Elemental Analysis (To determine the element present in organic compound) . Episode 2

[00:00:00]All right.

[00:00:02]Good afternoon, students.

[00:00:04]This is White Faraday.

[00:00:08]In this video, I want to explain this practical, which is called elemental analysis.

[00:00:18]Elemental analysis for the purpose of this examination.

[00:00:23]Elemental analysis, this is used to identify the elements present in an organic compound.

[00:00:31]Once you hear elemental analysis, you should know that it is used to identify the elements that are present in organic compounds.

[00:00:45]So, some of the elements that we are going to identify today, some of the elements, some of the elements that we are going to identify will be nitrogen.

[00:01:00]We are going to see how nitrogen is present in an organic compound.

[00:01:06]We also talk about halogens.

[00:01:10]Halogens.

[00:01:13]Under these halogens, we are going to identify for chlorine.

[00:01:22]We have bromine.

[00:01:26]We equally have uh iodine.

[00:01:31]So, these are the three So, these are the three These are the three elements under halogen.

[00:01:45]This is number two.

[00:01:47]We also going to talk about how we can identify this element that is called sulfur.

[00:01:56]Sulfur.

[00:01:58]Talk about oxygen. How to know when oxygen is present.

[00:02:04]We talk about hydrogen.

[00:02:10]ETC. So, these are the basic ones that we are going to discuss briefly for your understanding. So, let's quickly take the first one. Let us assume that an organic compound X is given to you and you want to know if it contains chlorine, bromine, or iodine.

[00:02:31]Now, let me quickly remind us that in each of these that you want to identify, there is a particular special agent that you can use to confirm that.

[00:02:42]And this test This test is called a Lassigne test. This test is called a Lassigne test. That is how we can obtain this. Lassigne test.

[00:02:56]Okay. So, we pick the first one, which is halogen.

[00:03:00]Let's talk about halogen.

[00:03:02]Now, for halogen, for halogen, I want to use this particular test, which is Lassigne test to confirm the presence of halogen.

[00:03:14]The reagent The reagent that I will use is a special reagent and that reagent is called silver nitrate.

[00:03:27]So, we are going to use silver nitrate in the presence of what?

[00:03:32]Dilute HNO3.

[00:03:36]This is the reagent that I'm going to use.

[00:03:39]So, this reagent is AgNO3.

[00:03:43]Then, plus what? Dilute HNO3.

[00:03:49]So, what you should do as a student is to know that this particular reagent is used to confirm the presence of sulfur in large in text.

[00:03:59]When a particular organic compound is given to you and you want to identify it.

[00:04:04]So, if I have example of organic compound if I have example of organic compound sample of organic compound and then plus you have this AgNO3.

[00:04:22]Once you have this AgNO3 and then plus this HNO3.

[00:04:31]This is an acid.

[00:04:33]And then you confirm a precipitate.

[00:04:37]If there is precipitate if there is precipitate if there is precipitate I don't want us to know whether if it is white or blue or green or yellow.

[00:04:51]But as long as there is a precipitate, you should know that halogen is present.

[00:04:59]So, if precipitate is formed if a precipitate is formed we should know that what? Halogen is present.

[00:05:07]Precipitate formed we show off that there is what? Halogen.

[00:05:14]But if there is no precipitate formed what we are going to report in our inference is that halogen is absent because this is what I normally use to confirm for the presence of halogen when it is talking about a large in text.

[00:05:32]Okay?

[00:05:34]So, for instance for the precipitate that I you're going to see here can be white precipitate.

[00:05:43]It can be yellow precipitate.

[00:05:46]It can also be what? Pale yellow.

[00:05:51]It can also be pale yellow.

[00:05:53]So, for white precipitate, you are going to confirm chlorine.

[00:06:01]And then for yellow precipitate, for your yellow precipitate, just when you have only yellow precipitate, you are going to confirm what? Iodine.

[00:06:15]And then for pale yellow, you confirm what? You are going to confirm this, bromine.

[00:06:21]And also remember that we are going to use ammonia to know whether the precipitate will dissolve in each of these.

[00:06:29]We're going to use ammonia to know whether the precipitate will dissolve in each of these.

