Understanding Neutralization and Reactions

Chem 115 for 2020 lecture on September 25th. Okay, so on Wednesday's lecture, we discussed, we stopped at the neutralization reaction. A typical solution chemical reaction. And the reaction that we used as the example is the reaction between hydrochloric acid solution and sodium hydroxide liquid solution, strong acid. Strong base Reacting with each other and their product of that is acid and base neutralize each other produce water liquid and Assault of course a quiz so water and salt Alright So the typical neutralization reaction is acid reacting with base producing water and salt. And we discussed in detail what happened during the process. Both of the two solutions in reactants, you have strong electrolytes fully dissociated into ions. Okay, these four, two positive, two negative, mobile ions. then meet in the solution and have a chance to try each other out. Okay. And obviously, in this case, your H plus ion, so you have HCl fully dissociate into hydrogen ion and chloride ion. Okay, and you have sodium hydroxide fully dissociated into sodium ion and hydroxide. Okay, so two positive, two negative, all in the same solution now. Positive ions are going to be attracted to negative ions, and hydrogen ions, even if it is attracted to chloride ion, or when they get together, they make HCl. HCl is a strong electrolyte. It's going to full dissociate into ions again. There's nothing going to happen between these two. Okay? They're not getting back together. Similarly, would there be anything happening to these two? No. They're not getting back together. Okay? But... Your hydrogen could be running into, attracted to, your hydroxide. And as you can see, when these two get together, they hit it off. You ended up getting water molecule. Now, this is a molecular compound that won't dissociate. Water molecules won't easily dissociate into hydrogen ions and hydroxide ions. Okay? Otherwise, it's not going to be safe for you to drink water. You're going to take some double corrosion on your stomach. And now, then, would these two get together? Well, they probably would be attracted to each other. But even if they get together, are you going to have little sodium chloride units in your solution? Sodium chloride is a soluble salt. Soluble salt dissociates 100%. Okay, so these two can hook up for a moment because of the electrostatic attraction, but they will separate their ways. Okay, so really, you're not going to have NaCl per se. You're going to have Na, and you're going to have Cl. All of these ions, of course, are going to be aqueous. Ions yeah, so with this we've got with this reaction. We have a chemical reaction equation that looks familiar with all the chemical compounds involved. There's HCl, there's NaOH, there's water, there's sodium chloride. Okay, and an equation like this, where you show all the compounds in their, either their molecular formula or their formula units for ionic compounds, we call this a molecular equation. A molecular equation gave you the chemicals involved in a given chemical reaction, okay? But if you're looking at our analysis for the entire process, if you understand our analysis on the process, you know that the molecular equation doesn't tell the whole story of the chemical reaction, okay? It looks like you have a molecular compound. You don't really have an HCl molecule, a single HCl molecule in this entire process. Okay? Looks like you ended up getting sodium chloride. Well, your sodium chloride is not, sodium and chloride is not staying together. So molecular equation gave you this chemical compounds that's involved in a chemical reaction. But in a solution chemical reaction, It doesn't tell the whole story. Well, what tells the whole story? What you have here tells the whole story. This sign here gave you every sign that actually existed in the solution. Reactants are really four different ions. Products is a molecule. and two free ions. These are the things that actually exist in the solution. Okay, and if we write them all out this should look like this. H plus plus Cl negative plus Na plus plus OH negative and then produce water molecule. Sodium ion and chloride ion. And this long form of the equation that shows every actual particle, be it a molecule or an ion, a free ion, in this entire solution process, this is what we call a full. Ionic equation, okay? so molecular equation Simply tell you what chemicals what compounds are involved in reaction full ionic equation Gave you the overall big picture of what's happening Inside your solution who's present what species? are present in your solution during the process of the reaction. And if you look at our full ionic equation, though, you realize that there are some things that's the same on the two sides. What do you mean? Well, look at this. There's free chloride ion. Yeah, on the left side of the equation. There's free chloride ion on the right side of the equation. And let's think about this process, okay? Did anything really happen to the chloride ion at all? They free up themselves from the strong acid HCl, okay? They got out the chloride ions. And they run around, they won't go back together with H+. They may run into sodium plus, but then realize, okay, they're not made for each other. So nothing really happened to the chloride ion. And similarly, did anything really happen to your sodium ion? Since the moment he got free from solid sodium hydroxide He becomes a free ion. Okay. He looks around. There's no negative ion that makes him want to settle down. He either make the two compounds he made is a strong base and a soluble salt. Both dissociate 100% anyway. Okay. So it is common. Not always, but it is common. That in your full ionic equation, you would have some of the same ions on both sides. Okay? And these ions... Now, remember, this thing is called a full ionic equation. What do we do in a mathematical equation if you have the same things on both sides? You cancel them, right? Well, you can do the exact same. with a full ionic equation, with a chemical equation. There's chloride ion on both sides. I can cancel them. There's sodium ion on both sides. I can cancel that. Now once you cancel these same things on both sides of your full ionic equation, what you got left is a much more simplified version of your chemical reaction. H plus ion reacting with hydroxide ion producing water molecule. That's it. Okay? This equation here, after we cancel the same things, This represents the real chemistry. What in, what's, full ionic equation gave you all the species, okay, everything that's present in your solution during the chemical reaction process. This equation here gave you what species among everything that you listed in the full ionic equation actually went through some kind of chemistry. and get you new stuff. Remember, chloride never changed, not new stuff. Sodium never changed, no new stuff. What's new? This water molecule that comes from the H plus and OH negative is new. It wasn't there before. There are some water molecules here in the solution, but this water molecule wasn't there. Before that, you have two nasty chemicals, an acid and a base, both corrosive. But once they got together, you got clean, neutral, non-corrosive water molecule. This equation here represents the real chemistry