr, okay? HBr and HI are the strongest acids we have, the strongest inorganic acids. HF is a moderate acid. We have a moderate acid, produced in the halogen family. HF is a moderate acid. And the weakest acids here, that is, weak acids, we can mention H2S, which is sulfuric acid, the one from rotten eggs, and HCN, which is hydrocyanic acid, which has cyanide, okay? When we talk about hydracids and when I talk about oxyacids, then we have to calculate the strength of this acid. So you can calculate the strength of this acid, which is to take the number of oxygens minus the number of hydrogens. You can memorize it like this: a strong acid is based on the idea of ​​ionization, that is, subtracting the oxygens from the hydrogens. When it is greater than one, the result is a strong acid. Moderate is equal to Okay? That is, it equals one. And weak, we have that acid where the result is less than one, okay? Or equal to zero. So, if I take sulfuric acid here, I'll have four oxygens and two hydrogens. So, 4 - 2, the result here is 2. That is, this one is classified as a strong oxide.

[00:55:43]If I take HNO3 here, HNO3 is three oxygens for one hydrogen. So, the result here will be two. So it's classified as a strong oxide.

[00:55:53]Okay? The classification is straightforward.

[00:55:56]Now if I take HNO2 here, okay? HNO2 is two oxygens for one hydrogen. So 2 - 1 result equals 1. This one is classified as a moderate acid.

[00:56:09]The strength of this acid is classified as a moderate acid. Now be careful because there will always be the famous exceptions. When you take, for example, H2CO3, right? H2CO3, if you took it, would be three oxygens for two hydrogens. 3 - 2 result Equal to 1 moderate. No, it's not moderate. H2SO3 is classified as a weak type.

[00:56:36]Why is it classified as weak? Because it separates. When I put it in water, it breaks down quickly, it ionizes very easily into CO2 and water.

[00:56:47]This one here, which is carbonic acid, when we have it here, will also be the acid in soda. It's considered weak, it's used in soda precisely because of its separation into CO2 and water, right? It's even related to the process of ocean acidification. These exceptions are the most frequently tested in exams. When you have an increase in CO2 in the ocean, this CO2, you know, it undergoes pressure, it enters the water and then you have an accumulation of CO2, an accumulation of CO2. You have, for example, calcium carbonate CO3, which is part of the limestone in corals. When I have a lot, a lot, a lot of CO2 there, a lot of acid, this CO2 enters the water, it starts to capture hydrogen from the water. Water, right? So it starts capturing this CO2, it starts acidifying, and I accumulate a lot of H+, I accumulate a lot of H+ here. This H+ that is increasing the acidification, that is, it's acidifying the ocean too much, it goes there and breaks down the limestone of the corals to capture this CO3. So look what happens. The increase of CO2 in the water causes this CO2 to acidify the ocean, forming more and more H+, releasing more and more H+. This H+ causes the decalcification of the corals, right, of the limestone skeleton of the corals, removing CO2 from the limestone skeleton of the corals because of the acidification of the oceans. So H2CO3 can be a big question on your exam because it causes acidification, right? It's part of the acidification equation here, right? In this case, it's CO2 that causes it, right? At least CO2 causes the greenhouse effect and causes the acidification of the oceans. Don't confuse H with CO2.

[00:58:30]Coral bleaching: there's a difference between acidification and bleaching. Acidification is when there's an increase in CO2, and this increased CO2 acidifies the environment, causing structures to break down. It ends up breaking the limestone structures of the corals because it's being decalcified. This is caused by acidification. Bleaching, on the other hand, is caused by increased temperature. When you raise the ocean temperature, it leads, for example, to the expulsion of the mutualistic relationship between the algae near the corals, called anthellae.

[00:59:01]When the temperature increases, they become very stressed and tend to leave the corals, and then they no longer provide food for the corals because they performed photosynthesis near the corals.

[00:59:09]So, the increase in temperature causes coral bleaching because they lose the pigmentation that came from the anthellae. These are the algae that form mutualistic associations with the corals. This is more of a biology lesson, but it touches on a bit of chemistry here. It's theory... Huh? It's theory. Anyway, back to our question. The question asks us the following: "We understand acids and bases, right?" "Look, we understand acids and bases to understand what a salt is." What is a salt? Well, a salt is nothing more than a compound formed from an acid and a base, that is, from a neutralization reaction. When I do a neutralization reaction, I have a compound called a salt, okay? I can have total neutralization or I can have partial neutralization. So, when I take a salt, and the idea of ​​salt in the ENEM exam is for you to be able to identify how it is formed, that is, which acid it came from and which base it came from, okay?

