Calculating MOLE CONCEPT OLEVEL S4

Added: 2026-06-02

[00:00:02]Yes, scholars, you're welcome to the class that you're going to have.

[00:00:08]So, in this class, we are going to speak of mole concept.

[00:00:13]And uh that's the next topic that I had promised you that you're going to look at.

[00:00:20]But uh you still know that norms whenever we start classes, we have some new people that join us.

[00:00:27]So, in about a half a minute, that's what, 30 seconds, allow me to introduce myself to those that don't know me.

[00:00:38]Yes. So, those that don't know me, uh my name is simply written here.

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[00:02:51]So, number one, um we are saying we are dealing with a topic known as mole concept, and this is the first lesson.

[00:03:01]Our topic is known as mole concept. So, before we derive into any topic, it's always good to have a knowledge of what it is really talking about or at what it majorly constitutes of.

[00:03:15]So, whenever I hear a word mole concept in a simple way.

[00:03:21]So, mole concept mole concept in a simple way in a simple way can be defined can simply be defined as the method or concept as the method or concept used in chemistry Used in chemistry. How do we use it?

[00:03:58]To know the weight of substances.

[00:04:03]To know the weight of substances.

[00:04:09]Hope that is very clear to everyone.

[00:04:12]Now, there are other definitions that you can outtake by the sake of the subject.

[00:04:19]Yes.

[00:04:21]But this is in a simple way. How easily my friend Jimmy can understand what mole concept is. How easily James can understand what mole concept is.

[00:04:33]So, mole concept, I've said, this is a simple way.

[00:04:40]Oh, sorry. In a simple way, this can be defined as a method or concept.

[00:04:47]Can be defined as a method or concept used specifically in chemistry to do what? To know the weight of substances.

[00:05:01]Okay? So, first, we use this method known as mole concept in chemistry to know the weight of substances.

[00:05:10]Let me highlight it such that everyone can see.

[00:05:14]This is what we are defining, mole concept.

[00:05:18]Okay? Now, different subjects have gotten different ways on how they know the weight of their substances.

[00:05:26]For example, if you're going to go to the side of, for example, subjects like physics. Let me write here.

[00:05:34]Subjects like physics or you can speak of subjects like mathematics.

[00:05:43]Math. I know everyone here does math.

[00:05:45]So, when you go to those subjects, you're going to see that these subjects, they also have the different ways they know the weight of their substances.

[00:05:55]For these two subjects, they usually use a method.

[00:06:00]Number one, use of weighing scales.

[00:06:04]Uh let me solve our time. So, these subjects, number one, they use weighing scales.

[00:06:12]Um some of them use a beam balances.

[00:06:16]There's what we call beam balances.

[00:06:19]Then spring balances. I hope you people know this.

[00:06:23]And what is the major end role of all these uh materials they use? They simply use all these materials so as they can know the weight of their substances.

[00:06:34]That goes to physics and mathematics.

[00:06:38]Okay? You go to the shop um and you want to buy rice. They're going to measure this rice using a weighing scale to know its weight.

[00:06:46]The rice has a whole.

[00:06:48]That is for the case of physics and math.

[00:06:51]But here, in chemistry, the mole concept is going to give us the weight of our substances, but in bits.

[00:07:00]And for us, the concept that we use is known as mole concept.

[00:07:06]Hope you have picked something from that.

[00:07:09]So, that aside, let's go to our topic.

[00:07:13]So, under here, today we are going to speak of calculating We are going to speak of calculating uh molar mass.

[00:07:23]Yes. So, we are going to start with molar mass. So, that's the first thing that we should know.

[00:07:29]So, number one, we are going The key targets of our lesson, we are going to speak of calculating calculating calculating molar mass.

[00:07:46]So, those are going to be the key targets here.

[00:07:50]Those are going to be the key targets here. Calculating molar mass, then from that, we are going to look at uh we are going to simply look at um maybe calculating calculating of mass of a substance, calculating of mass of a substance from an equation.

[00:08:18]Okay?

[00:08:19]Calculating mass of a substance from an equation. So, these are going to be the two end rows that we are going to look at.

[00:08:27]Okay?

[00:08:29]Uh if all goes well. Number one, we are going to know how do we calculate molar mass? What is molar mass? Then from that, we shall know how to calculate mass of a substance from an equation.

[00:08:40]And this is always set in most papers.

[00:08:44]If you're going to look into your mock papers that have been set in the previous 2 years, at least there is mole concept and they're asking you, find the mass of this substance. Find the mass of uh ethanol. Find the mass of magnesium.

[00:09:02]Such questions.

[00:09:04]Okay? So, we're going to cover that up.

