Common types of chemical reactions, that's what we'll be talking about in this lesson from my high school chemistry playlist. Now we're in a whole chapter on chemical reactions. We just finished a lesson on balancing chemical reactions, and after this lesson, we're going to focus a little and spend a little more time on two of the major types of chemical reactions, the oxidation-reduction reactions and the double-replacement reactions.
Now if this is your first time to the channel, my name is Chad, and I'm here to make science both understandable as well as enjoyable. Now this is my high school chemistry playlist, and I'll be releasing these lessons weekly throughout the 2020-2021 school year. So if you don't want to miss one, subscribe to the channel, click the bell notifications, you'll be notified every time I release one. All right, so these are pretty much the most common types of chemical reactions. Combination, decomposition, combustion, oxidation reduction, often called redox reactions for short, single replacement, and double replacement.
Now, One thing to note, these are not mutually exclusive. So like oxidation reduction reactions are kind of a big broader class. All combustion reactions are going to be a type of redox reaction, it turns out. And then all single replacement reactions will also be a type of redox reaction as well. So they're not necessarily mutually exclusive.
And also like under this double replacement, we'll do a whole lesson on these at the end of this chapter. And we'll have, you know, certain types like precipitation reactions are a type of double replacement reaction. So...
Notice they didn't make the list here because they're a little more specific type of double replacement reaction. Acid-based neutralizations are often double replacement. We'll see those showing up in that lesson as well. So you might be like, Chad, these aren't all the different types of reactions. You're right, they're not.
These are the most common kind of larger classes of reactions. And some of the smaller ones we'll learn in other places along the way, like under double replacement reactions. All right, so we're going to start with a combination reaction.
And in a combination reaction, very simply, you're going to have usually two elements or compounds or one of each combined to form one substance. So the one on your handout there is that we're going to have sodium combining with oxygen. We'll take solid sodium, oxygen, gas. So in this case, it's already on your study guide there.
So however, we're going to actually even be able to expect you to predict the products. I would even have it be given to you and balance and things of this sort. So In this case, when you mix a metal, and sodium's on the left-hand side of that periodic table, and a non-metal, and oxygen's way over to the right-hand side. So when you mix a metal and a non-metal together, you're going to form an ionic compound.
And in this case, the ionic compound between sodium and oxygen should have this formula right here. And you'd have to be able to predict that. Now, the way you'd predict that is you'd know that sodium, based on where it's located on the periodic table, is plus one.
Oxygen, based on where it's located on the periodic table, is negative two. And so to get a proper ionic compound, the charges should balance. And that's why we needed to put a two here as a subscript for the sodiums. That way the overall charge of the compound is zero. And then from here, we might even expect you to be able to balance it, especially in light of the last lesson we just did.
And the only thing we've got to do to balance this thing is put a two here to balance the sodium. Now we've got to do more than that, don't we? So, cause we got to put just a two here to balance the auctions, which now is going to force us to put a four here to balance the sodiums, just like it shows up.
I guess I should have looked at the handout first. but just like it shows up on your handout. Alright, the next kind of reaction here is a decomposition reaction. So for a decomposition reaction, it's pretty much often the reverse of a combination. So in a decomposition, instead of having two or more things form one thing, now you're going to have one thing turning into two or more things, so as it decomposes, so to speak.
And so the example I've got on your handout there involves calcium carbonate. So calcium carbonate is this guy. And it turns out if you heat calcium carbonate, and often we like to use the triangle delta symbol, technically, instead of viewing it as a triangle, we look at it as the Greek letter capital delta here.
So, but we often use that delta symbol to represent heat. So, and whether you put that there or not, I'm just giving you a little extra detail here. So, but in this case, it turns out when you heat calcium carbonate, it turns into calcium oxide and carbon dioxide gas. And this is not one we'd expect you to predict. typically.
So like with the combination again, if you mix a metal with a nonmetal, both in their elemental form, I can expect you to predict the product and balance the reaction. So over here, if I just say heat calcium carbonate, that's not usually the kind of thing we can expect you to be able to predict these products, FYI. So in this case, I had to tell you what's going to happen here.
And it turns out this one is already balanced. So just as it is, so life is good. It's a one to one to one ratio. But again, you should recognize this as a decomposition reaction, because one substance turns into more than one substance.