[00:06:36]So, if I use ammonia, the essence of this ammonia is to know whether the precipitate will dissolve.

[00:06:42]But note that in chlorine, the precipitate will dissolve.

[00:06:46]The precipitate will do what? Will dissolve for chlorine.

[00:06:51]And then also for bromine, the precipitate will also dissolve, but it is slightly soluble.

[00:06:58]It's slightly soluble.

[00:07:00]But we are going to also say that it dissolves.

[00:07:03]Then for iodine, it is insoluble. The precipitate is going to be insoluble.

[00:07:10]So, which means that the presence of ammonia is used to confirm whether the precipitate will dissolve or the precipitate will not dissolve.

[00:07:21]Now, let's look at this. Let's look at the first one.

[00:07:26]I have that example of the organic compound, example of the organic compound plus silver nitrate plus this acid.

[00:07:36]And let's assume that what I have is a precipitate.

[00:07:39]And maybe it is a white precipitate that is formed. Let me just say I have precipitate observed.

[00:07:48]So, precipitate observed.

[00:07:53]Please, avoid writing it as PPT.

[00:07:56]So, when we say precipitate observed in my inference, I'm going to write what?

[00:08:03]Halogen is present.

[00:08:08]That's what I'm going to write.

[00:08:10]Halogen is present. Why is halogen present?

[00:08:13]Because a precipitate is formed. Now, if I put this in this particular this I can also put write the precipitate that is formed. If it is white precipitate, I can write it.

[00:08:27]Okay, let me now further confirm this.

[00:08:30]Let me just say white precipitate observed.

[00:08:33]Mhm?

[00:08:35]Let's say white precipitate observed.

[00:08:37]What am I confirming? Halogen present.

[00:08:40]And sample of Ag plus this plus this, I will now have that the white precipitate the white precipitate, as we know, white precipitate is going to dissolve.

[00:08:55]White precipitate soluble.

[00:09:00]So, it's going to be that white precipitate is what? Soluble.

[00:09:04]And because the white precipitate is soluble what am I going to have? Chlorine.

[00:09:13]Chlorine.

[00:09:14]I will say chlorine is present.

[00:09:19]So, what I will confirm is that chlorine is what? Present.

[00:09:23]Because I have a white precipitate that is soluble.

[00:09:28]So, if the white precipitate is soluble, what I will confirm is chlorine.

[00:09:33]And let's also have this.

[00:09:36]Let us have the second one.

[00:09:38]Let me have this and then I will have a yellow precipitate, okay?

[00:09:42]Let's have yellow precipitates.

[00:09:50]Let's have yellow precipitates observed.

[00:09:54]What am I still going to write? It's still halogen present.

[00:10:01]I'm also going to write halogen present.

[00:10:06]So, if halogen is present and then I want to know whether the precipitate will dissolve in the presence of ammonia. Remember I said that white precipitate indicates the presence of chlorine, which is soluble.

[00:10:19]And then yellow precipitate indicates that what I have is iodine.

[00:10:26]And it is what, somebody? Insoluble.

[00:10:29]So, what I will now have is This is yellow precipitate. I will say yellow precipitates.

[00:10:40]Yellow precipitates insoluble.

[00:10:46]So, what am I going to confirm?

[00:10:48]I'm going to confirm iodine present.

[00:10:54]I'm going to confirm that it is iodine that is present.

[00:10:58]That's exactly what I'm going to confirm.

[00:11:02]So, when you look at it you see that this is very simple to understand.

[00:11:08]Here, I have that this is sample AgNO.

[00:11:12]This is what I'm going to confirm.

[00:11:14]And this is exactly what I'm going to confirm.

[00:11:16]And also lastly when you talk about the last one which it's pale yellow.

[00:11:24]The pale yellow that indicate the presence of bromine you're also going to be having it to be slightly soluble.

[00:11:32]You're going to have it to be slightly soluble, okay?

[00:11:36]So, it's going to be slightly soluble.

[00:11:39]It's going to be slightly soluble.

[00:11:42]When you take something like bromine, you are having [clears throat] it to be slightly soluble.

[00:11:48]So, which means that summary is that we use AgNO3 in the presence of HNO3 to confirm once there is a precipitate, you know it is halogen.