[00:09:08]So, first thing's first, let's start our with calculating of molar mass.

[00:09:13]Calculating of molar mass.

[00:09:16]But now, before we go there, we should have first have a hint.

[00:09:20]Yes, we are going to calculate molar mass, but what is molar mass?

[00:09:25]What is molar mass? So, that's the first thing we have to know.

[00:09:30]After that, then we can calculate.

[00:09:33]So, number one, you You say molar mass.

[00:09:38]Uh this is the mass This is the mass of 1 mole of 1 mole of a substance.

[00:09:50]This is the mass of 1 mole of a substance or compound.

[00:09:58]Now, for you to be able to understand the 1 mole of a substance I'm speaking about, you're going to know this uh very well or better when we start our lesson.

[00:10:08]But put that into your mind. This is the mass of 1 mole of a substance or a compound.

[00:10:16]Hope I'm clear with that.

[00:10:18]So from that, we are going to know what are the units.

[00:10:22]What are the standard units of this uh molar mass we are speaking about? So, the standard units or what we call the SI units, the SI units, standard units are grams. So the standard units of uh this molar mass are grams, implying that anywhere we are going to calculate molar mass, our answer that we are going to get, we have to put grams. But we're not going to write the whole word.

[00:10:53]You'll only put g. So this g will stand for the molar mass you're the grams of your molar mass you're speaking about.

[00:11:03]Hope that is clear.

[00:11:05]We have said molar mass, this is the mass of 1 mole.

[00:11:10]Let me try to change here. This is the mass of 1 mole of a substance or a compound.

[00:11:18]And we are saying the standard units that we use while measuring or calculating for molar mass, they are gra- grams. But these grams, we are going to write them just simply with a small g after calculating.

[00:11:37]Hope that is okay.

[00:11:39]So, let's start.

[00:11:41]Let's try to start.

[00:11:46]Let's try to start the calculation.

[00:11:49]Okay.

[00:11:53]So, we can say calculate the molar mass of the following.

[00:11:59]And now, in molar mass, they're going to be giving us compounds. So, here they give us a compound.

[00:12:05]Calculate the molar mass of carbon dioxide.

[00:12:10]Calculate the molar mass of carbon dioxide.

[00:12:18]Carbon di- oxide.

[00:12:21]So, in most cases, you should be knowing the chemical formulas of these compounds. If you don't know them, you're going to be tricked around, and you're going to fail.

[00:12:32]Okay? And that lesson of chemical formulas, I'll be making it with our premium scholars.

[00:12:39]Soon as you remind me.

[00:12:42]So, they tell us calculate the molar mass of carbon dioxide.

[00:12:48]Calculate the molar mass of carbon dioxide. So, the chemical formula of carbon dioxide is C O and a two.

[00:13:01]Hope I'm clear with that. It is C O and a two.

[00:13:05]So, they tell us calculate the molar mass of carbon dioxide. How do we calculate the molar mass?

[00:13:13]Now, number one, whenever they're going to tell you to calculate for molar mass, they are going to give you mass numbers in brackets.

[00:13:21]So, in such a question, they'll tell you into brackets, mhm.

[00:13:26]Uh sorry.

[00:13:28]Let me make it better. They say in two brackets, C is equal to 12.

[00:13:34]C is equal to 12.

[00:13:36]Then they tell you O is equal to 16.

[00:13:44]O is equal to 16. Now, these numbers that you see in brackets, they are not some foreign numbers.

[00:13:52]The numbers themselves are chemistry.

[00:13:54]Okay? Now, these numbers that you see in brackets, they are called mass numbers.

[00:14:02]They are called massy numbers.

[00:14:06]Or if you don't call them mass numbers, someone else can call them the atomic mass.

[00:14:14]Someone else can call them the atomic mass.

[00:14:20]Now, what is this atomic mass constituting of?

[00:14:24]So, the atomic mass, let me first complete here.

[00:14:30]This atomic mass I'm speaking about, or the mass number, it is simply the summation It is simply the summation of the number of protons and neutrons in the nucleus of an atom.

[00:14:48]It has protons and neutrons.

[00:14:52]Okay?

[00:14:53]In the nucleus of an atom.

[00:14:56]Now, how do we calculate formula mass? Number one, you should know the number of atoms of the element in the compound.

[00:15:08]Let me write that.

[00:15:10]Step one, before even we calculate, step one, um, you should know you should know the number You should know the number of atoms of the element in the compound. You should know the number of atoms of the element in the compound.

[00:15:46]Hope that is clear. Now, how do I know the number of atoms of the element in the compound? When you look at this compound given to us here, it is carbon dioxide.

[00:15:59]But it is made up of atoms of different elements.

[00:16:03]Number one atom that we have there is C.