You'll also find out that a lot of these occur through the agency of heat. You've got to heat them up to cause them to decompose. You might call this a thermal decomposition and stuff like that. That's just another hint.
But the big key is whether I write the delta symbol here or not, it's one substance turned into more than one substance. So that's decomposing. position. All right, the next one is going to be combustion. So and combustion means like you're burning something.
So and my first question for you might be like, why can't you do combustion on the moon? Why can't you burn anything on the moon? Well, there's no atmosphere on the moon.
And the part of the atmosphere that is needed for combustion is oxygen. So you have to have oxygen gas to do combustion. And that's why you can't do combustion on the moon.
So think about like when you're trying to put a fire out or stuff like that. If if you're told in the lab that somebody's caught on fire and stuff like that. what your teaching assistant might try and do or something like that in a typical college laboratory is we have these big, lovely, long boxes on the wall that have a fire blanket in them.
And you rip that fire blanket out and you wrap the person in that blanket. So, and, you know, usually we think put a blanket on somebody because they're cold. No, put a blanket on somebody because in this case they're on fire. So not because they're cold, because they're super hot. So but in this case, the real deal is that if you put the blanket on them, you're trying to prevent the fire from having access to more fuel, to more oxygen in this case.
So and that's what you're really hoping to accomplish. So same kind of thing. If you've got a fire, some flammable substance in a beaker, often what you're taught to do is just put a watch glass over the beaker.
So and let the fire burn itself out by using up all the oxygen in that beaker and cutting it off from the rest of the supply. So technically, when you put water on something, So water has already been fully combust, kind of like it's fully combusted hydrogen. When you combust hydrogen, it turns into water and it can't combust any further. So, so one, it's already in a fully combustible form, if you will, not usually the way we'd look at it, but it's kind of what's going on. So, and if you put it on top of whatever is burning, it cuts it off from the O2 gas in the air.
And another, you know, just kind of another way of viewing the fact that it's. O2 you need for combustion. So first off, you should realize that in a combustion reaction, you're always going to have oxygen gas, O2 gas as a reactant.
Cool. Now you can combust a whole variety of things. You can combust certain metals and things of a sort like magnesium forms a nice bright flash when you try and burn it and things of a sort.
But the big thing you need to worry about with combustion are what are called hydrocarbons. And from the name, you can tell exactly what they mean. A hydrocarbon contains only hydrogen and carbon. And usually when we talk about combustion in a chemistry context for either college chemistry or high school chemistry, we're specifically talking about the combustion of hydrocarbons. And when you do combustion on a hydrocarbon, it turns out you get the same couple of products.
The fully oxidized form of carbon is carbon dioxide, and the fully oxidized form of hydrogen is water. And depending on what temperature you do this out, it might be water, liquid, or water gas and things of this sort. So there's our lovely products. And so when you're doing combustion of a hydrocarbon, the only thing that's going to be different is which hydrocarbon are you talking about? There are thousands of different hydrocarbons, but your other reactant will always be O2 and your products will always be CO2 and H2O.
Now, the truth is, if you burn something in practice, if you burn a hydrocarbon in practice, well, it turns out you can actually get incomplete combustion. Instead of carbon dioxide gas, you might make carbon monoxide gas, which is really even. highly toxic and poisonous and stuff like that, much more so than carbon dioxide is. So however, on paper, we're only ever going to look at complete combustion, and we won't even say the word complete combustion, but we're only going to ever look at it producing both CO2 and H2O when you do combustion of a hydrocarbon. Now, if we go to balance this thing, so you'll note that oxygen shows up in two places on the product side, and for that reason, it should be the last thing you balance.
But carbon only shows up in one place on both sides, and so I'll balance the carbon first. One, one, done. Okay, that was not so bad.
Now we'll do the hydrons next. And we've got four here, only two here. So we're gonna need a coefficient of two here to make sure those hydrons get balanced.
And now that we've set the coefficients for these two, we can now balance the oxygens. So we've got two O atoms here and two more O atoms here for a total of four. And to get four O atoms on this side, we'll need a coefficient of two in front of O2. And now we've got a balanced combustion reaction.