[01:00:08]Getting the idea right. So, within the idea, you are able to grasp the following point of view. If I have a salt like NaCl, I can classify this salt as a basic salt, an acidic salt, or a neutral salt. To classify this salt as basic, acidic, or neutral, I just have to think about which side of the pH it will tend towards. Imagine the following: if I have a strong acid and a strong base, the strong acid neutralizes the strong base. So the salt is... Neutral. Now, if I have a strong acid and a weak base here, the strong acid will pull towards it. So I end up forming a salt with an acidic character.

[01:00:51]If I have a weak acid and a strong base, the strong base will pull this salt towards the strong side, towards the base side, and then I end up with a basic salt. So, the important thing for you to understand here is the big point now and the great nuance of the Dain test. Generally, when we want to correct a soil, when we want to change the pH, we never use acids or bases.

[01:01:18]We actually use salts because they present a slightly acidic character with a slightly basic character. When we think about correcting a pH without being drastic, if you use an acid directly, you will damage or harm or lower the pH too much when you use an acid directly. So the idea is to use a salt that has some character to slightly modify the way things react, but I don't even want you to know this, the practical applicability of things.

[01:01:52]Okay? In the case of our question, look at the nuance of the matter. It says the following, Okay, so you have a vegetable garden. The soil analysis revealed that it's excessively acidic. To fix this, you'll use a salt, because this salt reacts with water and you can adjust the pH. You're not going to throw a base directly in there. You're not going to throw, for example, sodium hydroxide. Remember that sodium hydroxide is even dangerous, right? When we handle it in class, right? Nobody's going to just throw sodium hydroxide directly onto the vegetables to correct it. It doesn't make any sense. The idea is to use a salt that has the characteristic of being able to correct it. Let's understand this then. If I have a place, a soil that is excessively acidic, I need a salt to correct this pH. I need a salt to correct an acidic pH. I need a basic salt. The big question here is: Which of these salts are basic?

[01:02:49]Which basic salt would you choose to correct the pH? Which one would you mark?

[01:03:02]Well, let's think about it this way. To know which salt you would mark, you need to know which acid and which base were formed. When we think about NaCl, is it a neutral acid, basic, or acidic? It's a neutral acid. Why? Because it comes from a strong acid; you put Cl and then H in front. That's the acid it came from, HCl. You put Na and then the hydroxide. That's the base it came from. This forms NaOH for us. This is neutral.

[01:03:35]Okay? Why? Because it comes from a strong acid, okay? And it comes from a strong base.

[01:03:43]Great. Now look, NH4NO3, it comes here as NH4OH, plus HNO3, forming NH4NO3 for us, without knowing how to write the equations.

[01:04:04]Now, look, OH is a weak base for us, okay? So here we have a weak base.

[01:04:15]And here we have a strong acid.

[01:04:19]A strong acid with a weak base forms an acidic salt. So this salt has a character of It's an acidic type. It would make the soil increasingly acidic. I want an acid that is basic. I don't want an acid that is acidic. In other words, I don't want a salt that is acidic. I need to reduce the excessive acidity, okay?

[01:04:46]KBR comes from KOH, which is a base, and HBr, which is an acid, forming KBR, which is a neutral salt because it comes from a strong base, okay? And it comes from a strong acid.

[01:05:10]So I have complete neutralization.

[01:05:13]Now look at this one that many of you underestimated, because what is this? It's an organic salt. What does it come from?

[01:05:21]It comes from CO₂H₅OH, which is nothing more than what, guys?

[01:05:28]What do I have here?

[01:05:32]If you remember, I have three oxygens there, right? Plus one here, plus one here. It comes from a carboxylic acid, right? This is our ethanoic acid, right? Or acetic acid, vinegar, right? It has an acidic character and it... This comes from a base, NaOH, which forms that famous compound, right? When we're larger, we have the chain that leads to the saponification reaction, right? I put C here bonded to C bonded to O bonded here now to an O, right? In A, forming water, right? Look. And here I form precisely a salt of basic character.

[01:06:15]Why? Because I have a strong base.

[01:06:18]And remember, all organic acids are weak.