[00:16:07]The atom of a an element and C is the atom of carbon.

[00:16:14]In the compound known as carbon dioxide, this whole compound is known as carbon dioxide, but we are having C, which is carbon. So, carbon is the atom of the element still known as carbon.

[00:16:29]Then, all that you're seeing here, it is the atom of the element known as oxygen. So, number one, you should know the number of atoms of the element in the compound. So, let's know the number of atoms here. We have said it is C O and a two.

[00:16:52]So, I want to know how many atoms do we have there.

[00:16:56]So, number one, we are going to say C C is standing for carbon. How many atoms do we have there of carbon?

[00:17:05]Mhm. Now, we'll always look at the right or on the right of our element.

[00:17:13]If this element does not have a number there. In chemistry, there is always an indivisible one. So, you consider there to be a one.

[00:17:26]Okay? Hope that is clear.

[00:17:28]So, when you look at the right of this C, it does not have a number anywhere here.

[00:17:35]That implies that there is an indivisible one.

[00:17:40]Implying that carbon is one.

[00:17:43]If you don't take it into that way, you can also see that we are only having one carbon in atom. It's only a C. There's no number on it.

[00:17:54]Okay? So, that's the second way you can also analyze. So, here we are having one atom of carbon.

[00:18:00]It is only C. No number is there. So, come here and say C is one.

[00:18:06]Okay? Then from there, you go to oxygen.

[00:18:09]Oxygen is here.

[00:18:11]When you look at oxygen, let's look on its right and we see on its right it is having a two. Implying that oxygen we are having two.

[00:18:23]So, that is step one. You analyze the number of atoms of the element in the compound.

[00:18:29]We are done with that.

[00:18:31]Let me go to step two.

[00:18:33]What do we do in step two?

[00:18:37]Now, step two, what will you do?

[00:18:42]Step two, what will you do?

[00:18:45]You are going to multiply multiply the number of the atom of the element or the number of the element or elements with the corresponding with the corresponding uh mass number given in Remember the mass number we spoke about, the mass number given in brackets.

[00:19:21]I spoke of the mass number earlier there. And I said for it it will always be given to you in the brackets.

[00:19:29]If the paper that you're going to do there is a mole concept, you will always even see these numbers outside on the paper before even you starting to join your paper. They will tell you where necessary C is equal to 12. Outside on the paper before you open it.

[00:19:45]Okay? So, step two, what do we do?

[00:19:48]We multiply multiply the number of the elements with a corresponding mass number given in brackets.

[00:20:00]So, here they told us that C is 12. Hope you can see that. O is 16. So, you're going to come here and say Mhm. Now, you're calculating formula mass.

[00:20:11]You'll say molar mass.

[00:20:13]You write your word.

[00:20:15]Molar mass.

[00:20:18]I don't prefer people who write initials, eh? You write MM. That's not good. You write a full word.

[00:20:24]So, you'll say molar mass molar mass molar mass is equal to Mhm.

[00:20:32]We are going to start with this carbon here. Hope you're seeing it.

[00:20:37]So, we first analyze the number of carbon that we have. Mhm. Carbon we have one. Mhm. Times the corresponding mass number given to us. So, the mass number they gave us of carbon was 12. So, you come here and say times 12.

[00:20:55]Close brackets.

[00:20:58]Plus, then you go now to the other one.

[00:21:01]You go to oxygen. Oxygen we have seen that there are two atoms. So, we'll say two atoms of oxygen times Mhm.

[00:21:12]What is the corresponding mass number?

[00:21:15]It is 16.

[00:21:17]Okay, so you come here and say 16.

[00:21:23]Now, from that, what you're going to do is simple.

[00:21:27]You're just going to do simple mathematics.

[00:21:31]Just press your calculator and get the answer. This is 12 plus a two times 16, it will give us 44.

[00:21:42]Okay, hope you're all pressing your colleagues very well. So, 44, but what did we say? We say that the standard units Come back here and see it. The SI units are in grams, but we shall represent it by a G. We said that in our statement here.

[00:21:59]So, you'll come here and say 44 grams.

[00:22:04]You can underline your answer if you want. 44 grams, and this is very correct.

[00:22:11]So, simply, that's how we calculate for molar mass.

[00:22:17]Hope everyone has understood that very well.

[00:22:21]Hope everyone has understood that very well.

[00:22:24]Let's go to another trial, then I'm going to leave you questions.

[00:22:28]Let's go to another trial, then I'll leave you questions.

[00:22:33]Well, the lesson might stand for about 1 hour. So, be stiff. We are still going on. We say that key targets, let me first remind you of key targets of this lesson.

