now in this video we're going to talk about how to identify the different types of chemical reactions so the first type of chemical reaction that you need to be familiar with is something called a combustion reaction in a combustion reaction something is typically burning and it releases a lot of heat energy so for example let's say if we react octane which can be found in gasoline with oxygen octane produces carbon dioxide and water when it reacts with air now co2 is a gas water it's a gas at high temperature at normal temperatures it's a liquid but because in a combustion reaction a lot of heat is being generated typically what is going to be in a vapor phase so this reaction generates a lot of heat and also produce a lot of gas molecules which expand at high temperature and all that energy can be used to move pistons and can drive a car forward and so combustion reactions are very useful for generating a lot of heat here's another example of a combustion reaction let's say if we react ethanol which is found in alcohol products if we react with oxygen it's going to produce the same thing carbon dioxide and water so you can easily identify a combustion reaction just by looking at the products if you see co2 and water as products you know it's a combustion reaction on the left typically you'll have a hydrocarbon which is a molecule made up of carbon and hydrogen or sometimes there might be some oxygen there too but the end result is the same you have some hydrocarbon reacting with the oxygen gas in air and it produces carbon dioxide and water so those are the main features of a combustion reaction the next kind of reaction that you need to know is known as a synthesis reaction also called a combination reaction so what are some features of this reaction how can we identify in a synthesis reaction or combination reaction typically you're combining two smaller things to make something larger it can be an element reacting with an element to produce a compound or you can have two compounds coming together to form a larger compound but the idea is you're taking two small things and combine it into something larger and so you're producing something you're synthesizing it well basically you're just combining a and b to make a b and that way you can see it's a combination reaction either case you're building something more complex so what are some examples of a combination reaction let's say if you react in magnesium with oxygen gas this will create magnesium oxide so here we have a pure element magnesium reacting with another pure element to make a compound so that's one example now these reactions are unbalanced i'm not going to focus on a balancing reactions i want to focus on identifying the type of reaction so as you'll see i'm not going to balance the majority of these reactions another example of a synthesis reaction is this one let's say if we have magnesium oxide and we react it with carbon dioxide gas magnesium oxide is a solid by the way and the same is true for magnesium metal there's solids so if you react a metal oxide like magnesium oxide with carbon dioxide it could form into another larger compound magnesium carbonate so both examples are synthesis reactions so here we have a small compound reacting with another small compound to form a more complex larger compound so that's a combination reaction the next type of reaction that we need to talk about is called decomposition so when you hear the word decomposition what do you think of a decomposition reaction is simply the reverse of a synthesis or combination reaction you're decomposing you're taking something larger or complex and breaking it down into smaller components so let's say if you have a product or i mean a reactant a b you're going to break it down into a plus b in a synthesis reaction it's the opposite of that in the synthesis you want to combine a and b to form a larger compound a b so just think of a decomposition as the reverse of a synthesis or a combination reaction so what are some examples of a decomposition reaction now we talked about forming magnesium carbonate but it turns out that if you have a metal carbonate and if you add heat to it you can get the metal oxide back heat will cause the volatile element which is uh co2 it's going to cause the volatile component of magnesium carbonate to escape into the air so when you add heat you're going to cause the gas to leave the magnesium carbonate system so heat will drive away co2 here's another example let's say if you have mercury oxide and if you add heat to it any volatile component in this compound will leave so this will create liquid mercury which is a metal and it's going to generate oxygen gas which is going to leave especially if you heat it up too another example of a decomposition reaction is water if you add electricity to water if you run an electric current through it it can decompose into hydrogen gas and oxygen gas so that's a decomposition reaction so in a decomposition reaction you could take a complex compound and break it up into two smaller compounds or you can take a compound and decompose it into two simpler elements so that's a decomposition reaction and here is the general equation for it a b turns into a plus b now let's say if we have a metal hydroxide in this case calcium hydroxide what do you