 Hey everybody, welcome to Tutor Terrific. I have for you here basically a part three of my basic reactions video This is a video on double replacement reactions the fifth of the five reaction types This might be the most complicated Reactions to complete but it is very important as a high school chemist to understand how to do this or if you're going Into college chemistry you really got to have this down So we're going to analyze double replacement reactions today first I want to point out the reactions model here. We have two compounds two compounds combining in The double replacement reaction. I'll talk about these little subscripts here in a second So you've got a compound AB what's going to combine with the compound CD and if the reaction occurs it will yield a Compound AD plus compound CB now Let me explain what happens in a double replacement the two cations switch anion partners A good analogy for this would be like this TLC show wife swap where two wives exchange Husbands for a certain amount of time and learn how to Appreciate their own husbands when they go back to their Home family. It's quite an interesting show. I don't know if I agree with it, but it's quite entertaining So imagine a and B and C are the wives and they literally swap husbands so Do not miss mix up the order of anions and cations when you do this a And see our cations so they need to remain first when the partners are switched See how a and C are still in the first slots in those compounds and B and D remain last So the easiest way to do this would just be to switch anions really and as you could see that's what's done here now the reaction occurs if a Certain type of product results now Let me go over the key before I get into that the key here tells us this new set of subscripts that we have to be adding to our Compounds on both the reactants and the product side so a queue stands for aqueous which means It's dissolved in water now one thing I haven't told you yet is that a lot of these double replacement reactions occur with water as a Solvent so there these things are dissolved in water and a queue. That's literally what that means It's aqueous which means it's in water solution s in parentheses is reserved means solids specifically but What we use it for in double replacement reactions is when Something is not soluble in water that's formed in the reaction and that is called specifically a precipitate reaction and a precipitate forms And it literally is visible After maybe two clear liquids are mixed together. You see this milky substance or this yellow substance in some cases And it's quite seems like magic, but it's you're just forming something that's not soluble in water And so it Dissolves out of solution as a precipitate. That's what it's called. G is reserved for gas So if one of your products happens to be a gas It will literally bubble out of the solution and that means it's not soluble in water also And it will create bubbles like hydrogen gas for example That's just one example And then L liquid. So if we have two liquids that do not mix A liquid that doesn't mix with water will separate out a solution such as for example oil does not mix with water We're not going to deal specifically with G or L as much as we are with s But what I want you to understand is that a double replacement reaction generally occurs only if There is an s g or L so a solid gas or liquid that does not dissolve in water that is formed if The two products are both aqueous in Solution that means normally the reaction will not occur That's something that you don't always hear in your high school classes, but it is true now one more thing before I Move on. How do you tell if something is aqueous or not? Well, you use a solubility chart Or the solubility rules and I have that right here I'm just gonna move this closer to the camera so you can see in the top to have the basic solubility rules that all Maybe your parents or your older compadres had to learn this way We didn't really have the charts like you guys do So if you look at this there are about seven rules the first two rules tell you what's always soluble in water So any cations? Lithium sodium potassium rubidium CCM and Francium those are all the group one elements and ammonium So any compounds you make with those are actually soluble so when those are the cations no matter what the anions are is soluble Now let's continue Rule number two tells us that all these anions all the compounds made with them nitrates chlorates perchlorates and Acetates every single one that you can make with those as anions are soluble as well. So those are Pretty easy rules to remember. They're always soluble. Okay now Rule three is like yeah, that's normally soluble chlorides bromides and iodide. So there's some of the halogens and There are exceptions to this rule and that is notably some bad actors silver lead and mercury Roman numeral one I'm not gonna get too much into why that's called Roman numeral one mercury, but that's what it is Those are not soluble chloride bromide or iodide compounds for sure now rule one is an exception, but carbonates chromates Phosphates and sulfides sulfites excuse me are generally Insoluble, but when they combine with a group one element such as above they are soluble, but other than that They are not. Okay, so we'll watch out for those anions. We usually get insoluble situation or precipitate forming Number five so If we with the exception of rule one and the barium ion hydroxides and sulfides Are insoluble now there's exceptions to that rule two with those group one compounds or ammonium, but generally the hydroxides and sulfides are insoluble in water and then rule two which is about Nitrates chlorides perchlorates and acetates being soluble if we allow that exception generally speaking mercury Roman numeral one silver and lead Salts are insoluble now we saw that already in rule three that they were bad actors They're generally bad actors. They're generally not soluble except when they're combined with Roman rule number two anions then rule seven