[00:12:01]White precipitate.

[00:12:04]White precipitate.

[00:12:06]Soluble in ammonia.

[00:12:11]We confirm what?

[00:12:12]We're going to confirm chlorine.

[00:12:16]And when you have a yellow precipitate.

[00:12:21]Yellow precipitate.

[00:12:24]When you have yellow precipitate, insoluble in ammonia.

[00:12:32]What are we going to confirm?

[00:12:35]What are we going to confirm? We confirm iodine.

[00:12:39]And when you have pale yellow.

[00:12:43]Pale yellow precipitate.

[00:12:46]Soluble. Remember it is slightly soluble or you can say slightly soluble in ammonia.

[00:12:56]What are we confirming?

[00:12:58]We are confirming bromine.

[00:13:02]So, this is actually the test you can use to confirm if halogens are present in organic compound.

[00:13:09]All right, let's talk about the second test, which is test for nitrogen.

[00:13:14]Test for nitrogen.

[00:13:16]This is also talking about Lassaigne what? Test.

[00:13:21]This is also Lassaigne's test.

[00:13:24]It's also Lassaigne's test.

[00:13:28]If they ask you to use Lassaigne's test, you know that this is what they are talking about.

[00:13:33]So, if you want to confirm the presence of nitrogen in organic compound, you're going to use Beilstein agent. Any place you see Beilstein agent, any place you see Beilstein agent, in the presence of H 2 SO4.

[00:13:51]Or they may decide to replace Beilstein agent because this particular acid is somehow acidic.

[00:14:02]It's more acidic. We can say it is more corrosive. So, in most times in the lab, they replace that with HCN.

[00:14:11]So, you may see something like HCN.

[00:14:14]They may use HCN in the lab. I think this is also important.

[00:14:20]So, whenever you are using this and you confirm the presence of something like uh let me say greenish solution. If you confirm a greenish solution, if you confirm a greenish solution, you should know that nitrogen is present.

[00:14:40]Another way to confirm that greenish solution is to talk about a deep Prussian precipitate. We can say deep Prussian blue.

[00:14:51]Most of you know this.

[00:14:53]You can use a deep Prussian blue to also confirm the presence of nitrogen.

[00:15:01]So, you should know that Beilstein agent here is used to confirm for the presence of what? Nitrogen.

[00:15:08]So, if there is no reaction or no visible reaction, your inference should be nitrogen is abs- Your inference should be nitrogen is what?

[00:15:20]It's absent. That is exactly what you are going to have. And then sometimes in exam, they will just give you this solution plus the sample.

[00:15:33]And when you check it, you are going to have something like greenish solution or you have greenish solution.

[00:15:41]This also confirms that nitrogen is also present.

[00:15:46]This confirms that nitrogen is present.

[00:15:49]And then for you to have a deep Prussian blue, they cannot say add this plus what? HCN. In this case, you are going to have a deep Prussian what? Blue precipitates.

[00:16:06]That's what you are going to be having.

[00:16:08]But if you mix this with a sample, what you are going to observe is just a greenish solution.

[00:16:14]Then when you acidify it with this particular acid, you have a deep Prussian what? Blue. That's exactly what you are going to be having.

[00:16:23]So but if you add this and then what you see is not greenish, you saw something like a pale yellow or a different thing altogether, it simply means that nitrogen is absent in that particular organic compound.

[00:16:40]While you are watching this, I want you to subscribe to this my YouTube channel if you have not done that.

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[00:16:53]This year will be the last year I'm going to be posting practical videos in this YouTube. Next year, I will organize In fact, next year, I'm not going to post any video on my practicals. Those people that is coming. So this year, you guys are lucky. Okay?

[00:17:14]Because I'm going to delete all these videos.

[00:17:17]All right.

[00:17:19]So, So, let's talk about number three.

[00:17:23]Let's discuss number three, which is what? Sulfur.

[00:17:27]I want to know how we can identify sulfur in organic compound.

[00:17:32]To identify sulfur in organic compound, we are going to use two reagents.

[00:17:40]Which I'll give you one.

[00:17:42]One is that when you put the sample that you are suspecting in the presence of what?

[00:17:51]Acetic acid.