think is going to happen if we had heat to it if you add heat to calcium hydroxide very similar to magnesium carbonate anything that's volatile will leave the reactant this is going to produce calcium oxide and water vapor if the temperature is higher than 100 degrees celsius water is going to be in its vapor form it's going to be a gas if it's lower than 100 then it could still be in its liquid form so let's say if we have the reverse reaction if we react magnesium oxide with water this can produce magnesium hydroxide now which one is rather what kind of reactions do we have here the first one is it a combustion reaction is it a synthesis reaction or is it a decomposition reaction so the first one we can call this a b and it turns into a plus b so therefore this is a decomposition reaction now looking at the second example we have two compounds turning into a larger compound and that's the general structure of a synthesis or a combination reaction so the first reaction is a decomposition and the second reaction where magnesium oxide reacts with water to produce magnesium hydroxide that's a synthesis reaction now the next type of reaction that we need to talk about is the single replacement reaction this is also known as a single displacement reaction so here's the general equation for this reaction a reacts with b plus c so a is a pure element and reacts with a compound bc and typically a is going to pair up with either b or c if it pairs up with c it's going to kick b out of the solution so now b is a pure element by itself and ac is within a compound so that's the general formula for a single replacement reaction so what are some examples of this let's say if we have zinc metal reacting with a solution of copper chloride which is going to be in the aqueous state so zinc metal is going to replace the copper metal in the solution so zinc is not in the solution it's in its metallic form copper is in a solution so zinc is going to go into the solution and kick out copper which means zinc is going to trade places with the copper so zinc is going to pair up with chlorine and copper has been kicked out so now copper is in its solid metallic form while zinc chloride is now dissolved into the solution so that's an example of a single replacement reaction typically a metal displaces another metal in a solution sometimes it could be a nonmetal displacing another nonmetal in a solution so here's an example let's say if we have elemento bromine which is a liquid in its natural state and it reacts with aqueous sodium iodide in this example bromine is going to pair up with sodium so it's going to displace iodide out of the solution so you're going to have sodium bromide in a solution and elements of iodine out of the solution i2 is a solid at room temperature sometimes a metal can replace another non-metal in this case hydrogen so for example let's say if we have a metal like fe it can displace the hydrogen in hydrochloric acid so fe is going to pair up with cl and it's going to form fe cl2 which is an aqueous state and it's going to displace hydrogen so this is one of those rare examples where a metal displaces a non-metal but for the most part metals tend to replace metals and non-metals tend to displace other non-metals now let's move on to a double replacement reaction in a double replacement reaction also known as a double displacement reaction it differs from a single replacement reaction by this one key fact in a single replacement reaction an element usually reacts with a compound so for example a the element reacts with the compound bc but in a double replacement reaction the compound a b reacts with another compound cd now a is going to pair up with d and b pairs up with c so it's a double replacement so we're going to have a d plus b c and so that's the general type of that's the general formula of a double replacement reaction now there's different types of double replacement reactions you have precipitation reactions you have acid-base neutralization reactions gas evolution reactions just to name a few so for example let's say if we're reacting with silver nitrate which is in the aqueous phase that means it's soluble in water it dissolves in water and let's mix it with sodium chloride which also dissolves in water so that's an aqueous phase if we want to draw the products of this reaction silver is going to pair up with chloride and it's going to form silver chloride which is a white insoluble product so it's a solid silver chloride is an ionic compound that doesn't dissolve in water it's insoluble sodium chloride on the other hand is a soluble compound it dissolves in water so we write aqueous sodium is going to pair up with nitrate and you're going to get sodium nitrate na no3 which is also soluble in water so this is going to be an aqueous phase so this whole thing is known as a double replacement reaction but when you mix two aqueous solutions and if you get a solid product this double replacement reaction now has another name it's called a precipitation reaction so by mixing two aqueous solutions these could be two clear solutions and if you get a solid product that forms if you can see the solid product in the solution then you have a precipitation reaction now here's another example let's say if we mix hydrochloric acid which is an aqueous phase