[00:22:43]We are going to calculate for molar mass. Hope you see it here, the one I spoke about. Then, we also calculate for calculating mass of a substance from an equation.

[00:22:53]Those are the two things that we are going to look at.

[00:22:57]So, so far, we are about to complete our molar mass.

[00:23:01]That's our first example. Mhm. The second one, calculate for me the molar mass of water.

[00:23:10]But I'm going to do this with you. Maybe you haven't gotten very well.

[00:23:14]Then I will leave you the assignment.

[00:23:16]Those in the premium group will send me under a mark.

[00:23:20]Those that haven't joined the premium group, I don't know who will help you, but you have to enroll to join.

[00:23:28]So, what do we do here? We said our step one, this is water by the way.

[00:23:34]And I told you should be knowing the what?

[00:23:37]The chemical formulas. If you don't know, I'm going to give you that lesson.

[00:23:41]Premium scholars, eh?

[00:23:44]You remind me of that lesson.

[00:23:46]So, you have to first know the chemical formula.

[00:23:50]So, the chemical formula of water is H2O.

[00:23:53]H2O.

[00:23:56]So, we are going to calculate its see molar mass. Number one, what do we do?

[00:24:01]We are going to analyze the number of atoms here. So, hydrogen here, we are having how many hydrogens?

[00:24:08]Hope you can all see that I the hydrogens are two. These are two here.

[00:24:13]So, you say hydrogen, we are having two hydrogens.

[00:24:18]Then you go to oxygen. Oxygen, it is one as you are seeing it. There's no number on it.

[00:24:24]Implying that it is one.

[00:24:27]You come here and calculate your molar mass. You say molar mass is equal to hydrogen, they're how many?

[00:24:34]They are two.

[00:24:36]Okay.

[00:24:37]But now, what is the mass number of hydrogen? I said this will always be provided to you.

[00:24:44]So, let me change color.

[00:24:48]Let me change color.

[00:24:49]So, hydrogen has a mass number of one.

[00:24:56]Hydrogen has a mass number of one.

[00:24:59]And oxygen has a mass number of 16.

[00:25:05]That is it respectively. This one has a mass number of 16.

[00:25:11]So, what I'm going to do in our calculations, we shall say two times the corresponding mass number. That is our step two that we said here. You multiply by the corresponding number.

[00:25:26]Uh mass number of your element. So, here we shall say two times one.

[00:25:33]Mhm. One is the mass number. Two, it is the number of hydrogens we have.

[00:25:40]Plus, mhm, we look at the oxygen.

[00:25:43]Oxygen, we are having one atom.

[00:25:46]It is one. We have gotten it from here.

[00:25:49]But, what is the corresponding uh mass number? It is 16. So, you come here and say times 16.

[00:25:59]Okay?

[00:26:00]But, before I even proceed, uh you people, you scholars, you have not yet subscribed to our YouTube channel.

[00:26:09]I'm going to post this class, but endeavor you subscribe. We have We want to make a heat target of 1,000 subscribers.

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[00:26:35]You subscribe. You can like. Then also, you comment about something that maybe want me to speak about in the next lesson, or you can appreciate anything.

[00:26:46]So, here we shall come and say is equal to two times one, simple math. That is two. This is 16. 16 + 2 that is 18.

[00:26:55]So, it is 18, but we say the SI units are in grams.

[00:27:00]So, you put your grams there.

[00:27:02]You underline if you want.

[00:27:04]And that will be very correct.

[00:27:07]So, that is what we do when they ask you to calculate for molar mass.

[00:27:14]Going to give you assignment. Going to give you activity.

[00:27:19]Your activity.

[00:27:22]Those that are You might ask me, "How am I going How will my work be seen by you?" Or "How will you mark it?"

[00:27:29]I I mark it in the premium group where I have lessons from, eh?

[00:27:34]Yes.

[00:27:36]This is just a another free lessons for all of you, but I don't often do that.

[00:27:41]So, activity uh calculate calculate calculate cal- culate the molar mass of the following the molar mass of the following Calculate the molar mass of the following Calculate the molar mass of the following.

[00:28:15]following. Okay.

[00:28:17]I've done a mistake here. following Mhm. So, these are the following compounds I want you to calculate for.

[00:28:26]You finish getting the answers, you send me the answers. For those that haven't joined the group my number I presented it to you very well.

[00:28:36]You come you you be registered with me, you join. Don't get scared if you don't have the whole 35,000.

[00:28:44]Installments are also allowed.

[00:28:46]Okay? So, I want you to calculate for me the mass number of this compound.

[00:28:56]I even don't know its name.

[00:28:58]But to me, I want you to to calculate it for me. That is one.

[00:29:04]Two.