So- For a combustion reaction, just like it was with the combination reaction, we might expect you a little more out of you here. So if I say combustion of CH4, you should be able to predict that, oh, combustion of CH4 means I'm reacting CH4 with O2 and that my products are CO2 and water, and then be able to balance it from there. So a little more expected of you for combustion. Now, oxidation reduction reactions, and again, technically a combustion reaction is a type of oxidation reduction reaction.
So But an oxidation reduction reaction is a big broader type of chemical reaction. What happens in an oxidation reduction reaction is that electrons are transferred from one species to another. So that's the first thing you should know is an oxidation reduction reaction is an electron transfer reaction. We often use a mnemonic here.
That mnemonic is oil rig to kind of identify a couple of terms. Now, oil rig here stands for oxidation is loss of electrons, reduction is gain of electrons. So because we talk about the two species, the one who loses electrons, is being oxidized and the one that gains the electrons is being reduced. And we'll spend a whole lesson in the next lesson talking about just these oxidation reduction reactions.
We'll spend a little more time on them and so I don't want to get too much into it now but I do have an example on your handout there. So in this case it involves water turning into H2 gas and O2 gas. Alright, and the key is in this case if you start looking at charges or what we call oxidation states, and again we'll get into a whole lesson on this, but you'd find out that hydrogen here has a plus one charge, which technically we'll call oxidation states in a little bit, auctions minus two, but as elements in their elemental forms we'll find out they're both in their zero states, no charges associated with them at all. And so the hallmark of an oxidation reduction reaction is that you're going to have some of these charges, these oxidation states change in the reaction.
And when hydrogen goes from plus one down to zero, it's because he gained negative charges, he gained electrons, so we'd say that he got reduced. Reduction is the gain of electrons. And when oxygen here is going from negative two up to zero, it's because he lost negative charges that he gets more positive.
So because he lost electrons in this case, we'd say he gets oxidized. Oxidation is the loss of electrons. So But that's kind of the hallmark. And so it's a little more to expect of you at this stage. So I just wanted to bring it up and kind of identify how you identify it and stuff.
But again, we're going to spend the entire next lesson talking about these and how we assign these oxidation states and how we recognize these and a whole host of other things associated with them. So we'll definitely spend some more time on these. I just wanted to give you a little more than just simply saying, yeah, these are these and we'll study them later. And, you know, so, but don't worry too much about this now. Just be prepared for a longer lesson on it next.
Now the next kind of reaction is what we call a single replacement reaction or sometimes called a single displacement reaction and it's simply where one element replaces another in a compound. So in this case I've got elemental zinc reacting with copper nitrate so and the zinc is going to replace the copper to form zinc nitrate and that's going to leave copper all alone instead. So we'd either say that zinc replaced copper or zinc displaced copper either way same terminology.
So again whether we call it single replacement or single displacement same thing. Now These single replacement reactions are examples of a type of oxidation reduction reaction. So there are oxidation reduction reactions out there that are not single replacement reactions like that one. So however, every single replacement reaction you're going to look at is going to be an example of an oxidation reduction reaction. So another thing though, is that single replacement reactions are aqueous reactions.
So, and if you notice, we've got the little AQ symbol here for the phase of state. So there's solid liquid gas. Aqueous though means it's in solution and... specifically it's dissolved in water. So when I take a solid piece of zinc and I put it in a solution of copper nitrate, an aqueous solution, a water solution of copper nitrate, so you'll find out that the zinc dissolves into the solution and becomes part of something that is aqueous, that's dissolved in the water.
And the copper comes out of the solution. You can actually see the silvery zinc disappearing and the coppery colored copper coming out of the solution when you actually carry out this reaction. So The single replacement reactions, again, we'll all study, are always going to be oxidation reduction. Then they're also going to be what we call aqueous reactions that are occurring in water.
And we'll see a little bit more of these in the next lesson on oxidation reduction reactions. We will visit these once more because there's a little more knowledge you need regarding these single replacement reactions. All right, the last type of reaction we'll take a look at are called double replacement reactions.
Now, these actually go by a few different names. They can be called, instead of double replacement, they can be called double displacement. And those are the two most common names, double replacement, double displacement. But they can also be called exchange reactions.
We'll see why that is in a minute. And they can also be called metathesis or metathesis, depending on who you talk to, reactions as well. All synonyms for the same thing. So double replacement, double displacement, exchange metathesis.