[00:17:54]And then followed by what? Lead.

[00:17:57]Lead what? Acetate.

[00:18:00]This is what you are going to use for sulfur.

[00:18:03]I would want you to also use this lead to remember that it will give us a black precipitate. Anytime you see lead acetate, you know that you are targeting a black precipitate.

[00:18:14]So, when there is a black When there is a black precipitate formed, what you are going to write in your inference is that sulfur is that sulfur is what? Present.

[00:18:33]But if in the presence of this sample now, sorry, this reagent, and there is no black precipitate, in fact, no visible reaction, your inference should be that sulfur is absent in the sample.

[00:18:49]Reason is because this is only used to identify This is used to identify whether sulfur is present or not.

[00:18:58]So, if there is no reaction, what I'm going to write is no visible what?

[00:19:03]Sorry, what I'm going to write is sulfur is absent in that particular organic compound.

[00:19:10]So, let's talk about Also, for sulfur, Remember I said there are two types of for sulfur we can use another reagent and that reagent is sodium nitroprusside.

[00:19:23]Anytime you see this sodium nitroprusside you should know that it is used to identify the presence of sulfur in organic sample.

[00:19:32]So when you have a sample let's say sample plus sodium nitroprusside.

[00:19:44]When there is sodium nitroprusside and you observe a precipitate like you observe a violet slash purple.

[00:19:56]Purple PPT.

[00:19:58]Once you have this as violet slash purple PPT, you should know that sulfur is also what? Present.

[00:20:07]So which means that there are two reagents that I can use to confirm sulfur in elemental analysis.

[00:20:13]The two reagents are one the two reagents are one you can use acetic acid.

[00:20:23]Acetic acid plus what? Lead acetate.

[00:20:30]This one shows black precipitate black.

[00:20:34]Then number two is that you can use what?

[00:20:37]Sodium nitroprusside.

[00:20:39]Prusside.

[00:20:43]This one shows what? Purple.

[00:20:46]Or you have something like a violet what?

[00:20:50]Color.

[00:20:52]So if there is no purple color or violet color on this, you should know that sulfur is absent.

[00:20:59]Okay, let's quickly look at this past question.

[00:21:03]Let's look at this past question that was asked.

[00:21:06]Let's solve it.

[00:21:08]And in this case, I'm going to be using shortcut to provide the answer.

[00:21:12]Just like I am in the lab. But make sure that anything you see in the lab, that's exactly what you are going to write.

[00:21:19]Now, examiner says sample Y is an organic compound. Name the element present in Y.

[00:21:26]Name the element present in what? In Y.

[00:21:30]Don't worry, we are going to solve that past question last.

[00:21:33]I'm going to solve that one last. Let's solve this one.

[00:21:37]Let's solve this one so that at the end you observe it. This one says sample X is organic compound. Name the element present in X.

[00:21:45]Now, I want to just assume that my X, the element that is present in X is nitrogen.

[00:21:54]That is what I want to assume. That it is nitrogen. So, what am I going to say?

[00:21:59]We start. I'm not going to waste much time. Sample X plus FeSO4, what am I going to have? I will have greenish.

[00:22:09]I will have a greenish solution.

[00:22:14]Observe. That's what I'm going to have.

[00:22:17]Okay?

[00:22:19]So, if greenish solution is observed, what is my What will be my inference?

[00:22:25]I'm going to write nitrogen.

[00:22:29]Nitrogen present.

[00:22:32]If you like, you can use suspected.

[00:22:35]Now, this first sample X plus this, and then in the presence of FeCN, the essence of acidifying this is to see whether if I'm going to have a deep Prussian what? Precipitate.

[00:22:47]So, I will now have deep Prussian blue precipitate formed.

[00:23:03]So, what am I going to also have in?

[00:23:06]I will write nitrogen present.

[00:23:12]Remember, I want to show the examiner that what is present is nitrogen.

[00:23:16]So, it means that if I go to the next next reaction, this one, example, X plus acetic acid.

[00:23:24]What am I going to be having?

[00:23:26]I will have no visible reaction because I've confirmed nitrogen already.

[00:23:30]I'm going to have no visible reaction.

[00:23:33]Except if the compound contains nitrogen, and it also contains something like a sulfur. Something like that can happen.