with sodium hydroxide what's going to happen as you can see we have a double replacement reaction we have a compound reacting with another compound hydrogen is going to pair up with hydroxide to form water and water is in a liquid phase sodium is going to pair up with chlorine and you're going to get sodium chloride which is going to be in the aqueous phase so this double replacement reaction has another name hdl is an acid it's hydrochloric acid sodium hydroxide is a base when you mix a strong acid with a strong base you're going to get salt and water sodium chloride is found in table salt this is known as a neutralization reaction particularly an acid-base neutralization reaction you're mixing two aqueous solutions one is an acid one it's a base and you get a neutral water and so so that type of double replacement reaction is an acid-base neutralization reaction so what about this one sodium sulfide in the aqueous state reacts with hydrochloric acid which is also in the aqueous state and it's going to produce so sodium is going to pair up with chlorine to make sodium chloride which is also an aqueous state and then hydrogen is going to react with sulfide to produce h2s hydrosulfuric acid is a gas so this particular type of double replacement reaction when you mix two aqueous solution and you get a gas is known as a gas evolution reaction so that's another type need to be familiar with now what about this one let's say if we have sodium chloride in the aqueous phase and let's say it reacts with potassium nitrate in the aqueous phase now this is another double replacement reaction we have a compound reacting with compound to draw the products sodium is going to pair up with nitrate and it's going to form sodium nitrate which is also soluble and potassium is going to pair up with chlorine or chloride forming kcl which dissolves in water so we mix two aqueous solutions and we still got aqueous products even though this is a double replacement reaction no reaction actually takes place there's no change in phase the only way a reaction takes place is if you get a solid product a liquid product or a gaseous product if everything remains in the aqueous phase no reaction took place so now let's take a brief quiz i'm going to write down a few reactions and i want you to classify each reaction based on the names that we've went over so far so here's the first one let's say if calcium hydroxide is exposed to a heat source and it produces calcium oxide and water what kind of reaction is this is this a single replacement double replacement is it a combination reaction a decomposition reaction is it a combustion reaction which one is it so we have a complex compound on the left and we're breaking it down into two smaller compounds so this is known as a decomposition reaction so now let's move on to the next question so let's say zinc metal reacts with aqueous nickel chloride to produce zinc chloride and nickel metal what type of reaction do we have here so an element a pure element reacts with a compound to produce another compound and a pure element this is known as a single replacement reaction zinc replaced nickel in the reaction so only one replacement actually took place here's another one barium oxide reacts with carbon dioxide to produce barium carbonate so what type of reaction do we have here so we have two compounds joining up together to form a larger compound this is known as a synthesis reaction or a combination reaction so that's the answer for that one now what about when hydrogen peroxide converts into hydrogen gas and oxygen gas what kind of reaction do we have here so we have a compound breaking down into two pure elements this is called a decomposition reaction by the way hydrogen peroxide will naturally do this if it's exposed to air and sunlight it can naturally break down into hydrogen gas and oxygen gas try this one lead nitrate or rather lead to nitrate reacts with sodium chloride to produce lead ii chloride and sodium nitrate lead nitrate is soluble it's an aqueous phase and the same is true for sodium chloride and sodium nitrate lead chloride doesn't dissolve in water it's insoluble so what we have here is two aqueous solutions mixed in to form a solid product so notice that lead paired up with chlorine to form lead to chloride nitrate paired up with sodium to form sodium nitrate so this is a double replacement reaction in this example lead replace nitrate to pair up with chlorine and sodium replace chlorine to pair up with nitrate so we have a double replacement going on here and as we can see you can also see this way we have a compound a b which is lead nitrate it reacts with another compound cd that's sodium chloride to produce so a got together with d to form a d that's lead chloride and the two in the middle b and c got together to form uh bc or in this case actually cb where c is for sodium and so whenever you see that general reaction you know it's a double replacement reaction or you can call it a double displacement reaction if your textbook uses that term so that's a quick way to identify you have a compound reacting with another compound now there's another name for this double replacement reaction whenever you mix two aqueous solutions and if you get a solid product that forms this double replacement reaction is also called