All possible names for this type of reaction here. And double replacement gets its name for a very easy reason to see. And so typically what you're going to get in a double replacement reaction is you're going to mix two aqueous solutions. So another example of aqueous type of reaction.
You're going to mix two aqueous solutions, either of two ionic compounds and or acids. And they're going to trade partners between cations and anions. So when we write ionic compounds here, we've got cations, positive ions, with negative ions.
Positive ion with negative ion. And we're going to trade partners so that this... positive ion, the mercury here, ends up with this negative ion, the sulfur over here. So, and this negative ion ends up with this positive ion over here.
So they're just going to trade partners. So we call that double replacement here. So, and we'll find out there's a few different types of these. And one of the ones we'll find out is if one of the products you form is a solid in that aqueous reaction.
So that's going to be called a precipitation reaction. One of the more common types of double replacement reaction. Cool.
But we'll have a whole lesson at the end of this chapter on just these double replacement reactions. So probably the most important of the reactions here, only in terms of the amount of time we devote to it. So we'll have a whole lesson on it.
We'll study three different types with precipitation definitely being the first one we take a look at. But we expect a little more out of you. Oftentimes we'll give you double replacement reactions and we'll just give you the reactants. And we'll expect you to be able to predict the products and often to figure out if it's, you know... which type of the double replacement reactions is, like precipitation or acid base or something along those lines.
So two of the reactions we expect a little more out of you. I just want to cover a couple of specific examples, and bottom of your study guide there if you have that in front of you. First one is just involving a combination reaction. It says write a balanced chemical reaction for the combination of elemental aluminum and elemental fluorine.
So first thing is you're supposed to look at elemental aluminum and... Elemental fluorine, fluorine is one of your diatomic, so when we say elemental, you're supposed to know that means F2. So in this case, we want a balanced reaction, so you gotta predict the product and then go back and balance.
Well, in this case, for a combination reaction, again, if it's between a metal and a nonmetal, you're supposed to know, oh, that's gonna form an ionic compound. And so in this case, it's gonna be some combination of aluminum with fluorine. So, and you're supposed to know that based on where it's located on the periodic table, aluminum will have a Plus three charge and fluorine will have a minus one charge and so for a proper ionic formula here those charges should balance out To zero and for that to happen We're gonna have to put a little subscript three here so that we have three Negatively charged fluorines to balance out the one aluminum that has a plus three charge Alright, so there's our proper species And so first thing we had to do is predict the correct products and now that we've done that and get the proper subscripts here for our products It's now about all coefficients, balancing out those coefficients.
And in this case, aluminum looks good so far, but the fluorines, we got a problem. Here they come two by two, here they come three by three. And so first thing we'll do is double this one. That way we've got a nice even number, six fluorines on this side, which will allow us to put a three here to get six here. And then for the two aluminums, we'll put a two here.
And that's our balanced chemical reaction. So again, for a combination reaction, if you're mixing a metal and a nonmetal, you got to predict the product for the correct ionic compound. and then go back through and balance.
Now the second one we wanna take a closer look at that we expect a little more out of you is combustion. And specifically combustion of hydrocarbons. So this was the example we did before, but now we wanna look at the products of the combustion of C3H8. So let's get that right.
So, so C3H8, and if we're doing combustion, you're supposed to know that, okay, that means it's reacting with O2 gas. In this case C3H8 is propane, turns out to be gas. I don't know if I identified that question. I didn't, so it wouldn't be a big deal here. Not something expected of you.
So, but in this case for again, a combustion of a hydrocarbon, you're supposed to know it's the same two products every time, CO2 and H2O. Cool, and then you got to balance. And once again, oxygen should be the last thing you balance because it shows up in two different places on the product side.
And so in this case, we might start with the carbons. We got three on this side. So easiest way would then to put a coefficient of three and get three on that side.
Hydrons next. We've got eight hydrogen atoms on this side. So hydrogen only shows up here.
We'd need a coefficient of four to make sure that we also had eight hydrons on the product side. And now that the coefficients are set over here, we could balance the auctions. Three times two is six. plus another four right there for a total of 10 oxygen atoms, which means we'll need a coefficient of five right here to get a total of 10 oxygen atoms on the reactant side as well.
And this is the combustion of C3H8, which happens to be propane. Now, if you found this lesson helpful, consider giving me a like and a share. Pretty much the best things you can do to support the channel.
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