[01:06:23]All organic acids are weak, right? They are much weaker than inorganic acids. So, the acids there, for example, when we look at the organic functions, right, the carboxylic acids are weak, phenol is weak, sulfur acids are also weak, right? Inorganic acids are those that present the greatest potential for acidity. Organic acids are the weakest acids. Okay? And here to finish, we have, look, once again here, we have NH4OH + H2SO4, right? In this In this case, we have two formulas forming NH4 2SO4, right, being formed here. In this case, I have once again an acid here, a weak base, and I have a strong acid here.

[01:07:16]So I have a salt of acidic character because it leans towards the acidic side. With this template, we have our only salt of the basic type. Okay? That's great.

[01:07:32]Let's go. One more. Look how cool this is to finish. It says the following: cassava tolerates and even prefers acidic soils. An ideal pH between 5 and 5.5. In this range, exchangeable aluminum remains complexed and the plant absorbs nutrients well. A producer received an area of ​​alkaline soil with a pH of 7.8, a light and whitish surface, typical of excess carbohydrates, that is, a basic pH in that soil and unsuitable for planting. He needs an input that acidifies the soil and that can be applied directly to the crop with operational safety and gradual release without risk of burning the roots or immediate waste disposal at the cooperative. Given there, what What is the product indicated to correct the soil pH, making cassava cultivation viable?

[01:08:17]Looking at the graph here, I need a compound that has an acidic character, right? And that can correct the soil without damaging the crop. Let's think about it. ACL, just by looking at it, you already remember that it's a type N compound. Which one would you mark here?

[01:08:36]CCO3, if you remember correctly, where does CCO3 come from? It comes from NaOH plus H2CO3, right? So here I have a compound with a basic character, right?

[01:08:51]Look, it will form a compound with a basic character, right? It will form a basic salt here for us. If I take NO3 here, it comes from NaOH plus HNO3.

[01:09:03]So here I will have a compound with an acidic character, because I have here, oops, with a neutral character, right? With a neutral character, because I have a strong base and a strong acid. We are left with two compounds here, one that is truly an acid and the other that is a salt. But look, this one here, the acid HNO3, It is extremely corrosive, meaning it would burn the crops and damage plant roots. Now, NH4S4 is a salt, a fertilizer; it releases nitrogen into the soil as a nutrient, and it can also reduce the pH because it contains a compound derived from a weak base and a strong acid. So it's a strong acid, reduces the pH, and also serves as a nutrient. Therefore, the answer would be three for us. Guys, this is all you need to understand to get any inorganic chemistry question right on the ENEM exam.

[01:10:06]You don't have to worry about nomenclature or "a" or "a" or "a" and "b" and "b".

[01:10:10]No, no. You need to know how to classify. Review this, look for more ENEM questions on this, research inorganic chemistry questions from the ENEM exam. You'll see that they basically revolve around knowing what type of oxide it is, the base, which ones are acids, the salt, which salt is acidic, which salt is basic—knowing this classification. The initial foundation, guys, is what determines if you'll get the ENEM questions right. Look, we're just at the beginning, folks. If you liked this live stream, leave a like and comment on what you thought of it. There's another one on Saturday and another next week.

[01:10:49]Next week I want to do a basic introductory review, guys. I 'll be gradually increasing the levels, okay?

[01:10:55]So, this month we're focused on filling in the gaps. So, I'm focusing only on the basics first, okay? So I'm focusing on the foundation. In the coming weeks, in the coming months, we'll start bringing more specific content. So if you want classes on thermochemistry, chemical equilibrium, electrochemistry, genetics, physiology, more advanced inorganic chemistry, from this month that we covered the basics until the ENEM, we'll start bringing more advanced content here. So that's why you have to follow all the classes.

[01:11:24]I'm building your basic foundation, reviewing some concepts so I can bring the specific classes here as well. And then, the only thing that All you need to do is like and comment on what you think of our classes and reviews. Deal?

[01:11:39]Thank you so much for your participation.

[01:11:41]We're in this together. Maybe tomorrow afternoon I'll do a live stream here, right? 2 PM, maybe I'll do decomposition, solutions, right? Keep an eye out.

[01:11:49]Maybe something will come out here at 2 PM. Otherwise, on Saturday at 9 AM there's an equations class here on the channel, okay? Stay tuned, keep watching because we'll continue doing review live streams until the ENEM exam. We 'll follow the rhythm of the content, reviewing the basics, then moving on to more advanced content and bringing high-level classes, okay? Thanks, everyone. We're in this together. Until next time. Yeah.