[00:29:06]I want you to calculate for me the mass number of this other compound.

[00:29:17]That one there.

[00:29:18]I think three are enough.

[00:29:21]Three are enough.

[00:29:23]Or you want more?

[00:29:25]I want you to calculate for me the mass number, sorry, the molar mass of this.

[00:29:34]Yes.

[00:29:36]Those will be enough. Those that will want more, you'll come to me. Whereby Na Na Na is equal to 23.

[00:29:50]Na is equal to 23. C C is equal to 12.

[00:29:58]is equal to 12.

[00:30:00]O is equal to 16.

[00:30:04]That is for the first one there.

[00:30:07]Then the second one here.

[00:30:11]The second one here.

[00:30:15]We have a nitrogen. Where N is equal to 32.

[00:30:22]Where N is equal to 32.

[00:30:25]H is equal to one.

[00:30:29]H is equal to one.

[00:30:31]Then here.

[00:30:34]Where Ca Ca is equal to 40.

[00:30:42]Comma.

[00:30:43]C or capital C is equal to 12 and O is equal to 16.

[00:30:54]O is equal to 16.

[00:30:57]So, you go and try out that.

[00:30:59]I'll be waiting for the responses. So, that is that as it or that has been about calculation of That has been about calculation of molar mass. Hope everyone has understood that lesson. You take some water.

[00:31:18]Take some water. The 30 minutes are gone.

[00:31:21]So, we're going to the next 30 minutes of the lesson.

[00:31:24]What is it going to be about?

[00:31:27]Calculating of mass of a substance from an equation.

[00:31:31]Calculating of mass of a substance from any equation. So, you prepare for that.

[00:31:39]You prepare for that.

[00:31:43]You prepare for that.

[00:31:44]Very well, then we start.

[00:31:47]Mhm.

[00:32:00]You prepare for that very well and we start.

[00:32:04]Okay. Hope you have taken some water.

[00:32:09]Let's start. The second lesson, the key targets, I remind you let's go back and we check. Uh someone might be saying I'm overtaking. Let's check and we see.

[00:32:19]We spoke of our targets here. Let me label it.

[00:32:23]We said the other one, number one, was calculating for calculating for molar mass. We are done.

[00:32:31]Anyone complaining about that? No, we are done with that.

[00:32:36]Then the other one we said calculating for mass of a substance from any equation. So, this is what we are going to And we say these questions for them they are set.

[00:32:49]Mhm.

[00:32:51]They are set.

[00:32:52]So, the importance of uh the molar mass for which it is being used, its knowledge is used to calculate for this.

[00:33:00]So, if you don't know molar mass, you can't calculate for this.

[00:33:05]If you don't know molar mass, you can't calculate for this.

[00:33:26]Well, so let's start to our second one, the one about calculating of mass of a substance.

[00:33:39]Calculating for mass of a substance. You do that assignment, then you will send to me and we see what to do.

[00:33:53]Uh still I will introduce to you the academy.

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[00:34:53]Yeah, it also past it has past chemistry and biology.

[00:34:57]Yeah, it is called the sub or the carb academy.

[00:35:02]carb academy. Those that want to join the premium group to have lessons with us, you're going to contact this number here.

[00:35:11]Then you get the educational support.

[00:35:14]Yes, since I'm not going to give out all the lessons to be free.

[00:35:19]I won't do that.

[00:35:21]Yes.

[00:35:22]Okay, so let's start.

[00:35:26]Let's start. So this is the sample question. One of the questions that these people like to bring.

[00:35:33]Mhm, this is a sample question that was gotten from some mock board.

[00:35:36]Then I decided to use it as an example here.

[00:35:40]So please, all of us let's put our eyes open our eyes, let our eyes be wide.

[00:35:50]Let our eyes be wide.

[00:35:54]Okay?

[00:35:57]So let's start.

[00:36:01]Let's start.

[00:36:05]What are they telling us?

[00:36:07]Mhm, they are saying limestone limestone is decomposed to produce calcium oxide.

[00:36:16]Limestone is decomposed to produce calcium oxide that reacts with impurities during extraction of metals.

[00:36:28]Okay? They are telling us this calcium oxide reacts with impurities during extraction of metals such as iron.

[00:36:37]During the extraction, people found out that uh people found out that every hour they use 25 g of limestone. Every an hour they use what?

[00:36:52]25 g of lime limestone to produce to produce calcium oxide.

[00:37:00]What are they saying further?

[00:37:02]They give us the equation CaCO3.

[00:37:06]This one is standing for cali- for limestone.

[00:37:09]This is the chemical formula for limestone.

[00:37:12]Calcium carbonate decomposes. Here it had to be an arrow.

[00:37:18]Decomposes to give us what?