in this chemical neutralization reaction. And this is what we call... A equation like this where we cancelled all the same things from the full ionic equation. This is what we call the net ionic equation. And essentially, every solution chemical reaction that you're going to be dealing with in Chem 115 really have three different forms. The molecular equation. full ionic equation and the net ionic equation. Obviously, they're all related to each other. They're all representing the same chemical reaction, okay? But molecular equation have all the compound formulas, okay? You won't see a free ion in the molecular equation. Full ionic equation have every single species that's present, whether or not they had gone through any chemistry, okay? And The net ion equation represents the real chemistry of this entire process. Okay. And the ions that you canceled, in this case, the sodium and the chloride. Okay. Why are they canceled? Because they never changed. Okay. So they're not part, they're part of the reaction. They're present. Okay. But. They don't have real chemistry happen to them. And ions like this, we call them spectator ions. And why do we call them spectators? Because that's what they did. Okay? They didn't do anything there. They're... Now, if H plus and... OH negative, okay, are the two ions that are falling in love with each other. And this process of real chemistry of them turning into a water molecule is the wedding between these two ions. Then sodium and chloride, okay, are there, okay, as a witness. The wedding itself has nothing to do with them. The real chemistry doesn't exist for them. But they were there. They witnessed this whole process. Okay? They are the spectators. Alright? So, now, really, the real chemistry here, of course, is... the H plus and the OH negative. Now, here's the deal. I can give you another strong acid, let's say HNO3, okay, and another strong base, let's say calcium hydroxide. Okay, they look completely different, right? Now. And what kind of chemical reactions are going to happen to them when you put these two acid and base, this acid and this base together? Now, you can write the molecular equation without thinking about who breaks down. Which compound dissociate? Instead, molecular equation for neutralization reaction can be done very easily through some prediction work. What do you mean? Well, your calcium was with hydroxide right now. Okay. Now, if you're going to have a chemical reaction, and with an acid and a base, you're definitely going to have a chemical reaction. Okay. Now, what's the only possibility? for calcium to turn to. Your calcium is going to have to go after the nitrate, okay? It won't be together with hydroxide anymore, okay? And remember, this type of reaction is all about exchange partners, okay? So calcium is going to go with nitrate. Don't just put down CaNO3 yet, because you've got to realize that calcium is in group 2, so it's plus 2 charge. Nitrate is with hydrogen, with only one hydrogen in nitric acid, okay? Hydrogen is always plus one, and that makes your nitrate negative one, okay? So plus two and negative one, can they match up like this and give you neutral compound? They won't. You're going to need two of those, okay? And then... Yeah. How are you going to get two nitrate? Well, each one molecule gave you one nitrate. You better have two molecules of HNO3 to get two nitrates. Okay. And then, of course, your hydrogen is going to get together with your hydroxide and produce your water. We already know that. And you have two hydrogen and two hydroxide. So obviously, you're going to make two water molecules. So look, without... Going who's full who's dissociating into what ions you can still write molecular equation pretty easily Okay, and writing molecular equation is all about Exchange partner. Positive exchange negative, negative exchange positive, however you want to see it. However you want to say it. Okay, and forming form neutral compound. If you can... Do these two things. You can write your molecular equation for solution chemical reactions very easily. You can write your molecular equation for double displacement reactions very easily. Okay? Now, and then, of course, how do I go from there to full ionic equation? Well, easy. Look at your chemicals in your molecular equation. Determine what they are. This is a strong acid. This is a strong base. Now this, we haven't got there yet, but I'll tell you this is a soluble salt. Okay? So all three of them are strong electrolytes, and water, again, is a molecular compound. Okay, so strong electrolytes, full dissociation, 100%, which means there's only ions, there's no molecules, there's no formula units together, it's just ions. So you can dissociate into ions. 2H plus and 2 nitrate. And calcium, you have 2 plus calcium ions and 2 hydroxide ions. Calcium nitrate, soluble salt, so 1 calcium and 2 nitrate. And then water, or just water. See, by analyzing your molecular equation and labeling them as, you know, different kind of electrolytes, then you can decide, okay, if it's full. if it's strong electrolyte I'm going to have to dissociate them into ions if it's a molecular compound I can't what if it's a weak electrolyte we're going to get there we're going to talk about the rules for weak electrolyte And it's simple. For weak electrolytes, you keep them in the molecular form. You don't dissociate it to get your full ionic equation because your molecular form exists in the solution. For strong acid, the molecular form don't exist in the solution. It's just free ions. All right, so... You look at this, oh, okay, I have calcium ion, never changed. I have two nitrate ion, never changed. So these two are my spectator ions. And then what I got left, 2H+, 2OH-, 2 water. Okay, 2 to 2 ratio is 1, 1, 1 ratio. So cancel the spectator ion. And I ended up getting the net ionic equation. And when you get here, so this is full. Ionic, this is net ionic. And once you get here, you realize, oh, these two are essentially the same chemical reaction. Now, look at the molecular equation. Aside from water, three out of the four components of the reaction in the molecular equation are different. Okay? But once you break it down into real chemistry and real species that exists in solution, and you take away the different bystanders, the different spectators, they do have different spectator ions. In this equation, it's sodium and chloride. In this one, it's calcium and nitrate. But once you put these... Spectators away you realize the real chemistry between these two is the exact same. They're both Strong acid neutralizes strong base and turning into water. Okay, so Neutralization reactions are like this now what if you have a weak electrolyte a weak acid or We're gonna deal with that once we finish our Next part now This type of reaction, like we said, neutralization reaction, belongs to what we call the double displacement. reaction. Okay. Double displacement. Two ionic compounds, two electrolytes exchange their positive-negative partners and gave you two new combinations. All right. And neutralization is obviously a double displacement reaction. Here's another type of double displacement reaction that we call Thank you precipitation reaction. Okay? Now why is it called precipitation? Now this, you probably hear this