calcium strontium barium All the sulfates are soluble of those No, excuse me. All sulfates are soluble except for calcium strontium barium and all these guys like silver mercury one and lead two actually that's what led Roman numeral two those are Soluble sulfates so sulfates got a lot of exceptions to it, but most sulfates are soluble now That's a lot to remember and there's actually a song that exists to remember all these. No, thanks There's a nice chart. This is just one example of a super-duper chart that kind of lays this all out for you It lays out the cations right here and the anions up here You'd combine one cation with one anion for example aluminum Chlorate let's say aluminum chloride is one of your Compounds you have to figure out whether it's soluble or not It's soluble on this chart if it has an aq in that box for aluminum chloride for example That has an aq that's soluble if you see an s such as aluminum fluoride for example That's not soluble because you see an s so it would form a precipitate You can see some blanks in here and you can see some lines Those are for ones that don't follow the normal rules. Maybe they don't actually exist or they There's multiple iterations of them and so some are soluble some aren't Maybe some form liquids some form gases But generally speaking a chart like this pretty basic chart, which is definitely not exhaustive In either list by any means Will suffice for your first class chemistry. Okay, so we're going to refer to this chart for sure in my examples Okay, so let's work on these examples. I'll leave the solubility rules there when we need them So what we're gonna do is we're going to first determine What the products will be and we'll assume all of these will occur even if we get two aqueous solutions As products But I want to to determine what the products will be I want you to determine if they're soluble or not And I want you to also charge balance them and then balance the reaction So there's quite a bit to do in these double replacement reactions that we didn't have in the other types of reactions we studied So we've got ca no 3 2 which is calcium nitrate And we've got potassium bromide so If the reaction occurs What's going to happen is calcium and potassium will switch anions. So we will have calcium bromide now Put the bromide with the calcium and put the nitrate with the potassium. So we'll get k and oh three Now we can't just write aq by them because we don't know if they're soluble or not. We have to look at the solubility chart So let me hold this up for you So you can see Let's find calcium bromide. Here's calcium and You go two over you can see bromide and you can see that it's aqueous So that means calcium bromide is soluble. The other one is potassium nitrate potassium way down here you go over to nitrate Which is right here. Oh, that's also soluble. So generally this reaction wouldn't necessarily occur but we're going to assume it does here because just for the sake of balancing these guys and all that getting some practice so technically We've got a reaction that does not favor to occur We'll assume it does and now we're going to balance. Okay, so Calcium and bromine bromine is an halogen group seven So it has a charge of minus one in an ion form Calcium is in group two alkaline earth metals. So it's plus two Uh-oh, we've got a we've got a problem with balancing in order to fix this. I'll have to add a bromine so that I have two bromines So we have cabr two now. We've got a plus two minus two balance Now we got to check potassium and nitrate nitrate is minus one potassium Is plus one you got to memorize these nitrates and all these other polyatomic ions. You got no other charges potassium plus one nitrate minus one. We're good to go the one to one ratio Okay, now that we've looked at the solubility rules. We've uh created the correct products. We need to balance the reaction So let's look at calcium to start from the left and go to the right calcium is one on each side So that's good Nitrogen there are two nitrogens on the reacted side There's only one on the product side. So i'm going to need to double this whole compound in order to address that So obviously you got to affect a few things notably Uh, uh, potassium is now been affected. There are two Potassium's on the product side, but only one on the reactant side. So i'll need to double that Now i have two potassiums and that of course now doubled the number of bromines i have But it made it balanced because two bromines on this side will balance with the two bromines On this side. Okay, let's check everything to make sure everything's balanced. There's one calcium on each side There are two nitrogens on each side There are how many oxygens three times two six On the reactant side And there are two times three six on the product side Then we'll go to the next compound potassium. There are two On the uh reactant side and there's two on the product side Bromine there's two on the reactant side and two on the product side So this reaction if it occurred is now balanced. Okay next We've got sodium hydroxide Combined with iron two chloride iron roman numeral two because it has to be plus two To combine this way with chlorine, which is normally minus one Okay, so if the reaction were to occur we'd get the following products switch the places of the anions Just leave the cations where they are it makes it simple. So we're going to have sodium chloride And we're going to why don't i meet and uh bring the two over because i'm going to uh rebalance By charges anyway, so i don't need to do that the only place where i'd keep the Subscripts is when i have a polyatomic ion like nitrate i'm going to keep the three for the oxygen because that is to do with the anion itself Okay, so there's sodium chloride and the other one will be iron hydroxide okay Now generally these In this stage of the game you're not studying oxidation or reduction reactions And so you're going to assume that the iron will keep the same charge since it's capable of having more than one oxidation number