[00:23:42]A A sub- A sorry, a compound can contain nitrogen, and it can also contain something like sulfur. Yes, it is possible. So, that is why I said, you you if you want to change this to sulfur, that is no problem.

[00:23:55]But, let's assume that what I'm having So, if it is only nitrogen that I'm having, what is here is no visible reaction.

[00:24:07]This is no visible reaction, right?

[00:24:10]And I want to ask you, what do we normally use this test to confirm? We use this to confirm the presence of sulfur, right? So, what I will write here is that sulfur sulfur is absent.

[00:24:26]That's what I'm going to write.

[00:24:28]Now, look at it. Sample X again plus sodium nitroprusside.

[00:24:33]We use nitroprusside also to confirm the presence of sulfur.

[00:24:38]So, I'm equally going to have no visible reaction.

[00:24:43]No visible reaction.

[00:24:45]We also write sulfur is absent. That's what I'm going to write.

[00:24:53]And then, can I ask you, what do we normally use this to confirm?

[00:24:59]So, what do we normally use this to confirm, class?

[00:25:01]We use this to confirm the presence of halogen. Okay, let me have in that compound, I want to have that organic compound contains nitrogen, and it also contains something like uh what is it called? Chlorine.

[00:25:13]I want to just assume that. But, if I don't want to assume that, I can complete it and say no visible reaction here. No visible reaction here. Then, halogen absent. Halogen absent. But, let me just say that in this case, I have nitrogen and I have chlorine. So, what I'm going to write is that sample X here, that will be reaction.

[00:25:36]So, I'm going to have white precipitates.

[00:25:41]White precipitates. That's what I'm going to be having. White precipitate, okay?

[00:25:47]White precipitate. And what am I having here?

[00:25:51]Halogen is present.

[00:25:55]Halogen is present. That's what I'm going to be having.

[00:25:59]Now, in this case, sample X plus this The essence of this is to say whether if it will dissolve.

[00:26:05]So, I'm going to have that the white precipitates white precipitate dissolves.

[00:26:16]Are you getting it? Or we can say white precipitate dissolves.

[00:26:24]It dissolves. So, what am I going to write here?

[00:26:27]I'll write that chlorine is present.

[00:26:34]Chlorine is present.

[00:26:36]Now, in this case the examiner will score me my That person will give me my mark.

[00:26:42]Though I have confirmed two uh what is it called? I've confirmed two element here. One is nitrogen, and another one is what? Chlorine.

[00:26:54]But it will be better for you. Just confirm only one element and then you go straight to the point. Remember I said you must write exactly anything that you confirm. So, what you are going to write is that sample X sample X contains nitrogen and the what? Chlorine.

[00:27:19]But when you write this, you are correct.

[00:27:22]Sample X contains nitrogen and chlorine.

[00:27:24]You can equally just assume that it is only nitrogen that it contains. In that case, no visible reaction, no visible reaction.

[00:27:33]That is just what you can confirm.

[00:27:37]All right, let's look at the second question.

[00:27:39]I want to use the second question. In this case, sample A is an organic compound. Name the element present in A.

[00:27:46]Now, let me just assume here that my element is halogen.

[00:27:50]I want to have halogen. I don't want to perform the experiment. I just want to write it and the examiner will give me my score.

[00:27:56]So, since it is halogen Okay, since I'm talking about halogen, which one am I thinking of? Let's go for yellow, the one that will give me a yellow precipitate.

[00:28:05]I can have a pale Let's have pale yellow.

[00:28:13]Pale yellow precipitate here.

[00:28:17]Now, a pale yellow precipitate here in the presence of this. What am I going to write? I'll write that nitrogen is absent.

[00:28:29]Why did I write that nitrogen is absent?

[00:28:32]It's because this is used to confirm the presence of nitrogen, right?

[00:28:37]So, also I will also have that yellow precipitate.

[00:28:46]I will also have yellow precipitate here whether if it dissolve or it did not dissolve. Okay, let me say dissolves.

[00:28:54]Let's say it dissolves.

[00:28:56]And then what am I having? I will still write nitrogen is absent.

[00:29:04]The only way it will give me that nitrogen is present is only when this is giving me a deep blue or a greenish solution.