word a lot in weather reports. Okay, whenever they tell you there's gonna be precipitation, they're essentially saying, okay, like something is gonna be coming down from the sky. Okay, whether it's rain or snow or hail, you know. Something's coming down. Precipitation means something coming down. How does that relate to a particular type of chemical reaction? A precipitation reaction describes a chemical reaction where you put two solutions together, and the reaction between the two compounds, two solids in your solution, makes this insoluble ionic compound. a solid that because the solid is having a higher density than your solution eventually now you see the solution get muddy and eventually the salt you see the salt going down to the bottom of your beaker your test tube your container okay that that process involved solid from all over the solution going down to the bottom and that's why it is called a precipitation reaction Okay, so here's the example of a precipitation reaction and since it's also a double displacement reaction We're going to try to view it the exact same way that we viewed our neutralization reaction earlier. Okay, so precipitation reaction is lead nitrate reacting with sodium sulfate producing precipitate and another product okay so first of all let's use the same way that we use dealing with the neutralization reaction now now we know if i know two come two electrolytes are mixed together i can actually predict the product pretty easily okay and i'm doing the exact same thing that i did earlier sodium is now with sulfate okay and This is made into a solution, so that means both of them are soluble, and soluble salts are strong electrolyte, 100% dissociation. That means your sodium is not going to be with sulfate anymore. So what is your sodium going to do? Your sodium is going to run into or being attracted to the only other negative ion. Sulfate is already done with it. The other negative ion, obviously, is the nitrate ion. Okay, so your Na is going to get together with nitrate. Okay, but before you decide anything, let's make sure that I got a correct formula. I need to know the charge. Sodium is in group one, so that's obviously a plus one charge for each sodium. Now nitrate, we just talked about it. Nitric acid is HNO3, 1H. One positive charge, that means nitride ion has one negative charge. Oh, okay, so these two can match up one-on-one. Good. NaNO3 is a valid chemical formula for a neutral compound. All right, and then we'll worry about the subscripts later. That's something that I'm actually going to emphasize on because I've seen numerous mistakes and persistent mistakes on that. But lead... It's not going to be together with nitrate anymore. Okay, it's a soluble salt. They're going to part their ways and never get back again. Okay, but lead is... So the only other thing that lead ion, metal positive ion, is going to be attracted to is the other negative ion, which is the sulfate ion. Okay, so lead and sulfate is going to get together. Okay, again, let's figure out the charge. Sodium is plus one. I have two sodium, and that charge is canceled by the sulfate, so sulfate must be negative two. And also, you can figure that out from the sulfuric acid. Formula, H2SO4, and each hydrogen is plus one, so SO4 got to be negative two. Okay? Now, and what about the charge on lead? Well, each nitrate is negative one. We established that, right? And this is a neutral ionic compound, so you have two nitrate. That's a total of negative two, and lead make the whole thing neutral, no doubt. Lead is plus two. Oh, plus two and negative two. This is perfect one-to-one ratio as well. Okay, now and now you predict the second product Okay, and of course you can now you now let's look at the subscript Right now this equation is not balanced because you have two sodium here two nitrate here And you only have one sodium and one nitrate on this and but since you have two of those very easy for you to put the two there and Now you have two of each. Yeah, and Time and time again, I observed this. Oh, Na2, Na2, Na3, 2. This is going to be counted wrong every single time in every level of chemistry class. Why? Didn't that also cancel the charge, plus 2 and negative 2? Well... Ionic compounds, okay, because they don't have any molecules, okay, you have to have the smallest whole number ratio for ions, okay? 2 to 2 is not the smallest whole number ratio. One to one is. That's why. All right. But as you can see, just by comparing what compounds we have, what kind of charge and by exchange partner and match up charge. Okay. We predicted the two products and we got. the molecular formula now a molecular equation now it's kind of funny that when you have four ionic compounds in this equation you still call it a molecular equation but with compound formula all compound formula in the equation no individual ions people are going to call it molecular equation that's just through okay a hundred years of accumulation And we formed habit to do that, and we're not about to change that. All right, so molecular equation is done here. And of course, to look for the real chemistry, I'm going to have to do the full ionic equation. And then, of course, the net ionic equation. Let's see. We already said these are two soluble salts. Soluble salts dissociate 100%. I can do this pretty easily. Lead nitrate should be lead ion and two nitrate ion. Okay, don't do this. The reason of that is simple. Okay. When you have apprentices have and the two there, that means those two ions are bonded together. Okay. You're saying that there are two NO3 units bonded together and show a negative two charge to the outside. That's not the case. Each NO3 is a. polyatomic negative ion, okay, that carries a negative one charge on the group of four atoms. The two of them have no reason to stick together. You're going to end up with two free nitrate ions trying to stay away from each other. This means you're making them sticking together. They're not. All right, so soluble salt dissociated 100%. Put it into ions. Sodium sulfate, I'm going to tell you, it's also soluble. And, well, it's already aqueous. You made a solution. Of course it's soluble. Two sodium ions and one sulfate ion. Again, don't you ever do this. Writing the Na ion like this shows that you don't have a good understanding of solution chemistry, of ion chemistry. Okay, each sodium ion is carrying a positive one charge. What makes you think that two sodium ions would actually stick together? Putting the two here in the subscript means you're saying these two ions actually stick together. as a unit, okay? These two sodium ions, Na plus ions, have no reason whatsoever to be attracted to each other. They have the same charge, for Christ's sake, okay? The only thing they want to do after they're freed up from that solid three-dimensional array structure, okay, the only thing they want to do to each other is to push each other away. You have positive charge, you have positive charge, stay away from me. Okay? So, now, these are the things on the left side. Now, on the right side, for your products, okay? You don't know it yet, and we will talk about it later. I'm going to tell you that sodium nitrate is also a soluble salt. You're also going to have an aqueous form of it that dissociates into ions. And, of