Um, so when you charge balance this keep that in mind, but let's start with sodium and chloride Chlorine is a charge of minus one since it's a halogen Sodium has a charge of plus one because it's a group one metal So one to one ratio. This is charge balanced and over here We have hydroxide again. You got to memorize these OH is minus one charge But iron over here was roman numeral two. So that's two plus it needs to remain two plus Okay, since this is not an ox oxidation reduction reaction We're going to study that a lot later from now. Um, so here we are This is not balanced. We will need actually since this OH is minus one against a plus two iron We're going to need two hydroxide ions. So you got to put that in parentheses because we're increasing the amount of the entire hydroxide um polyatomic ion All right, so now we're charge balanced. Let's check and um, see What these actual compounds are and if they are soluble or insoluble in water Okay, so first we have Sodium chloride. I think you know that's table salt. I know it's soluble, but let's just check the chart sodium Chloride is the fourth one over Yes, aq. So that is uh, excuse me the fifth one over that is soluble the other one iron hydroxide I don't hold out much hope for that Because a lot of the hydroxides are insoluble iron roman numeral two right there If we go over to hydroxide, oh Not soluble. It's got an s. This is going to form a solid precipitate It um form one of those milky or powdery substances When this reaction occurs So sodium chloride will get an aq And iron hydroxide from numeral two will get an s. So this is a precipitate reaction specifically All right, now let's balance the whole reaction So far so good with sodium one on each side Uh, usually just so you know, it's easiest to save oxygen for last Generally speaking because in some cases like this fourth example, we're going to have oxygens all over the place But here since we only have one example of oxygen on each side, we can balance it now Um, there's one on this side, but there are two because of that two down there on this side So that means we're going to have to double sodium hydroxides concentration and uh because I just messed up the sodium I'm going to go fix that on the other side. So now there's two sodiums on each side So there's two sodiums and two oxygens on each side And uh now I've created a situation where I have two hydrogens on the reactant side But I needed that anyway because I have two hydrogens on the product side All right, so three of the elements are done. We have two left iron One on the reactant side One on the product side remember that little scub scripts those little subscripts only apply to what's directly in front of them And that means inside the parentheses if there's a parentheses Now, um, also Let's look at chlorine. There are two chlorines on the reactant side Voila, there are also two Chlorines on the product side as well So this is fully balanced with those two additions of sub coefficients there Okay, so we saw an example of a reaction that generally is tend uh favor to occur and forms of precipitate Let's look at this next one. We've got lead nitrate romanumeral two lead because it's combining with two NO3s Which are minus one each I don't like that lead. We usually lead is insoluble. Of course by the first, uh, the second rule Lead nitrate is actually soluble Um, potassium chloride That's soluble because it's got a potassium in it. So let's see what happens if we assume this reaction occurs Switching the anions will have lead chloride. I don't hold out much hope for that to be soluble And we've also got potassium nitrate. I hold out a ton of hope that that's soluble Okay, let's charge balance and then we'll check the chart. So lead chloride. Oh my goodness It's lead romanumeral two again. This is not an oxidation reduction reaction. So we assume that stays the same Lead romanumeral two means it's two plus against chlorine, which we've seen before is minus one So we'll need two chlorines to make minus two against a plus two and they balance Uh, potassium is plus one since it's a group one metal and nitrate is minus one Um, need to memorize that. So that's good to go Now, let's uh check the chart So this chart says for lead Most things are insoluble. Uh, we've got lead two here lead to chloride. I Am correct lead to chloride no way in soluble and then we're going to check potassium nitrate just for kicks potassium right here go over to nitrate Uh, definitely soluble all the potassiums are soluble and all the nitrates are soluble So that's like a cross through the chart of acues All right now back to here Lead to chloride is going to get an s and potassium nitrate is going to get an aq So this is going to form a nice Little precipitate. Okay. Let's go ahead and balance the reaction There's one lead on the reactant side. There's one lead on the product side. Good so far Nitrogen. Oh boy. There are two nitrogens on the product reactant side. Oh, there's only one On the product side. So we're going to need to double that Whole compound Continuing let's check oxygen. There are six oxygens three times two on the reactant side and oh, there are three times two reactions Excuse me oxygens on the product side. So that's actually good. I made that balance now. Let's go to potassium k There's only one on the reactant side and two on the product side. I'm going to need to double The kc l potassium chloride compound and then check chlorine now. There's two chlorines here But there's also two chlorines on the product side. So that's good to go all good to go This is completely balanced now All right, let's check this one this one crazy. What's going to happen here? Just got to keep track. There's a lot of oxygens. There's a lot of crazy things by the way NH4 is ammonium Okay, ammonium is not present. Oh, actually it is it is present on this chart I thought it wasn't it is so we can check the solubility chart To see if this reaction forms a precipitate or not um, so Uh, switch the anions. We're going to have ammonium Nitrate now I'm