a precipitation reaction so that's another name for it now what about this reaction chlorine reacts with sodium bromide to form sodium chloride and bromine chlorine is a gas bromine is a red liquid sodium bromide and sodium chloride dissolve in the solution what kind of reaction do we have here so we have a pure element which is chlorine and it reacts with a compound sodium bromide when you see that you know it's a single replacement reaction by the way all single replacement reactions are redox reactions and all combustion reactions are redox reactions a redox reaction is a reaction where you have a transfer of electrons you have oxidation which is a loss of electrons and reduction which is a gain of electrons we won't go into it much but i just want to let you know that all single replacement reactions are redox and all combustion reactions are redox a double replacement reaction is never a redox reaction now as for decomposition reactions and synthesis reactions if you have let's say in a decomposition reaction a compound break it down into pure elements then it's a redox reaction and the reverse is true and the synthesis reaction if you have two pure elements combining to form a compound it's a redox reaction now if you have a large compound breaking into two smaller compounds in a decomposition reaction chances are it's probably not a redox reaction and the reverse is true for a combination reaction if you have two smaller compounds reacting to form a larger compound chances are it's not a redox reaction so that's for those of you who are also studying redox reactions if you need to know that so now let's get back to this a plus bc so a is going to pair up with c in this case rather a pairs up with b b is uh sodium and a is chlorine so here we have ba and then c is by itself so in this example we have a non-metal displacing another nonmetal in the solution so chlorine displaces bromine and chlorine pairs up with sodium to form sodium chloride so that's a single replacement reaction now what about this one methane also known as natural gas reacts with oxygen gas to produce carbon dioxide and water what type of reaction do we have here anytime you see co2 and water and if you have a hydrocarbon on the left this is a combustion reaction which is also a redox reaction now what about this one potassium chlorate is exposed to heat and then it forms potassium chloride and oxygen gas what type of reaction do we have so here we have a complex compound a b and upon heating it it breaks down to two smaller compounds a and b but in this case b is a pure element and a is a compound so this type of reaction is also a redox reaction anytime you can produce a pure element from a compound it's going to be a redox reaction but this particularly the name that we're looking for is a decomposition reaction we're taking a complex uh compound and we're breaking it down to two smaller components a and b so potassium chlorate is undergoing thermal decomposition to produce oxygen gas and potassium chloride now what about this one sulfuric acid reacts with potassium hydroxide to produce water and sodium sulfate so what kind of reaction do we have here sulfuric acid is an aqueous phase and the same is true for potassium hydroxide they're dissolved in water and water is in the liquid phase sodium sulfate is soluble it dissolves in water so it's an aqueous phase sulfuric acid is a compound a b potassium hydroxide is also a compound so we have two compounds reacting with each other this is called a double replacement reaction whenever you have two compounds reacting with each other it's a good indication that you have a double replacement reaction so in this example we can see that hydrogen paired up with hydroxide to produce water so that's a getting together with d to form ad and then potassium pairs up with sulfate and for some reason i wrote sodium sulfate so that's my mistake that was supposed to be potassium sulfate let me just uh put that here k2 so4 that's what the product should have been but it's still a double replacement reaction and so c pairs up with b producing uh cb now there's another name for this type of reaction in addition to being called a double replacement reaction sulfuric acid is a strong acid potassium hydroxide is a strong base these two are getting together to form salt which is potassium sulfate it's a type of cell almost all ionic compounds are considered salts so it's produced in salt and water so this is called an acid-base neutralization reaction so when you mix two aqueous solutions and if you get a liquid product and if this is an acid and this is a base then typically it's going to be an acid-base neutralization reaction now let's move on to our next example magnesium metal reacts with nitrogen gas in the air to form magnesium nitrite perhaps you perform this experiment in class if you take a strip of magnesium metal or one of those magnesium ribbons if you burn it in air it produces this very very bright brilliant light you gotta be careful because uh ultraviolet light also is produced from it and this is the reaction that's happening when you burn magnesium metal in air it can react with the nitrogen gas in air and so it produces magnesium nitride so this type of reaction how would you classify it so we have a pure element magnesium