course, when this dissociates, each one of them is dissociating into Na+, and nitrate negative. And of course, you're going to end up with two of each because you have two there. Now, anyway, so NaNO3 is soluble. Now, here comes our final product, final component of the equation, lead sulfate. Okay. And also, I'm going to tell you, you can't judge it as of right now. I haven't given you enough information, but I'm going to give you that judgment. Lead sulfate is an insoluble ionic compound. Insoluble means what? It means you can put that solid into water. It's not going to disappear like table salt will. It's going to remain the solid form. Now, since we didn't really add this solid into water, we put these two solutions together, and they ended up making me this. Okay, so how should I represent this? This would be the insoluble ionic compound that you made would be your precipitation. Okay, now imagine that you have this beaker. Okay, you have some... free ions you have sodium ions you have lead ions you have nitrate ions and you have sulfate ions you probably have another sodium ion here And then another. Nitrate ion here somewhere. Okay, you have all these free ions. And these two are going to run into each other. And once they run into each other, they found, just like H plus and OH negative, oh, this is my soulmate. I want to stay together with this ion. I want to stay together with this guy. Okay? And we want to stay together. I don't want to move around by myself in this solution. So what's gonna happen? They become a solid. Okay? This is where you say that precipitation, you see the solution becomes two clear solutions. In this case, mixing together and all of a sudden the solution becomes muddy, okay? Milky color. And then, inside your beaker, you're still going to have your sodiums, your nitrates. Your nitrates, your sodiums. Nothing is going to happen to those guys. They run into each other, but it didn't work out. Okay? But now, after everything is set... settle down you would have some solid staying at the bottom of your beaker okay this would be the precipitate of lead sulfate okay and We're going to put an S there to represent the physical state of this particular compound in solution. It's insoluble, so lead sulfate is going to remain a solid. It's not going to have an aqueous form. Now, if it doesn't even dissolve, can you dissociate it into ions? Of course you can't, because that's not what happened. Now, what's going to happen here? This is your full ionic equation of this precipitation reaction. So we went from molecular equation to a full ionic equation. And then you realize, oh, this one has spectator ions as well. Remember sodium? Look at nitrate. They are the same on both sides of the equation, and we can cancel them as spectator. Spectator ions are sodium ions and nitrate ions. Now, once you cancel them, what you got left? Lead. Sofit, let's sofit solid. This will be your net ionic equation. Okay? Now... The entire process have involved different chemicals and it's not acid base anymore, but you can still see that precipitation reaction really is the same kind with your neutralization reaction. What happened is the exact same kind of process. It's not the exact same things, but it's the exact same kind of process. Two electrolytes exchange partner, making something that can easily dissociate. For neutralization, it's making water. which is a molecular compound that you can't dissociate. For precipitation, you're making a solid insoluble ionic compound that won't dissociate, okay? And then you can predict products of your molecular equation. You can, by learning whether they're soluble, insoluble, break things down into your full ionic equation. And then, of course, you can cancel your spectator ions and get your... nanionic equation okay now so of course now this then comes down to another issue yeah when you write this equation predict the product and doing the full ionic equation you had to tell me this is soluble this is soluble this is soluble this is insoluble Then I can do what I did. Can you give me what's soluble, what's insoluble every single time on every question that we're going to have? Well, of course, you know I won't, okay? Do you expect me to know every... electrolyte that's out there who's soluble, who's insoluble to determine a precipitation reaction? No, I don't expect you to remember every single ionic compounds out there. There are thousands of them, okay? So what am I supposed to do? Because without knowing this soluble, insoluble information, I can't make a judgment. I can't turn it into a full ionic equation and then net ionic equation. Well, I'm going to give you a set of rules, okay? And using this set of rules, you're going to be able to judge every ionic compound or electrolyte, every ionic compound you're going to be running into in this class, who's soluble and who's insoluble. And that's what we call the set of. Previously, whenever we have these sodium compounds, sodium hydroxide, sodium chloride on the neutralization reaction, sodium sulfate, sodium nitrate here on that equation, this explains why. Solubility rules. With the solubility rules. you're going to be able to determine who's soluble and who's insoluble. So we're going to write them down for this class at the end of this class and we're going to have a detailed discussion of it on our next video lecture. Solubility rule number one, ionic compounds containing Group 1 metal cations or ammonium cations are always soluble. Okay, what does that mean? Group 1A metal cations, what are they? Lycium, sodium, potassium, rubidium, and cesium. Every single one of them have plus one charge because it's group 1A. Okay, alkali metals always make plus one charge positive ions. And... Ammonium ion. These six ions are your always soluble positive ions. And this explains to you why All of these are soluble because they all contain sodium. So if you look at a chemical formula and you look on the left side on the metal cation side, okay, you see any of these six positive ions right there. Don't even bother with the negative ion, right? soluble and that means whatever compound that you're looking at absolutely break it down into free moving ions and number two here We're gonna give you a rule that is very similar Even in wording ionic compound containing Nitrate ion, nitrite ion, chlorate ion, perchlorate ion, acetate ion, and bicarbonate ion. are always soluble Rule number one, you have six positive ions. Whenever you see these guys in compound, no matter what negative ions you have, they're always soluble. Rule number two is kind of the equivalent, okay, but this time you have, what, six negative, six cations, that's always soluble. Rule number two gives you six anions. Okay, that's always soluble. You see these guys in your chemical formula of the ionic compound? I don't care what weird metal is up front. Okay. Copper nitrate, soluble. Okay, titanium chlorate, soluble. Okay, silver acetate, soluble. That's the acetate. Okay. Doesn't matter. Gold, bicarbonate, soluble. Okay? And soluble means what? Soluble ionic compound means what? Dissociate 100%. So these are the first two rules of the solubility rules. These are 12 always soluble ions. Six positive, six negative. We'll pick up from here on next Monday's lecture.