[00:37:22]To give us calcium oxide and carbon dioxide.

[00:37:27]Now, this is how the questions will come. Hope you can see.

[00:37:32]Categorize the products formed. We are not here for that. We are here for mole concept.

[00:37:37]Uh determine the number of moles.

[00:37:40]Mhm, we are not here for that.

[00:37:42]We are majorly here for this. Determine the amount of calcium oxide produced.

[00:37:50]Now, the amount of calcium oxide produced is what we are calling the mass.

[00:37:57]It's what we are calling the the mass.

[00:38:01]This is what we are calling the the mass.

[00:38:05]The one that we are going to calculate for in this lesson. We want to know how do we calculate for it? How do we do it?

[00:38:13]Okay? So, don't be scared. Things are going to be easy.

[00:38:18]Things are going to be easy. I'm going to give you the steps that you should use.

[00:38:23]Yes.

[00:38:25]Such that in the coming 1 hour we are done with the lesson.

[00:38:28]So, what do we do whenever we see such a question? Number one, you should read very well your question. You read as you're interpreting. You read as you're interpreting. This will help to give you a glimpse of what you should answer in your question.

[00:38:46]Let's start. Let's start.

[00:38:49]So, what are we going to do? Step one.

[00:38:53]Step one.

[00:38:55]Uh I think let me write it up here. Step one.

[00:39:00]Step one.

[00:39:02]We are going to calculate for the molar mass. Are you seeing how molar mass is helping us? So, whenever you're given to calculate for mass of a substance, your step one, you're going to calculate for the molar mass of your reactant. Let's write it here.

[00:39:23]Molar mass of your reactant.

[00:39:26]Molar mass of reactant.

[00:39:31]Molar mass of reactant. Now, the question is, how do I know the reactant?

[00:39:41]How do I know the reactant? I don't want to join this lesson to include two concepts in one lesson, but allow me to use it just to explain for you.

[00:39:50]>> [snorts] >> Now, are you seeing this equation that they have given us? They have given us some equation here. This one here.

[00:39:58]They are saying Ca Ca Mhm.

[00:40:02]CO of which we have said CaCO3 is a chemical formula of limestone.

[00:40:11]Does what? It is in solid state.

[00:40:15]It is in solid state. what does it do?

[00:40:18]It decomposes.

[00:40:20]The decomposition is represented by the arrow.

[00:40:24]So, it decomposes to give us calcium oxide.

[00:40:29]And calcium oxide is a what? It's also a solid.

[00:40:32]It is represented by the S. S stands for solid state.

[00:40:37]Plus carbon dioxide. But the carbon dioxide here is what?

[00:40:41]CO2. The carbon dioxide here is a gas. How do you show it is a gas? You put a G.

[00:40:50]The G there shall represent that it is a gas. Those that don't know how to balance equations, haha, you should see me very fast. That lesson is also going to be covered in the premium group.

[00:41:03]Okay? So, if you don't know, don't miss out. Enroll to join us at a very faster time before your your final exam. That is your name.

[00:41:17]So, you are saying step one, you calculate for molar mass of the reactant.

[00:41:22]How do you know the reactant? Now, for the case of this equation, we are blessed that it only has one reactant.

[00:41:29]Hope you know that the ones that are at the back of the arrow, they are what we call the reactants.

[00:41:35]Reactants.

[00:41:37]And the ones that are always in front of the arrow, they are what we call the products.

[00:41:43]This side will be the reactants, then this side will be with products.

[00:41:49]Let me first write that for people.

[00:41:53]Mhm, don't want you to say anything. So, what we have here, they are the products.

[00:41:59]Now, you will meet some equations when here we are having two reactants. Just we are saved that here it is one.

[00:42:06]When even though they are two reactants, don't be confused. How do you know the reactant?

[00:42:12]We know that reactant simply by reading our scenario.

[00:42:17]The reactant in the scenario whose mass was given.

[00:42:22]It is the one that we are going to find for its molar mass here.

[00:42:27]And it is the reactant that we are going to take. I repeat, the reactant whose mass is given in the question, it is the one that we are going to calculate for its molar mass on step one.

[00:42:41]If you are to check this question here, they said during the extraction, people found out that every hour they used 25 g of limestone.

[00:42:53]That is a key.

[00:42:55]25 g of limestone. Hope you're seeing it. 25 g of limestone.

[00:43:04]Implying that they have given us the statement that I have said, the reactant whose mass is given in the question is the one that you'll find for its molar mass. So, they have given us the mass of the reactant which is calcium carbonate. Even though here there were two reactants, for example, if here was I'm just assuming, if here was um anything, anything. For example, magnesium. Let me say there was magnesium oxide.

