Chemistry 12 | Mr. Hogr | Chapter Six | Common lon | Lesson #48

Added: 2026-05-13

[00:00:12]This is a common guest in Wizardy.

[00:00:15]Common common guest.

[00:00:42]Uh buffer solution. You'll get that one also.

[00:00:46]Okay, I promise.

[00:00:49]What is the common ion?

[00:00:51]First of all, common ion common ion effect.

[00:00:58]It's better if I say common ion effect.

[00:01:02]How to get the common ion effect? It means we have two solutions.

[00:01:07]Solution of A and solution of B.

[00:01:20]Common ion.

[00:01:25]Okay, common ion. Common ion effect.

[00:01:34]What is the key point? The most important point. Common ion effect favors favors uh-huh the reverse reverse reaction.

[00:02:00]Direction.

[00:02:04]Always.

[00:02:13]Always we have reversed direction.

[00:02:18]According to Le Chatelier principle. So, common ion is a sequence or is a consequence or is a result of the Le Chatelier principle.

[00:02:29]But for solution is also common ion in this part in this topic we have we will have two solutions. Look, solution of A plus solution of B.

[00:02:47]Okay?

[00:02:49]We will have an ion in common between them. It means this solution it has its ions and this one it has its ions, okay?

[00:02:59]The ions here including cation and anion. Here we will have the ions.

[00:03:05]We will have the ions including a cation and anion.

[00:03:12]Okay?

[00:03:13]So, between these two solutions one of them must be in common. Common.

[00:03:20]One ion must be the same. Same ion.

[00:03:24]Example.

[00:03:27]This one has Cl, this one also has Cl ions. So, Cl will be in common. This is called common. And it will favor what direction? Reverse direction always.

[00:03:38]Either solution A will be reversed or this one will be reversed. Let's see.

[00:03:43]Yallah, common ion.

[00:03:45]Look.

[00:03:49]Common ion. In the common ion we will have two substances.

[00:03:54]Two substances, always.

[00:03:59]So, how many How many substances are there for the common ion? Of course, two substances. Be careful.

[00:04:05]We will have two substances. One of them, which is a salt salt plus weak acid or weak base.

[00:04:20]Look.

[00:04:21]One, two substances.

[00:04:23]>> [snorts] >> One, two substances, okay? So, we will have either these two together or either these two together.

[00:04:32]Okay? Or salt plus strong acid or strong base.

[00:04:46]I got a little bit wrong. Just write down this page and I'll be thankful.

[00:04:59]One, two substances or one, two substances, okay? One of them must be reversed always. Look at this.

[00:05:09]Mhm.

[00:05:11]If the acid or if the base is weak, then the acid will be reversed or the base will be reversed.

[00:05:21]So, we have weak acid or weak base, which one will be reversed? Salt or acid or base? Of course, the weak one will be reversed. So, in this case, we will say ionization ionization is decreased, okay? Uh-huh, like a lamba. Concentration of the weak is increased, okay?

[00:05:44]If the acid is reversed, H3O is decreased.

[00:05:49]If the base is reversed, OH is decreased.

[00:05:54]Okay?

[00:05:56]And then here, pH is increased. Here, pH is decreased. That's all.

[00:06:06]Salt plus weak, which one will be reversed?

[00:06:09]The weak one will be reversed.

[00:06:13]First of all, in the salt hydrolysis hydrolysis the last time, we have dissolved one salt in water. It means we have used one substance. But here, we will have two substances.

[00:06:25]The weak one will be reversed.

[00:06:27]Ionization is decreased, concentration of the weak is increased. If the weak one is the acid, H3O is decreased, pH is increased. If the weak one is the base, OH is decreased, pH is decreased.

[00:06:39]Come on. And if we have a strong acid or strong base along with the salt, in this case, the salt will be reversed.

[00:06:48]Dissociation Dissociation will be decreased, precipitation will be increased.

[00:07:00]Done.

[00:07:01]But there must be a common ion between them. That's all.

[00:07:07]I got weak one hour weak occur reversed that be. I got strong one hour weak occur reversed that be.

[00:07:12]Dissociation is decreased, precipitation is increased, amount of the salt Amount of the salt is increased, but concentration is unchanged.

[00:07:28]Cuz this is a solid one.

[00:07:30]So solid, the concentration for the solid one is unchanged.

[00:07:34]That's all.

[00:07:36]Come on.

[00:07:41]Bash.

[00:07:44]I have done that.

[00:07:45]>> Common ion occurs when an ion that is already contained in a solution, it means we have a solution that has an ion.