Chem 115 for 2020 lecture on September 25th. Okay, so on Wednesday's lecture, we discussed, we stopped at the neutralization reaction. A typical solution chemical reaction.

And the reaction that we used as the example is the reaction between hydrochloric acid solution and sodium hydroxide liquid solution, strong acid. Strong base Reacting with each other and their product of that is acid and base neutralize each other produce water liquid and Assault of course a quiz so water and salt Alright So the typical neutralization reaction is acid reacting with base producing water and salt. And we discussed in detail what happened during the process. Both of the two solutions in reactants, you have strong electrolytes fully dissociated into ions. Okay, these four, two positive, two negative, mobile ions.

then meet in the solution and have a chance to try each other out. Okay. And obviously, in this case, your H plus ion, so you have HCl fully dissociate into hydrogen ion and chloride ion.

Okay, and you have sodium hydroxide fully dissociated into sodium ion and hydroxide. Okay, so two positive, two negative, all in the same solution now. Positive ions are going to be attracted to negative ions, and hydrogen ions, even if it is attracted to chloride ion, or when they get together, they make HCl.

HCl is a strong electrolyte. It's going to full dissociate into ions again. There's nothing going to happen between these two.

Okay? They're not getting back together. Similarly, would there be anything happening to these two?

No. They're not getting back together. Okay? But...

Your hydrogen could be running into, attracted to, your hydroxide. And as you can see, when these two get together, they hit it off. You ended up getting water molecule. Now, this is a molecular compound that won't dissociate.

Water molecules won't easily dissociate into hydrogen ions and hydroxide ions. Okay? Otherwise, it's not going to be safe for you to drink water.

You're going to take some double corrosion on your stomach. And now, then, would these two get together? Well, they probably would be attracted to each other. But even if they get together, are you going to have little sodium chloride units in your solution?

Sodium chloride is a soluble salt. Soluble salt dissociates 100%. Okay, so these two can hook up for a moment because of the electrostatic attraction, but they will separate their ways.

Okay, so really, you're not going to have NaCl per se. You're going to have Na, and you're going to have Cl. All of these ions, of course, are going to be aqueous.

Ions yeah, so with this we've got with this reaction. We have a chemical reaction equation that looks familiar with all the chemical compounds involved. There's HCl, there's NaOH, there's water, there's sodium chloride.

Okay, and an equation like this, where you show all the compounds in their, either their molecular formula or their formula units for ionic compounds, we call this a molecular equation. A molecular equation gave you the chemicals involved in a given chemical reaction, okay? But if you're looking at our analysis for the entire process, if you understand our analysis on the process, you know that the molecular equation doesn't tell the whole story of the chemical reaction, okay?

It looks like you have a molecular compound. You don't really have an HCl molecule, a single HCl molecule in this entire process. Okay? Looks like you ended up getting sodium chloride.

Well, your sodium chloride is not, sodium and chloride is not staying together. So molecular equation gave you this chemical compounds that's involved in a chemical reaction. But in a solution chemical reaction, It doesn't tell the whole story. Well, what tells the whole story?

What you have here tells the whole story. This sign here gave you every sign that actually existed in the solution. Reactants are really four different ions.

Products is a molecule. and two free ions. These are the things that actually exist in the solution. Okay, and if we write them all out this should look like this.

H plus plus Cl negative plus Na plus plus OH negative and then produce water molecule. Sodium ion and chloride ion. And this long form of the equation that shows every actual particle, be it a molecule or an ion, a free ion, in this entire solution process, this is what we call a full. Ionic equation, okay?

so molecular equation Simply tell you what chemicals what compounds are involved in reaction full ionic equation Gave you the overall big picture of what's happening Inside your solution who's present what species? are present in your solution during the process of the reaction. And if you look at our full ionic equation, though, you realize that there are some things that's the same on the two sides. What do you mean?

Well, look at this. There's free chloride ion. Yeah, on the left side of the equation. There's free chloride ion on the right side of the equation.

And let's think about this process, okay? Did anything really happen to the chloride ion at all? They free up themselves from the strong acid HCl, okay?

They got out the chloride ions. And they run around, they won't go back together with H+. They may run into sodium plus, but then realize, okay, they're not made for each other.

So nothing really happened to the chloride ion. And similarly, did anything really happen to your sodium ion? Since the moment he got free from solid sodium hydroxide He becomes a free ion.

Okay. He looks around. There's no negative ion that makes him want to settle down. He either make the two compounds he made is a strong base and a soluble salt.

Both dissociate 100% anyway. Okay. So it is common.

Not always, but it is common. That in your full ionic equation, you would have some of the same ions on both sides. Okay? And these ions... Now, remember, this thing is called a full ionic equation.

What do we do in a mathematical equation if you have the same things on both sides? You cancel them, right? Well, you can do the exact same. with a full ionic equation, with a chemical equation. There's chloride ion on both sides.

I can cancel them. There's sodium ion on both sides. I can cancel that. Now once you cancel these same things on both sides of your full ionic equation, what you got left is a much more simplified version of your chemical reaction.

H plus ion reacting with hydroxide ion producing water molecule. That's it. Okay?

This equation here, after we cancel the same things, This represents the real chemistry. What in, what's, full ionic equation gave you all the species, okay, everything that's present in your solution during the chemical reaction process. This equation here gave you what species among everything that you listed in the full ionic equation actually went through some kind of chemistry.

and get you new stuff. Remember, chloride never changed, not new stuff. Sodium never changed, no new stuff.

What's new? This water molecule that comes from the H plus and OH negative is new. It wasn't there before. There are some water molecules here in the solution, but this water molecule wasn't there. Before that, you have two nasty chemicals, an acid and a base, both corrosive.

But once they got together, you got clean, neutral, non-corrosive water molecule. This equation here represents the real chemistry in this chemical neutralization reaction. And this is what we call... A equation like this where we cancelled all the same things from the full ionic equation.

This is what we call the net ionic equation. And essentially, every solution chemical reaction that you're going to be dealing with in Chem 115 really have three different forms. The molecular equation.

full ionic equation and the net ionic equation. Obviously, they're all related to each other. They're all representing the same chemical reaction, okay? But molecular equation have all the compound formulas, okay?