[00:43:35]Okay?

[00:43:37]How was I going to know that this is the reactant I'm going to deal with? You are going to know that this is the reactant you're going to deal with by by seeing which mass of a substance have they given you in the question.

[00:43:51]Which mass of the reactant? So, in this question, they only spoke of limestone.

[00:43:56]Implying that even though there were two, you are going to neglect this, but you are going to take this. Why?

[00:44:04]It is the one whose mass has been given in the question. Which mass have they given us?

[00:44:12]The mass has been simply 25 g. So, let's start calculating. Step one, you calculate the molar mass of the reactant. And I'm just from teaching you how to calculate for molar mass.

[00:44:25]So, we shall say molar mass is equal to Mhm.

[00:44:29]And for your own good, hope you can see here that they gave us even the what?

[00:44:34]They gave us their mass numbers.

[00:44:37]Mhm.

[00:44:38]So, we are calculating for molar mass of calcium carbonate.

[00:44:43]Calcium carbonate.

[00:44:48]We want to know its molar mass.

[00:44:52]We want to know its molar mass.

[00:44:56]Mhm.

[00:44:58]So, we can see that we are having one calcium. So, we shall say one calcium times What is the mass number? It is 40.

[00:45:08]Here, I'm going to be fast since I'm just from teaching this.

[00:45:12]Mhm. Into brackets.

[00:45:15]Plus, we go to carbon. Carbon is here.

[00:45:17]It is also one.

[00:45:19]We say plus one.

[00:45:22]Plus one. Mhm. Times What is its corresponding mass number? Carbon is 12.

[00:45:29]Times 12.

[00:45:32]Okay. Into brackets. Plus oxygen. How many oxygens do we have? We look to the right. They are three.

[00:45:40]So, we say three. Times What is the corresponding mass number?

[00:45:45]It is here.

[00:45:46]It is 16.

[00:45:52]It is 16. You do simple mathematics.

[00:45:55]I don't know which answer does it give you here.

[00:46:00]You can write there in the messages that has I don't have a calculator here. Someone to type that. Which answer does it give us?

[00:46:11]Okay, someone is saying it gives us 100.

[00:46:14]Hope everyone is getting that. It gives us what? 100. But we said the SI units of molar mass in what? I mean grams.

[00:46:26]So that is done. Step one, we calculate for the molar mass of the reactant. What next? What next? Huh, master. I am not going to do chemistry. Chemistry is hard. Who tells you chemistry is hard?

[00:46:40]Chemistry is very easy.

[00:46:42]So step two, what do we do? Step two.

[00:46:46]Step two, what do we do on step two? So on step two, simply we calculate we calculate for the molar mass of the product.

[00:46:59]Molar mass of the product of the product.

[00:47:07]Molar mass of the product. That's what we do on step two.

[00:47:11]Mhm, let's see now. How will we do that?

[00:47:16]How will we do that? Okay.

[00:47:19]So when you look on the side of the products, we have two. We are seeing calcium oxide is here and we are having carbon dioxide.

[00:47:28]Over that two, which one am I going to calculate for its molar mass as step two is telling me? So this is how you know the product. Now, that product that is asked for you in the question to calculate for, to determine for, to look for, it is the one that you're going to find for its molar mass.

[00:47:54]If you go to this question here, number Roman numeral two I I They said determine the amount of calcium oxide.

[00:48:07]So this one has given us the product that we are going to deal with. Yes, they are two. We have calcium oxide and carbon dioxide. How do we know the product exactly?

[00:48:19]It is that product that is given to you that is asked for you to calculate for that you will calculate for its molar mass. Hope that is not confusing.

[00:48:31]So here they told us determine the amount of calcium oxide. So we shall calculate for calcium oxide.

[00:48:38]Of which it is C A C A and O.

[00:48:44]As you seeing it from the equation here.

[00:48:48]How do you calculate for that? We shall say C A O is equal to Mhm. How many calciums? They are one.

[00:48:55]What is our corresponding mass number?

[00:48:58]It is 40.

[00:49:00]Into brackets into brackets plus into brackets plus Mhm.

[00:49:09]Plus Mhm. Oxygen it is also one. You can see that.

[00:49:14]What is our corresponding mass number in brackets? It is 16.

[00:49:20]You You close your brackets.

[00:49:23]Mhm.

[00:49:25]Simple mathematics, people.

[00:49:28]Simple mathematics. 40 + 16 right from the answer.

[00:49:34]Someone is saying 56.

[00:49:37]Hope you're giving me correct things.

[00:49:40]Yeah, some of you I don't trust your calculations.

[00:49:43]But I trust this one.

[00:49:46]It is 56.