[00:07:55]An ion, okay? Not an ion, an ion.

[00:08:00]Okay, the same ion I have Zana.

[00:08:03]The same ion will be added to the solution. Same ion will be added.

[00:08:09]Generally, common ion promotes two things.

[00:08:13]I mean I mean common ion effect it will be not two things. Well, look. The common ion effects generally increasing precipitation. Y'all let's show precipitation increase the way if we have salt plus strong acid or strong base.

[00:08:32]And decreases ionization.

[00:08:35]How? If we have salt plus weak acid or weak base. Class. How are you all doing?

[00:08:43]So, common ion promotes precipitation.

[00:08:45][snorts] Common ion decreases ionization.

[00:08:52]Come on. Common ion effects increasing precipitation Let's explain the common ion effect for each of the followings.

[00:09:10]Example, we have HF.

[00:09:13]If HF is added to a solution of KF.

[00:09:17]Last time I said if KF is added to water.

[00:09:23]One salt is added to water. This is salt hydrolysis, but now we have two substances. This is a common ion. Okay.

[00:09:33]If HF gas is bubbled into a solution of KF or if HF solution is added to a solution of KF or if KF is added to HF solution.

[00:09:45]So, explain everything. Okay.

[00:09:48]First of all, since we have two substances, it means the question is related to the common ion effect. So, write the reaction for both first of all. We have HF and KF.

[00:10:04]Come on.

[00:10:05]This is a weak acid. Wait a minute. This is any weak acid.

[00:10:11]KF salt.

[00:10:14]Yallah, write the reaction for both.

[00:10:17]HF + H2O reversible the way that see H3O + F negative. True?

[00:10:27]How about the salt?

[00:10:29]The salt is undergo the dissociation reaction to form K + and F negative.

[00:10:38]Good? Yallah.

[00:10:39]Two substances. If the acid or base is weak, which one will reverse it? The weak one. Aha.

[00:10:45]Yeah, come step. First step, please.

[00:10:49]Try to check for the common ion. Is there any common ion? Yeah.

[00:10:53]We have a common ion.

[00:10:55]Good.

[00:10:56]Common ion.

[00:10:57]Yallah, we need which reaction between these two?

[00:11:02]The one that is weak. The one that is reversible. So, we need this reaction.

[00:11:07]Okay? Aha.

[00:11:11]So, now common ion man here also then the sky again, we will go farther. We need this reaction.

[00:11:18]This reaction has four parts. One, two, three, four.

[00:11:28]One, two, three, four. All of them are increased.

[00:11:33]All of them are increased, but the neighbor of the common ion is decreased.

[00:11:39]Okay? Look. The lazy favors reverse.

[00:11:47]Reverse for what? For HF.

[00:11:50]Which is a weak acid. Okay, if the weak one is reversed, the lazy ionization ionization silly day decrease the baby.

[00:12:00]Okay, let them go away. Try to write all of them in the desired reaction. HF man here.

[00:12:09]H2O man here.

[00:12:11]We don't need the concentration brackets for the H2O, okay? Because it's a liquid substance. H3O man here.

[00:12:20]And F negative is man here. Okay.

[00:12:24]First of all, common ion is always increased.

[00:12:27]Mhm.

[00:12:28]All of them are increased. Only the one that locates beside of the common ion is decreased. All common ion in your baby, man.

[00:12:36]Which one is the neighbor of this? H3O.

[00:12:38]Only the neighbor of the common ion is decreased.

[00:12:41]All of them are increased. Okay?

[00:12:45]H3O is decreased. Number of H2O is increased. Concentration is increased.

[00:12:51]Since H3O is decreased, so pH is increased.

[00:12:55]Class, I will be noticed it too.

[00:12:58]What a what a what a what a what a what a what a child like a headache in water.

[00:13:02]Born on the moon, I say it weak a huh.

[00:13:05]If NH4Cl is added to a solution of NH3.

[00:13:12]Aha, this is a common ion. We have two substances. So, first write their reactions. Okay? Aha. NH4Cl.

[00:13:23]The salt is dissociated.

[00:13:28]Plus Cl negative. How about this NH3?

[00:13:33]NH3 plus H2O reversible the beta NH4 plus OH negative.

[00:13:41]First of all, check for the common ion.

[00:13:43]Is there any common ion? Yes.

[00:13:46]Good. Then go farther to see the effect of the common ion.

[00:13:50]If there's no common ion, just say no common ion. Nothing happens. We don't talk about the about the question about the the situation, anything, okay?

[00:14:00]First, we need to have the common ion.

[00:14:02]Okay.

