Types of Chemical Reactions

Let's talk about these five main

types

of

chemical

reactions

, we will see examples of each one and we will learn to differentiate them so that you can observe a

chemical

reaction and classify it, discover what type it is the first reaction we are going to talk about is the reaction of synthesis, they are sometimes called combination

reactions

. Now synthesis is just a fancy word that means to make and that's exactly what happens in a synthesis reaction. A composite is made of simpler materials. Here is an example. Carbon combines with oxygen gas to form. carbon dioxide CO2 what we produce in this reaction is more complex than the two simple things we started with here is another example, we take sodium and chlorine gas cl2 and that makes sodium chloride NAC what we end up with is more complex than the simple things I begin now with a few brief words about the equations that I am using in this lesson.

Some of these equations I'm going to talk about, like this one here, are unbalanced, so there may not be exactly the same number of atoms on both sides. of the equation now it's normally very important to balance the equations, but when we're going to learn about the different

types

of reactions, the equilibrium numbers can be a little distracting, so here I just want you to focus on the elements and how they are formed. rearranging or combining with each other in different ways, that being said, a synthesis reaction is one in which we start with simple materials and put them together to make something more complex.

If we want to represent a synthesis reaction in a more general or generic way, we could say that it looks like this, we have a and b combining to form a here A and B are different elements or they are different compounds that come together to form something more complex, so that is a synthesis reaction, let's move on to a decomposition reaction, it is a kind of The opposite of a synthesis reaction in a synthesis reaction we put things together in a decomposition reaction, a compound is decomposed into simpler compounds or even the elements that make it up, so in this example here we have water H2O and it's breaking down. into hydrogen and oxygen, these are the elements that make it up now in a decomposition reaction, you don't need to break things down to their basic elements, they can also be broken down into simpler compounds, for example, here we have calcium carbonate ca3 and that It decomposes into two simpler compounds CAO and CO2.

It's not that we take this and break it down into just calcium and just carbon and just oxygen, but still, because these are simpler compounds, it's also a decomposition reaction. If we wanted to find a generalized way of writing a decomposition reaction, we could write it like this: AB separates into a plus b, where AB is some kind of compound and a and b are simpler compounds or elements, combustion reactions. Combustion is basically a fancy word for burning and when something burns, what happens is that a compound containing carbon and hydrogen and sometimes oxygen combines with oxygen gas to produce carbon dioxide and water.

Here in my example, CH4, which is the chemical formula of methane, is a type. of natural gas combines with oxygen and forms carbon dioxide and water H2O now we can start with different things in a combustion reaction and as it is said here the compound usually contains carbon and hydrogen so here is another example of a combustion reaction with this begins C3 h8 which is the chemical formula of propane, another type of natural gas and just like in this reaction we combine c38 with O2 and this gives us carbon dioxide and water, so these two reactions are essentially identical except for the amount of carbons and hydrogens in the compound we started with, it turns out that many things we burn, like natural gas, gasoline, diesel, are actually very similar and only differ in the amount of carbons and hydrogens from the cars that They are found in the molecules that form them, so combustion reactions occur. because a wide variety of compounds look quite similar now, as this definition says, sometimes we have oxygen in the compound we are burning.

Here is an example of a combustion reaction that has oxygen. This is the chemical formula of ethanol or ethyl alcohol and you can see that, just like these, it has a lot of carbons and hydrogens, except that it also has oxygen, but that's not a big deal because it burns just like the other two, combining with oxygen and producing CO2 and H2O, so if we wanted to come up with a general way of writing the formula for a combustion reaction, it might look a little like this: We start with something that has carbon and hydrogen and we can have different numbers of carbons and hydrogen, which is why I put there's that this is the generic general equation for the combustion reaction, single replacement reactions break my heart and in a minute you'll see why, in a single replacement reaction, what happens is that an element that starts on its own replaces to another element in a compound. kicking it in and here's an example to show you what I mean, we start with iron Fe which is this element that stands alone and iron combines with ccl2 which is copper chloride.