taking away All the parentheses here because we're going to redo that charge balancing. Okay, so h4 to I take that away Just put NH4 With the nitrate and then I'm going to have barium sulfate. Don't hold out a lot of hope for that We'll check the chart Okay, let's charge balance first Ammonium is plus one. Okay, it's plus one and you saw that when I went over rule number one of the solubility rules and Um nitrate as you know by now since we've done it so much It is minus one. So this is a one-to-one ratio. It's good to go barium sulfate now Barium is a group two metal and so it is plus two And sulfate is a minus two chart again. You have to memorize that So this is actually good to go as well. It's plus two against minus two. Now. Let's check the solubility chart See if a precipitate forms or something else If you look at the chart ammonium nitrate is soluble, so that's aqueous and Barium sulfate here we go across your fingers barium Scoot all the way over to sulfate Nope, that is insoluble So another precipitate reaction here I'm curious to see what colors actually come out of this if you're to do these, but I'm sure you can find videos online to So yourself check it out So put an s by the barium sulfate. Okay, so let's go ahead and check this and see What we can do here to balance the whole reaction. It's going to be a little tricky, okay we've got two nitrogens with this particular compound, but we have two nitrogens also With the other compounds. So we have four all together on the other side It looks like we only have two since they both Combined with the first product ammonium nitrate. So we're going to need to double that to make four Okay, of course that changed a lot of other things, but let's just go through the list here hydrogen Thankfully only exists in ammonium So there's eight of those here four times two On the reactant side and look on the product side now that I doubled the whole compound There are eight hydrogens two times four on the product side. So that's done Going on we have sulfur next sulfur. There's just one on the Reactant side, but there's also just one on the product side. So that's good to go Then we're going to do barium Remember i'm saving oxygen for last especially here because there's so many of them save it for last Barium, there's just one on the reactant side and there's just one on the product side. So that's good now Let's check oxygen We've got a lot to count. We've got four in the first compound ammonium sulfate and we've got six In the second compound barium nitrate making 10 total 10 total Oxygen's on the reactant side crossing our fingers product side Three times two six plus. Ah, yes four makes 10 total oxygen atoms Wow With just a single two there Everything is balanced All right, I got two more examples that are a little bit More unique than the others So here we have hydrogen chloride and sodium hydroxide. Okay Let's assume it's going to occur And any of you who studied acids and bases before you know, what's going to happen This is a neutralization reaction type double replacement, but let's just do it as normal So, um, switch the anions. So we're going to get um, HOH We need to study that but in a second and then we're going to get sodium and chloride Which we already know Is soluble in water, so that'll be aqueous. But what's HOH? Well, this is going to combine Like this it's going to make water HOH is water Now water is obviously a liquid And it kind of mixes with itself So it's hard to say if it's soluble or not because it's water also and so that gets an L Because it's a liquid in a liquid It's not just for L is not just for liquids that are not insoluble But it's also for water to denote that. Hey, we're not dealing with paper here. We're dealing with liquid water. Okay So let's charge balance this Uh NaCl plus one Minus one for cl. So we already know that's good to go. We know it's soluble. We know water's a liquid Let's balance the whole reaction. So we've got two hydrogens Two hydrogens you've got one chlorine One chlorine we've got one sodium One sodium we have one oxygen One oxygen There you go. Sometimes they're already balanced after you charge balance them. It's not often But in this case, that's how it worked out Now this next one I I really Interesting history with um, we've got sodium cyanide now whenever you see cyanide think death because Most things that are made with cyanide are poisonous. Um, so that's in solution plus hydrogen bromide That's in solution. Uh, let's assume this reaction occurs. What will we make? We will make sodium bromide Sodium bromide changing the anion's positions and we're going to make this lovely little guy h cn hydrogen cyanide um hydrogen cyanide is actually a gas And so it will bubble out of solution and sodium bromide is um Well, let's check Let's go ahead and check that guy The reason I told you about hydrogen cyanide is actually cyanide is not on the list Um, there are many lists that have it but this one does not. Um, so sodium let's go down to sodium and then uh, bromide It's the second one. Uh, it is Um aqueous so that is dissolved in solution So we're not forming precipitate and a gas just a gas So this is one of those situations we have on that bubbles out of solution But you better hope you're on another planet when this does because this stuff is super super poisonous and will kill you So my story behind this is um, I actually saw this reaction somewhere in a textbook when I was in high school chemistry And I asked my wonderful teacher mrs. Tar. So what's gonna? Can we make sodium cyanide and hydrogen bromide together? Um, let's see what happens and she smiled at me and said okay moving on and it was really funny because um She knew and I she knew I had studied it and she knew I knew it was going to make hydrogen cyanide gas And uh, and it was very poisonous. So Just some good memories when you understand what's going on in chemistry. It can be a lot of fun So I hope these videos help you. Thank you guys so much for watching this one until next time. This is falconator signing out