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Video transcript

- [Instructor] In this video, let's try to solve some problems on identifying different types of chemical reactions. So this is my first problem. I have been given four chemical reactions and I have to identify them as combination reaction, decomposition, displacement and double displacement reaction. So before I solve this for you, why don't you pause the video and try it to yourself? Now, if you have tried it, let's see. Let me first of all hide the cushion, so that I have some space to write over here, okay? Now, the first reaction. Here I have iron sulfate on the reactant side and on the product side, I'm getting iron oxide, sulfur dioxide and sulfur trioxide. So I can notice that I have one reactant and I have multiple products. So over here I see that one reactant is breaking down or decomposing into multiple products. And that is an example of decomposition reaction. Decomposition reaction. In decomposition, one reactant break downs into multiple products. Now, let's look at the another one. Over here, I see that I have hydrogen and oxygen on the reactant side and on the product side, I'm getting water, H2O. So I notice over here that I have multiple reactants, but only one, single product. So we can say that here, the reactants are combining to give me one, single product. And this is an example of combination reaction. Let's write it down, combination reaction. In combination, multiple reactants combined to give us one, single product. Let's look at the third question. So here I have iron and copper sulfate on the reactant side and on the product side, I'm getting iron sulfate and copper. So I can notice over here that iron was alone, previously and copper was in its sulfate form, but later on, iron is taking the place of copper and is forming the sulfate and copper is left alone. So I can see that iron is displacing copper from a sulfate and forming iron sulfate and this kind of reactions are called displacement reactions. Displacement reactions where one more reactive element displaces another one from its compound. Now, let's look at the last part. Barium chloride plus hydrogen sulfate gives me barium sulfate plus hydrogen chloride. So I can notice over here that, you know, barium was initially combined with chlorine and hydrogen was initially with sulfate, but later on what is happening that barium is switching places, is getting combined with sulfate and similarly, hydrogen is switching places, it is getting combined with chlorine. Barium forms barium sulfate and hydrogen forms hydrogen chloride. That means over here in the reactant the ions are exchanging position and whenever that happens we call it a double displacement reaction. A double displacement reaction. In this the ions of the reactants they exchange places. Okay, now with this, let's try to solve another problem. So here I have some reactions and I have to identify them as exothermic or endothermic reactions. Now, before I solve this, why don't you pause the video and give it a try. Now, if you have tried it, let's see. See, in the first reaction, iron sulfate is decomposing into multiple products. Now, if you do not remember the actual experiment, it will be hard for you to tell whether this is endothermic or exothermic reaction, but we have a trick. See, we know that this a decomposition reaction and we have also seen that in general, decomposition reactions require more energy to even start, to break down, right? And we know that reactions that require more energy are called endothermic reactions. So in that case, I'm going to guess that this reaction is going to be endothermic in nature. And that will be a correct guess, because, you know, when you're doing the actual experiment, you will have to heat up iron sulfate and then only it will decompose. And you wouldn't get any heat or light in this experiment that's why this is endothermic reaction. Now, if you are wondering now, how do I remember that, you know, decomposition reactions are endothermic generally? So with this I used the magnet analogy. See, when two magnets are stack and I have to pull them apart, I need to provide an energy, right? Similarly, when atoms are stack in a molecule and I want to, you know, separate them, I need to provide energy. And same thing is happening over here there is a big molecule and I want to pull apart some atoms then only I'll get multiple products right. So for this, I have to supply in more energy and that's why endothermic. And again, this is not the reality. In reality, many more things are also happening, but this is a good memory you have to remember that decomposition reactions in general, are endothermic in nature. Okay, now let's move on to the next one. So here I have hydrogen plus oxygen this gives me water. So this is a combination reaction. And we also see that it's written plus heat on the product side. Now, this symbolizes that heat is being released along with the products. Now, since it's already given to us that heat is being released, then we can guess that or we can tell that this is an exothermic reaction. In exothermic reactions, heat is released. This is exothermic reaction. And if plus heat wasn't written, then I could have also taken a guess. See, this is a combination reaction. And generally in combination reactions, heat is released. Now, for this also I have a magnet analogy to remember this. See, here, when two magnets that are attracting, they come close together, then they release sound energy. Similarly, when two atoms, when they're attracting each other, they come close then they release energy. Similarly over here you can see that, you know, hydrogen and oxygen are kind of combining, right? And that's why they will release energy which means that they will be exothermic reaction. Now again, in reality many things are happening over here so this is just a memory aid to help you remember that combination reactions, in general will be exothermic in nature. Now, let's solve the last part, respiration. Now see, this is the process by which are cells break down glucose and in the process we gain a lot of energy which we can use to run and play and do all sort of activities. And that's why respiration is an important process for our bodies. Now see, since this process is giving out more energy, we call this process as exothermic. This is going to be exothermic process. Now, with this done, let's do one last problem. So this is the last reaction. In this one, we have to identify which element is going under oxidation and which is going under reduction reaction. So why don't you pause the video first and try this by yourself? Now, if you have tried it, let's see. First of all let's try recall what do we mean by oxidation and reduction? So see, as the name suggests, oxidation means oxygen's addition. Meaning, if any reaction oxygen is getting added to an element or if in terms of hydrogen we will say, opposite. Hydrogen is getting removed from an element then that element is going under oxidation. If you have to talk about reduction, so that will be opposite. In reduction, if oxygen is removed from an element or hydrogen is getting added to an element, then we will say that, that element is going under reduction reaction. Now with this, let's try to see what is going under oxidation and reduction here. So here I see that hydrogen was alone at first, but after the reaction hydrogen is combined with oxygen that means that oxygen got added to hydrogen. That means hydrogen element is going under oxidation. Oxidation was added to it. Whereas, if you see oxygen, oxygen was alone to begin with, but after the reaction it's added with hydrogen that means hydrogen got added to oxygen. So oxygen must have gone under reduction reaction. Reduction reaction, because hydrogen is getting added. And in this reaction, since both oxidation and reduction are happening, this is an example of redox reaction. Now with this, we have seen all types of reactions and we have also applied them in various examples.