Okay, so the copper and the chloride combine here, but what happens is the iron kicks. Take out the copper, the CU, so the CU ends up alone and the Fe, the iron takes the place of that compound, so now the iron and CL are now paired. I like to use a dance analogy to explain this and it reminds me. from something that happened all the time in high school, this is what is happening: we have a dance couple, the purple one and the green one, and they are very happy dancing together or at least the purple boy is very happy dancing and then he shows up red and red is like, hey purple, I'm way cooler, get out of the way, I want to dance with green, and then poor purple gets kicked out and red ends up dancing with green, purple ends up just standing against the wall pretending texting pretending to play a game on his cell phone, but you know he's really sad because he just got kicked out of this dance partner, so you'll see that this is exactly what's happening in the single replacement reaction, right?

The iron Fe is like red here, arriving at a dancing pair of Cu and cl starts cu cu ends up alone and then the red iron takes the place that CU had and the iron ends up paired with cl here's one more example of a replacement reaction unique, you can see how this works in CU this case is the red character and CU goes towards a dance partner of AG silver and nitrate ag3 CU starts AG, so AG ends up alone and CU takes the place of AG pairing with NO3, that's how a single replacement reaction occurs and a The generalized reaction for that would look like a, which is the starting element alone plus BC, which is the dance partner and then that gives us B on its own, which is this element that was removed and then a and c end up paired, so that's a single replacement reaction so finally here is the double replacement reaction.

Now I should mention that single and double replacement reactions are also sometimes called single displacement and double displacement in case your teacher in the textbook uses a different term for them, okay so double replacement reactions don't. are. almost as heartbreaking as single replacement reactions, here's why, because in a double replacement reaction what happens is that the positive and negative ions in two compounds simply switch places, no one gets kicked out in a double replacement reaction, In a double replacement reaction it is as if you have two different reactions. couples of dancing couples and the red that used to be with a gray ends up in a green and the purple that used to be with a green ends up in a gray no one gets kicked out no one no one sat against the wall with their cell phones we're just changing dance partners, so here is a chemical equation that shows a double replacement reaction.

We start with ba and cl together and then na and S so4 together and they just change places, so ba ends with s so4 there it is and na ends. Up with cl, there it is, all of these compounds are ionic, meaning we can break them down into the positive and negative ions that make them up, so here the positive ions are in purple and the negative ions are in green. and as you can see, the positive and negative just switch places, so ba2 plus and cl minus were initially paired, but then ba goes and switches, finds a new dance partner, has to find the other negative ion to that the other negative ion here is s so42 minus so ba2 plus and S so42 minus end up together forming baso4 and then the sodium na1 plus has to find the other negative ion which here is CL min us and they end up paired here na1 plus and cl1 minus forming NAC here is another example of a double replacement reaction.

Well, I'll split it into its ions right away and we get this. We start with k+ and BR less paired and ag1 more and n31 less paired and then they just change the positive and negative so k+ goes and finds the other negative ion which here is n31 minus k+ and n31 less they end up together and ag1 plus silver looks for the other ion negative which is br1 minus and ag1 plus and br1 minus end up paired forming AG BR so that is a double replacement reaction and if we wanted to find a general or generic way to explain it we could use this reaction here where we have AB where A and B are paired plus CD where C and D are paired and then they change partners to give us d and BC, so it's a double replacement reaction, so these are our five main types of chemical reactions in synthesis. simple things combine to make something more complex in decomposition, something complex breaks into simpler pieces in combustion a The compound containing carbon, hydrogen, and sometimes oxygen, combines with oxygen gas to produce carbon dioxide and water.

Single replacement and double replacement are our two Dance Floor reactions in single replacement, an element that on its own combines with two elements that are paired, kicks one of those elements out so that element ends up alone and then that element takes its place in double replacement. It's like two dancing couples where the partners simply swap places A and B and C and D start paired and then A and D finish. together and B and C end up together, so those are the main types of chemical reactions. In the next video we'll do some practice problems so you can see a bunch of different reactions and find out what type they are.