You won't see a free ion in the molecular equation. Full ionic equation have every single species that's present, whether or not they had gone through any chemistry, okay? And The net ion equation represents the real chemistry of this entire process.

Okay. And the ions that you canceled, in this case, the sodium and the chloride. Okay. Why are they canceled? Because they never changed.

Okay. So they're not part, they're part of the reaction. They're present.

Okay. But. They don't have real chemistry happen to them.

And ions like this, we call them spectator ions. And why do we call them spectators? Because that's what they did.

Okay? They didn't do anything there. They're...

Now, if H plus and... OH negative, okay, are the two ions that are falling in love with each other. And this process of real chemistry of them turning into a water molecule is the wedding between these two ions.

Then sodium and chloride, okay, are there, okay, as a witness. The wedding itself has nothing to do with them. The real chemistry doesn't exist for them. But they were there.

They witnessed this whole process. Okay? They are the spectators.

Alright? So, now, really, the real chemistry here, of course, is... the H plus and the OH negative. Now, here's the deal.

I can give you another strong acid, let's say HNO3, okay, and another strong base, let's say calcium hydroxide. Okay, they look completely different, right? Now. And what kind of chemical reactions are going to happen to them when you put these two acid and base, this acid and this base together? Now, you can write the molecular equation without thinking about who breaks down.

Which compound dissociate? Instead, molecular equation for neutralization reaction can be done very easily through some prediction work. What do you mean? Well, your calcium was with hydroxide right now. Okay.

Now, if you're going to have a chemical reaction, and with an acid and a base, you're definitely going to have a chemical reaction. Okay. Now, what's the only possibility? for calcium to turn to. Your calcium is going to have to go after the nitrate, okay?

It won't be together with hydroxide anymore, okay? And remember, this type of reaction is all about exchange partners, okay? So calcium is going to go with nitrate.

Don't just put down CaNO3 yet, because you've got to realize that calcium is in group 2, so it's plus 2 charge. Nitrate is with hydrogen, with only one hydrogen in nitric acid, okay? Hydrogen is always plus one, and that makes your nitrate negative one, okay?

So plus two and negative one, can they match up like this and give you neutral compound? They won't. You're going to need two of those, okay? And then...

Yeah. How are you going to get two nitrate? Well, each one molecule gave you one nitrate. You better have two molecules of HNO3 to get two nitrates. Okay.

And then, of course, your hydrogen is going to get together with your hydroxide and produce your water. We already know that. And you have two hydrogen and two hydroxide. So obviously, you're going to make two water molecules.

So look, without... Going who's full who's dissociating into what ions you can still write molecular equation pretty easily Okay, and writing molecular equation is all about Exchange partner. Positive exchange negative, negative exchange positive, however you want to see it. However you want to say it.

Okay, and forming form neutral compound. If you can... Do these two things.

You can write your molecular equation for solution chemical reactions very easily. You can write your molecular equation for double displacement reactions very easily. Okay? Now, and then, of course, how do I go from there to full ionic equation?

Well, easy. Look at your chemicals in your molecular equation. Determine what they are.

This is a strong acid. This is a strong base. Now this, we haven't got there yet, but I'll tell you this is a soluble salt. Okay?

So all three of them are strong electrolytes, and water, again, is a molecular compound. Okay, so strong electrolytes, full dissociation, 100%, which means there's only ions, there's no molecules, there's no formula units together, it's just ions. So you can dissociate into ions.

2H plus and 2 nitrate. And calcium, you have 2 plus calcium ions and 2 hydroxide ions. Calcium nitrate, soluble salt, so 1 calcium and 2 nitrate.

And then water, or just water. See, by analyzing your molecular equation and labeling them as, you know, different kind of electrolytes, then you can decide, okay, if it's full. if it's strong electrolyte I'm going to have to dissociate them into ions if it's a molecular compound I can't what if it's a weak electrolyte we're going to get there we're going to talk about the rules for weak electrolyte And it's simple.

For weak electrolytes, you keep them in the molecular form. You don't dissociate it to get your full ionic equation because your molecular form exists in the solution. For strong acid, the molecular form don't exist in the solution.

It's just free ions. All right, so... You look at this, oh, okay, I have calcium ion, never changed.

I have two nitrate ion, never changed. So these two are my spectator ions. And then what I got left, 2H+, 2OH-, 2 water.

Okay, 2 to 2 ratio is 1, 1, 1 ratio. So cancel the spectator ion. And I ended up getting the net ionic equation. And when you get here, so this is full. Ionic, this is net ionic.

And once you get here, you realize, oh, these two are essentially the same chemical reaction. Now, look at the molecular equation. Aside from water, three out of the four components of the reaction in the molecular equation are different. Okay? But once you break it down into real chemistry and real species that exists in solution, and you take away the different bystanders, the different spectators, they do have different spectator ions.

In this equation, it's sodium and chloride. In this one, it's calcium and nitrate. But once you put these... Spectators away you realize the real chemistry between these two is the exact same. They're both Strong acid neutralizes strong base and turning into water.

Okay, so Neutralization reactions are like this now what if you have a weak electrolyte a weak acid or We're gonna deal with that once we finish our Next part now This type of reaction, like we said, neutralization reaction, belongs to what we call the double displacement. reaction. Okay. Double displacement.

Two ionic compounds, two electrolytes exchange their positive-negative partners and gave you two new combinations. All right. And neutralization is obviously a double displacement reaction.

Here's another type of double displacement reaction that we call Thank you precipitation reaction. Okay? Now why is it called precipitation? Now this, you probably hear this word a lot in weather reports. Okay, whenever they tell you there's gonna be precipitation, they're essentially saying, okay, like something is gonna be coming down from the sky.

Okay, whether it's rain or snow or hail, you know. Something's coming down. Precipitation means something coming down.