[00:14:03]Then, one of them must be reversed.

[00:14:06]Which one is reversed? Since the base is weak, so the base is reversed. We need this reaction Omani sphere, the one that's going to be reversed.

[00:14:19]This reaction has four substances.

[00:14:24]All of them are increased, but the neighbor of the common ion is decreased.

[00:14:28]This is the common ion. So, this is increased, increased, increased. Only the neighbor of the common ion is decreased.

[00:14:47]Our reaction Because of the Le Chatelier's principle, of course.

[00:14:54]I'm not going to talk about that thing again.

[00:14:57]Okay, the Le Chatelier's favors reverse for NH3.

[00:15:04]For NH3, okay?

[00:15:10]Ionization decreases.

[00:15:12]Yeah, let's write down the substances right here. NH3 H2O number, of course, number of H2O molecules NH4 and what and OH negative.

[00:15:30]Okay, yep.

[00:15:33]All of them are increased but the number of the common ion is decreased.

[00:15:36]Increased number of H2O molecules increase increase since OH is decreased so pH is also decreased.

[00:15:48]Common ion here it makes my body reaction here.

[00:16:02]Let's have another question. You said it like that.

[00:16:07]CH3 COONA plus it by CH3 COOH.

[00:16:15]Aha, we have two substances. So again this is a common ion effect. Identify the types of the substances. This is a salt and this is a weak acid.

[00:16:26]So the weak one must be reversed.

[00:16:30]CH3COOH plus it by H2O.

[00:16:36]CH3COO negative plus H 3O. How about this?

[00:16:45]>> [snorts] >> CH3COONA dissociated to form what?

[00:16:54]CH3 COO negative plus NA plus. Good. Which one is reversed? The one that is reversible. The one that is weak. So we need this reaction but Mr. We have skipped one point. First check for the common ion to see the effect of the common ion. Is there any common ion?

[00:17:13]Yep.

[00:17:14]So we need this reaction.

[00:17:17]How many substances are there? One, two, three, four. All of them are increased, but the neighbor of the common ion is decreased.

[00:17:27]First thing, the common ion is increased. Number of H2O molecule is increased. This one is increased, but H3O is decreased, then pH is increased.

[00:17:46]NaCl plus HCl. I've seen this too many times in Wizary. The question said, "If hydrogen chloride gas is bubbled into a solution of such in into a saturated solution of NaCl."

[00:18:01]This is a salt, and this one is a strong acid.

[00:18:07]Okay?

[00:18:14]Say the error. Say error error.

[00:18:17]NaCl the beta Na plus Cl negative. HCl, it's a strong acid, be careful.

[00:18:26]Be careful.

[00:18:27]Okay, we need a direct arrow again to form H3O and Cl negative. Yallah.

[00:18:35]If the acid is strong, which one is reversed?

[00:18:38]The salt. So, just add the reverse direction for the salt. The salt will be reversed. So, first of all, check for the common ion then. There's a common ion. In this case, we need which reaction between these two? The salt. We need this reaction. Because the acid is strong, or if the base is strong, we need the salt. Okay, yallah. How many substances are there right here?

[00:19:05]Three.

[00:19:06]All of them are increased, but the neighbor of the common ion is decreased.

[00:19:09]Which one is the common ion? Cl.

[00:19:12]Okay, so all of them are increased. Only the neighbor of the common ion is decreased. So, in this case we will say precipitation is increased. It means the amount of NaCl, but not the concentration. Okay?

[00:19:26]Look. Na is decreased and Cl negative is increased.

[00:19:48]KBr plus by HF. Okay? Let's write the reactions.

[00:20:00]The beta T K plus Br negative. Okay? K plus Br negative. How about HF?

[00:20:09]Huh? HF plus by H2O to form H3O plus by F negative.

[00:20:19]HF is a weak acid, so this one will be reversed. First, we have to see the common ion. Then we will see the effect of the common ion. Is there any common ion here? Of course not.

[00:20:30]So, there is no common ion between them.

[00:20:32]Just say no common. Class.

[00:20:35]That's all.

[00:20:36]No common ion between them.

[00:20:45]Explain the effect of the common ion in each of the following pairs. So, I have explained all things right here. Look at this question.

[00:20:54]Put a star here like this. Okay.

[00:21:05]NaOH and C2H5OH or CH3OH.

[00:21:11]These two are alcohols.

[00:21:13]Alcohols, we'll get back to them in chapter 10. They're non-electrolytes.

[00:21:18]So, they don't provide any ions. So, just say no common ion, okay? Because for the common ion, the two substances must be electrolytes.