[00:29:13]So, we go to the next one. Remember, I want to confirm chlorine. Sorry, I want to confirm any of the halogen like bromine or iodine.

[00:29:22]So, let's have this. What am I going to have here?

[00:29:25]No visible reaction.

[00:29:31]When I have no visible reaction, what is absent? Sulfur.

[00:29:38]Sulfur is absent here.

[00:29:42]So, sulfur is absent here.

[00:29:45]And this is also used to confirm for sulfur.

[00:29:48]I will also have no visible reaction.

[00:29:55]What am I having?

[00:29:57]I will still say that sulfur absent.

[00:30:03]I want to be fast.

[00:30:05]Now, what is this used to confirm? This is used to confirm the presence of the halogen.

[00:30:12]So, I'm going to have yellow precipitate.

[00:30:21]What am I having?

[00:30:23]Halogen present.

[00:30:28]So, if I have that yellow precipitate in the presence of ammonia, let's see whether if it is going to dissolve or whether if it's going to be insoluble.

[00:30:37]Let's see whether if it's going to dissolve. Let's say yellow precipitate insoluble.

[00:30:42]Let's assume that the yellow precipitate precipitate insoluble.

[00:30:53]So, if the yellow precipitate is insoluble, what am I confirming?

[00:30:58]I will say iodine present.

[00:31:04]So, by so doing, the examiner will score me my mark. This is This is what I have.

[00:31:12]And the examiner will just give me my mark.

[00:31:15]Okay?

[00:31:17]All right, look at this. Look at this.

[00:31:19]This is likely exam question.

[00:31:22]Sample Y is an organic compound. Name the element present in Y.

[00:31:28]Now, they said sample Y plus water one above with universal indicator.

[00:31:36]Sample Y plus acetic acid.

[00:31:40]So, the essence of this acetic acid and this is to confirm whether there is a sulfur there.

[00:31:47]And this last one is to confirm whether if there is halogen.

[00:31:51]So, now, remember I said anything you see in the lab, make sure you write it.

[00:31:56]But, if I just assume that here, and then it is miscible.

[00:32:02]If I assume it is miscible, my inference will be that sample Sample Y is polar.

[00:32:16]Okay?

[00:32:17]Then above, let's Let me assume that it turn red.

[00:32:24]If it turn red, what can we say?

[00:32:27]We say that sample Y is acidic compound.

[00:32:35]These things are assumption. I can even decide to make it to be neutral.

[00:32:39]But I'm going into acidic because I want to talk about acid chloride.

[00:32:44]Now, sample Y plus acetic acid plus this.

[00:32:49]No visible reaction.

[00:32:55]So, because there is no visible reaction, what is absent is sulfur.

[00:33:02]Sulfur is absent.

[00:33:06]Here, I have sample Y plus this. I'm equally going to have no visible reaction.

[00:33:13]Because I want to confirm chlorine. No visible reaction.

[00:33:19]I will also say sulfur is absent.

[00:33:26]And then finally, I'm going to have this.

[00:33:31]So, I'm going to have white precipitates formed.

[00:33:42]What am I having?

[00:33:44]Halogen is present.

[00:33:52]So, if halogen is present, what halogen is there? Above plus this.

[00:33:58]If you put this ammonia, you're going to have white precipitates.

[00:34:06]Will it dissolve?

[00:34:08]Precipitates soluble.

[00:34:13]Or you can say dissolve. So, chlorine is present.

[00:34:21]So, in this case, this is what I have.

[00:34:25]Within a space of 3 seconds or 3 minutes, I've gotten my answer. I can now conclude that sample Y Sample Y contain chlorine as an element.

[00:34:43]You can say sample Y contains chlorine, full stop.

[00:34:47]So, this is exactly how we can solve this.

[00:34:50]So, please, I would want you to also watch our next episode on functional groups.

[00:34:58]Make sure you share this video, like the video, and thank me later.

[00:35:03]If you want to join my revision class, you can come to my class and join us.

[00:35:08]You can also call me on 070 36 22 14 32.

[00:35:19]Thank you, and God bless you.

[00:35:22]I love you guys.

[00:35:23]Bye-bye.