How does that relate to a particular type of chemical reaction? A precipitation reaction describes a chemical reaction where you put two solutions together, and the reaction between the two compounds, two solids in your solution, makes this insoluble ionic compound. a solid that because the solid is having a higher density than your solution eventually now you see the solution get muddy and eventually the salt you see the salt going down to the bottom of your beaker your test tube your container okay that that process involved solid from all over the solution going down to the bottom and that's why it is called a precipitation reaction Okay, so here's the example of a precipitation reaction and since it's also a double displacement reaction We're going to try to view it the exact same way that we viewed our neutralization reaction earlier.

Okay, so precipitation reaction is lead nitrate reacting with sodium sulfate producing precipitate and another product okay so first of all let's use the same way that we use dealing with the neutralization reaction now now we know if i know two come two electrolytes are mixed together i can actually predict the product pretty easily okay and i'm doing the exact same thing that i did earlier sodium is now with sulfate okay and This is made into a solution, so that means both of them are soluble, and soluble salts are strong electrolyte, 100% dissociation. That means your sodium is not going to be with sulfate anymore. So what is your sodium going to do? Your sodium is going to run into or being attracted to the only other negative ion.

Sulfate is already done with it. The other negative ion, obviously, is the nitrate ion. Okay, so your Na is going to get together with nitrate.

Okay, but before you decide anything, let's make sure that I got a correct formula. I need to know the charge. Sodium is in group one, so that's obviously a plus one charge for each sodium. Now nitrate, we just talked about it.

Nitric acid is HNO3, 1H. One positive charge, that means nitride ion has one negative charge. Oh, okay, so these two can match up one-on-one. Good.

NaNO3 is a valid chemical formula for a neutral compound. All right, and then we'll worry about the subscripts later. That's something that I'm actually going to emphasize on because I've seen numerous mistakes and persistent mistakes on that. But lead...

It's not going to be together with nitrate anymore. Okay, it's a soluble salt. They're going to part their ways and never get back again.

Okay, but lead is... So the only other thing that lead ion, metal positive ion, is going to be attracted to is the other negative ion, which is the sulfate ion. Okay, so lead and sulfate is going to get together. Okay, again, let's figure out the charge. Sodium is plus one.

I have two sodium, and that charge is canceled by the sulfate, so sulfate must be negative two. And also, you can figure that out from the sulfuric acid. Formula, H2SO4, and each hydrogen is plus one, so SO4 got to be negative two.

Okay? Now, and what about the charge on lead? Well, each nitrate is negative one. We established that, right? And this is a neutral ionic compound, so you have two nitrate.

That's a total of negative two, and lead make the whole thing neutral, no doubt. Lead is plus two. Oh, plus two and negative two. This is perfect one-to-one ratio as well.

Okay, now and now you predict the second product Okay, and of course you can now you now let's look at the subscript Right now this equation is not balanced because you have two sodium here two nitrate here And you only have one sodium and one nitrate on this and but since you have two of those very easy for you to put the two there and Now you have two of each. Yeah, and Time and time again, I observed this. Oh, Na2, Na2, Na3, 2. This is going to be counted wrong every single time in every level of chemistry class. Why?

Didn't that also cancel the charge, plus 2 and negative 2? Well... Ionic compounds, okay, because they don't have any molecules, okay, you have to have the smallest whole number ratio for ions, okay?

2 to 2 is not the smallest whole number ratio. One to one is. That's why.

All right. But as you can see, just by comparing what compounds we have, what kind of charge and by exchange partner and match up charge. Okay.

We predicted the two products and we got. the molecular formula now a molecular equation now it's kind of funny that when you have four ionic compounds in this equation you still call it a molecular equation but with compound formula all compound formula in the equation no individual ions people are going to call it molecular equation that's just through okay a hundred years of accumulation And we formed habit to do that, and we're not about to change that. All right, so molecular equation is done here. And of course, to look for the real chemistry, I'm going to have to do the full ionic equation.

And then, of course, the net ionic equation. Let's see. We already said these are two soluble salts. Soluble salts dissociate 100%.

I can do this pretty easily. Lead nitrate should be lead ion and two nitrate ion. Okay, don't do this.

The reason of that is simple. Okay. When you have apprentices have and the two there, that means those two ions are bonded together. Okay.

You're saying that there are two NO3 units bonded together and show a negative two charge to the outside. That's not the case. Each NO3 is a.

polyatomic negative ion, okay, that carries a negative one charge on the group of four atoms. The two of them have no reason to stick together. You're going to end up with two free nitrate ions trying to stay away from each other.

This means you're making them sticking together. They're not. All right, so soluble salt dissociated 100%.

Put it into ions. Sodium sulfate, I'm going to tell you, it's also soluble. And, well, it's already aqueous. You made a solution.

Of course it's soluble. Two sodium ions and one sulfate ion. Again, don't you ever do this. Writing the Na ion like this shows that you don't have a good understanding of solution chemistry, of ion chemistry.

Okay, each sodium ion is carrying a positive one charge. What makes you think that two sodium ions would actually stick together? Putting the two here in the subscript means you're saying these two ions actually stick together. as a unit, okay?

These two sodium ions, Na plus ions, have no reason whatsoever to be attracted to each other. They have the same charge, for Christ's sake, okay? The only thing they want to do after they're freed up from that solid three-dimensional array structure, okay, the only thing they want to do to each other is to push each other away. You have positive charge, you have positive charge, stay away from me.

Okay? So, now, these are the things on the left side. Now, on the right side, for your products, okay?

You don't know it yet, and we will talk about it later. I'm going to tell you that sodium nitrate is also a soluble salt. You're also going to have an aqueous form of it that dissociates into ions. And, of course, when this dissociates, each one of them is dissociating into Na+, and nitrate negative. And of course, you're going to end up with two of each because you have two there.