[00:21:29]Oh, and I'm going to go back to the We don't need the forward direction, by the way, here.

[00:21:34]We only need the reverse direction.

[00:21:36]Types of common ion, we have three types.

[00:21:40]The three types are if we have a weak acid or if we have a weak base or strong acid and strong base with the salt. If we have a weak acid plus its salt, also called weak acid and it is salt.

[00:22:03]I will show you the 20 billion. Weak acid is added to a solution of its salt.

[00:22:08]So, which one will be reversed? The weak one will be reversed. Ionization see later decrease a bit because the reverse one is the acid. H3O is decreased, pH is increased. Khallas. Yallah, which one is reversed? We have a weak acid plus weak base plus acidic salt. The weak one will be reversed. Ionization see later decrease a bit, OH decrease a bit.

[00:22:28]Khallas.

[00:22:42]And if you have a strong acid or strong base, in this case, the salt will be reversed, okay? So, just say precipitation is increased and dissociation is decreased. Khallas.

[00:23:07]>> Same example does it a basket D?

[00:23:42]First of all, since we have two substances, so this is a common ion effect.

[00:23:49]Common ion, very good.

[00:23:52]For the common ion, just identify type of the substances. NH4Cl It's a salt, right?

[00:24:07]The latest yellow NH4 plus what? Cl negative. How about it?

[00:24:12]NH3 It's a weak acid plus it by H2O to form NH4 plus OH negative. Is there any common ion between them? Yep. It's here. Which one will be reversed?

[00:24:29]The weak one will be reversed.

[00:24:31]How many parts are here? Four parts.

[00:24:35]Okay, ionization silly day.

[00:24:38]Ionization is decreased. Concentration of NH3 is increased. H All of them are increased, but the neighbor of the common ion is decreased.

[00:24:50]So, OH is decreased.

[00:24:53]pH is decreased and the NH4 is increased.

[00:24:58]Class, I have to Increases pH.

[00:25:07]pH and ionization are both decreased.

[00:25:13]pH is decreased. Well, they are all right.

[00:25:17]Decreases pH.

[00:25:22]pH and ionization are both increased.

[00:25:24]Oh, I don't care.

[00:25:25]So, all of them are coming in. B, of course.

[00:25:32]Yallah, this is a basic salt.

[00:25:37]Plus a weak acid.

[00:25:40]I'll leave this for you.

[00:25:45]When an amount of a hydrogen chloride or hydrochloric acid, if it's aqueous, of course, is added to a saturated solution of NaCl.

[00:25:59]Or NaCl, the beta.

[00:26:02]Na plus a beta.

[00:26:06]Cl negative, of course.

[00:26:08]And yeah, HCl is one here.

[00:26:11]Plus H2O.

[00:26:13]The beta.

[00:26:14]H3O plus Cl negative. Good.

[00:26:19]I keep the hour. Yallah, which one will be reversed? No, mister. We have to to to have the effect of the common ion, huh?

[00:26:30]Okay. The acid is strong, so the salt will be reversed. We have three parts here.

[00:26:37]All of them are increased, but the neighbor of the common ion is decreased.

[00:26:41]So, precipitation is increased.

[00:26:45]Dissociation is decreased. Cl as the common ion is increased. Na is decreased.

[00:26:54]I got it.

[00:26:57]NaCl is precipitated or acid HCl is precipitated to water going in the head.

[00:27:03]Eh, ionization of HCl is increased. No.

[00:27:06]No. No. No. No. No.

[00:27:17]Question six. Asterix is one NaCl will precipitate in in the solution of what? First of all, it's a salt.

[00:27:29]How to precipitate out a salt? If we add a strong acid or a strong base. But, there must be a common ion, right? Okay.

[00:27:39]HBr, it's a strong acid.

[00:27:42]Well, based on the strength, it can be.

[00:27:45]HCl is a strong acid, also. And NaOH is a strong acid, but we only need the one that has that has a common ion with it. There's no common ion between this and the salt. No common.

[00:28:00]Otherwise, this is will be correct.

[00:28:03]Yeah, there's a common ion between them and there's a common ion between them.

[00:28:07]The correct answer is D, B and C.

[00:28:10]Okay? And common ion is a consequence of the Le Chatelier principle. You know this.

[00:28:16]I've solved this question 100 times.

[00:28:19]It's time for the buffer solution, but not today. I'm sorry. I just for the title, it's it's time. Otherwise, in the next lesson, I'm going to explain the buffer solution.

[00:28:29]So, Inshallah, I'm pretty sure you will feel good with this.