reacting with another pure element nitrogen gas to produce a compound so we have two small things combining to form something that's larger or more complex so this is called a synthesis reaction also known as a combination reaction by the way this particular reaction is it a redox reaction here's a quick and simple technique to know if you have an oxidation reduction reaction also known as a redox reaction if you see a pure element on one side and that same element inside of a compound then for the most part it's a redox reaction so this particular type of synthesis reaction is an oxidation reduction reaction but the answer we'll focus on today is the synthesis reaction or combination reaction now let's say if we have pentane c5h12 and we react it with oxygen gas in the air and it produces carbon dioxide and water so what kind of reaction do we have pentane is a liquid and oxygen co2 and water will be in the gaseous state this reaction releases a lot of energy and so water will most likely be in the vapor phase so kind of reaction do we have so anytime you have a hydrocarbon on the left and if you produce co2 and water on the right then you know you have a combustion reaction so that's the answer now is this reaction a redox reaction is there a transfer of electrons taking place in this reaction notice that oxygen is in its elemental form on the left side but on the right side it's found within a compound so just by looking at this you can see that this is also a redox reaction it's an oxidation reduction reaction so all combustion reactions are redox reactions now what about this one let's say if we have sulfurous acid and upon heating it it turns into liquid water and sulfur dioxide which is a non-metal oxide and it's also a gas and this is an aqueous phase what kind of reaction do we have here so this is a decomposition reaction so we have a complex compound a b and it's breaking down into two smaller compounds so it's a decomp reaction now this particular decomposition reaction is it a redox reaction notice that we have no pure elements on any side of the reaction all the elements are in the form of a compound and when you see this typically this is not a redox reaction if there's no pure elements anywhere chances are it's not a redox now let's move on to our next example we're going to react sodium bicarbonate with hydrochloric acid and in this reaction we're going to get sodium chloride water and co2 so these two are in the aqueous phase water is in the liquid phase and co2 is in a gas phase so how would you classify this reaction and have you seen anything like this it turns out that there's multiple classifications for this reaction because there's a lot that's happening first and foremost we're mixing two aqueous solutions and we are getting a gaseous product when you see that you can classify it as a gas evolution reaction at the same time sodium bicarbonate can act as a weak base and hydrochloric acid is a strong acid and we do get water which is a feature of an acid-base neutralization reaction now before we get water and carbon dioxide we get something else so when we react sodium bicarbonate which is also called sodium hydrogen carbonate with hdl initially you could think of this as a double replacement reaction sodium is going to pair up with chlorine to form sodium chloride and hydrogen pairs up with hco3 bicarbonate to produce carbonic acid so if you view it this way this appears to be a double replacement reaction i wrote that wrong a b reacts with cd to produce ad and cb so the first step is a double replacement reaction now the second step carbonic acid it's unstable it's an intermediate and it breaks down into water and carbon dioxide the two things that we see here so the second step is a decomposition reaction but overall you could think of it as a gas evolution reaction because we do get a gas by mixing two aqueous solutions so as you can see there's multiple classifications for this type of reaction it's a complex reaction now let's review the main types of reactions that we've went over so far so if you have a compound a b and you break it up into two smaller components this is known as a decomposition reaction so i'm going to write d comp for short now the reverse of a decomposition reaction let's say if you mix two small components and get a larger component this is known as a synthesis reaction or you can call it a combination reaction if you react an element with a compound then these two will switch places a is going to pair up with c kick out b this is known as a single replacement reaction and if you react two compounds together this is called a double replacement reaction and there's three types of double replacement reactions you have precipitation reactions which occur when mixing two aqueous solutions to form a solid product you have an acid-base neutralization reaction when you mix an acid and base you get liquid water and the salt and then you have the gas evolution reactions where you mix two aqueous solutions and you get a gaseous product and finally combustion so typically you'll have some hydrocarbon and may have oxygen with it it reacts with oxygen in the air to produce co2 and water so that's a combustion reaction so those are the main types of reactions that you need to be aware of thanks for watching you