Now, anyway, so NaNO3 is soluble. Now, here comes our final product, final component of the equation, lead sulfate. Okay. And also, I'm going to tell you, you can't judge it as of right now. I haven't given you enough information, but I'm going to give you that judgment.

Lead sulfate is an insoluble ionic compound. Insoluble means what? It means you can put that solid into water.

It's not going to disappear like table salt will. It's going to remain the solid form. Now, since we didn't really add this solid into water, we put these two solutions together, and they ended up making me this.

Okay, so how should I represent this? This would be the insoluble ionic compound that you made would be your precipitation. Okay, now imagine that you have this beaker. Okay, you have some... free ions you have sodium ions you have lead ions you have nitrate ions and you have sulfate ions you probably have another sodium ion here And then another.

Nitrate ion here somewhere. Okay, you have all these free ions. And these two are going to run into each other. And once they run into each other, they found, just like H plus and OH negative, oh, this is my soulmate. I want to stay together with this ion.

I want to stay together with this guy. Okay? And we want to stay together. I don't want to move around by myself in this solution.

So what's gonna happen? They become a solid. Okay?

This is where you say that precipitation, you see the solution becomes two clear solutions. In this case, mixing together and all of a sudden the solution becomes muddy, okay? Milky color. And then, inside your beaker, you're still going to have your sodiums, your nitrates. Your nitrates, your sodiums.

Nothing is going to happen to those guys. They run into each other, but it didn't work out. Okay? But now, after everything is set...

settle down you would have some solid staying at the bottom of your beaker okay this would be the precipitate of lead sulfate okay and We're going to put an S there to represent the physical state of this particular compound in solution. It's insoluble, so lead sulfate is going to remain a solid. It's not going to have an aqueous form.

Now, if it doesn't even dissolve, can you dissociate it into ions? Of course you can't, because that's not what happened. Now, what's going to happen here? This is your full ionic equation of this precipitation reaction. So we went from molecular equation to a full ionic equation.

And then you realize, oh, this one has spectator ions as well. Remember sodium? Look at nitrate. They are the same on both sides of the equation, and we can cancel them as spectator. Spectator ions are sodium ions and nitrate ions.

Now, once you cancel them, what you got left? Lead. Sofit, let's sofit solid. This will be your net ionic equation.

Okay? Now... The entire process have involved different chemicals and it's not acid base anymore, but you can still see that precipitation reaction really is the same kind with your neutralization reaction.

What happened is the exact same kind of process. It's not the exact same things, but it's the exact same kind of process. Two electrolytes exchange partner, making something that can easily dissociate. For neutralization, it's making water.

which is a molecular compound that you can't dissociate. For precipitation, you're making a solid insoluble ionic compound that won't dissociate, okay? And then you can predict products of your molecular equation.

You can, by learning whether they're soluble, insoluble, break things down into your full ionic equation. And then, of course, you can cancel your spectator ions and get your... nanionic equation okay now so of course now this then comes down to another issue yeah when you write this equation predict the product and doing the full ionic equation you had to tell me this is soluble this is soluble this is soluble this is insoluble Then I can do what I did. Can you give me what's soluble, what's insoluble every single time on every question that we're going to have?

Well, of course, you know I won't, okay? Do you expect me to know every... electrolyte that's out there who's soluble, who's insoluble to determine a precipitation reaction? No, I don't expect you to remember every single ionic compounds out there.

There are thousands of them, okay? So what am I supposed to do? Because without knowing this soluble, insoluble information, I can't make a judgment.

I can't turn it into a full ionic equation and then net ionic equation. Well, I'm going to give you a set of rules, okay? And using this set of rules, you're going to be able to judge every ionic compound or electrolyte, every ionic compound you're going to be running into in this class, who's soluble and who's insoluble.

And that's what we call the set of. Previously, whenever we have these sodium compounds, sodium hydroxide, sodium chloride on the neutralization reaction, sodium sulfate, sodium nitrate here on that equation, this explains why. Solubility rules. With the solubility rules.

you're going to be able to determine who's soluble and who's insoluble. So we're going to write them down for this class at the end of this class and we're going to have a detailed discussion of it on our next video lecture. Solubility rule number one, ionic compounds containing Group 1 metal cations or ammonium cations are always soluble.

Okay, what does that mean? Group 1A metal cations, what are they? Lycium, sodium, potassium, rubidium, and cesium. Every single one of them have plus one charge because it's group 1A. Okay, alkali metals always make plus one charge positive ions.

And... Ammonium ion. These six ions are your always soluble positive ions.

And this explains to you why All of these are soluble because they all contain sodium. So if you look at a chemical formula and you look on the left side on the metal cation side, okay, you see any of these six positive ions right there. Don't even bother with the negative ion, right? soluble and that means whatever compound that you're looking at absolutely break it down into free moving ions and number two here We're gonna give you a rule that is very similar Even in wording ionic compound containing Nitrate ion, nitrite ion, chlorate ion, perchlorate ion, acetate ion, and bicarbonate ion. are always soluble Rule number one, you have six positive ions.

Whenever you see these guys in compound, no matter what negative ions you have, they're always soluble. Rule number two is kind of the equivalent, okay, but this time you have, what, six negative, six cations, that's always soluble. Rule number two gives you six anions.

Okay, that's always soluble. You see these guys in your chemical formula of the ionic compound? I don't care what weird metal is up front. Okay.

Copper nitrate, soluble. Okay, titanium chlorate, soluble. Okay, silver acetate, soluble. That's the acetate. Okay.

Doesn't matter. Gold, bicarbonate, soluble. Okay?

And soluble means what? Soluble ionic compound means what? Dissociate 100%. So these are the first two rules of the solubility rules. These are 12 always soluble ions.

Six positive, six negative. We'll pick up from here on next Monday's lecture.

Transcript for:Understanding Neutralization and Reactions

Transcript for:
Understanding Neutralization and Reactions