[00:49:51]That is step That is step what?

[00:49:56]That is simply step two.

[00:49:59]Are you seeing how you're getting your marks? So far I have two marks.

[00:50:03]We proceed. This question has about five marks.

[00:50:06]What am I going to do on step three?

[00:50:11]What am I going to do on step three? I think step three Let me write it above here.

[00:50:18]Okay, let me write it down.

[00:50:21]Step three.

[00:50:25]Step three. What do we do? Now, on step three, you're going to recopy your equation.

[00:50:33]Step three.

[00:50:35]Recopy You recopy your equation.

[00:50:40]Recopy the equation Recopy the equation from the question.

[00:50:50]From the question or from the item.

[00:50:53]Let's call it like that.

[00:50:56]So, you're just going to transfer the equation they gave you here, you bring it onto paper down.

[00:51:02]Simple like that.

[00:51:04]So, you're going to come here and write the equation. It is Mhm, 2 Ca Ca Okay.

[00:51:14]C3 Is it C3? CO under three.

[00:51:23]It is a solid. I will not write that.

[00:51:25]Not waste time. But, you do that.

[00:51:29]It is a solid. Then, here the products we have Ca O which is also a solid plus carbon dioxide which is CO2.

[00:51:42]Now, after you're recopying your equation, what are you going to do?

[00:51:46]You are going to look for the reactant.

[00:51:49]I repeat. You are going to look for the reactant whose mass was given in the question.

[00:51:55]You put two ticks above it and write that mass that they gave you. I repeat. You are going to look for the reactant whose mass was given to you in the question. You put two ticks above it and write that mass.

[00:52:12]And we already identified the reactant.

[00:52:15]It was limestone and they gave us its C mass. It was 25.

[00:52:20]So, we're going to come here above, slightly above, you put two ticks and write the mass they gave you. It was what? 25.

[00:52:30]25 g.

[00:52:34]Only that.

[00:52:36]You'll see how it is going to help you.

[00:52:37]Let's proceed.

[00:52:40]From that, you on still step three, you're going to analyze the number of moles that you have.

[00:52:47]Okay?

[00:52:48]You're going to analyze the number of your the number of moles of your reactant and the number of moles of your products. Already we know them.

[00:52:56]How do you know the number of moles? You look on the left of the whole compound.

[00:53:00]This is the left here.

[00:53:02]Here is the left.

[00:53:05]And there is no number, implying that there is one mole. Always when you have no number there, there's always an indivisible one.

[00:53:14]So, here we have one mole.

[00:53:16]Okay? But if there was a three here, then it was going to become three moles.

[00:53:23]Hope I'm clear. But since there's no number, there's an indivisible one.

[00:53:29]Mhm, that is for the reactant. Let's go to the product, same to the product. I'm not seeing anything here on its whole left.

[00:53:36]Implying that here I also have one mole.

[00:53:41]We also have one here.

[00:53:44]Now, we are going to calculate. We are starting.

[00:53:48]Now, this number of moles that you have written, they are going to help you to write the statement. How are they going to help you to write the statement? You will say, mhm, one mole Are you seeing here this? Mhm, you'll come here and say one mole one mole of what?

[00:54:09]of of, mhm, you start from here. One mole of, mhm, what is this?

[00:54:19]calcium oxide, mhm, did what?

[00:54:25]That arrow means it produced Okay, you say one mole of calcium oxide, sorry, calcium carbonate, it produced produced what?

[00:54:38]You do the same the other side.

[00:54:40]What did it produce? You do the same thing.

[00:54:44]produced, mhm, you say one mole of carbon dioxide.

[00:54:52]It produced one mole one mole of what? of carbon di- oxide.

[00:55:07]That is how it is helping you. That is first thing. Now, we are concluding to our answer.

[00:55:13]From that, you're going now to That person writing on my screen.

[00:55:20]Mhm, now from that, you're going now to fulfill or you're going to fill the molar mass that you got into the space here. So, the number of moles that are here, you're going to multiply them by the molar mass that you calculated earlier. So, you'll come down and say one times mhm What is the molar mass of calcium carbonate we calculated for? It is here.

[00:55:47]100 g.

[00:55:49]So, you'll come here and say 1 * 100 100 g.

[00:55:58]1 * 100 g of what?

[00:56:01]Of what?

[00:56:03]Of calcium carbonate.

[00:56:06]Hope everyone is seeing where it is coming from.

[00:56:09]Produced And now, never use arrows. Write statements. You use arrows even though the answer is correct, we shall cross that.

[00:56:19]Mhm, produced what?

[00:56:22]Produced You do the same thing the other side.

[00:56:26]You say one times mhm What is the molar mass of carbon dioxide we calculated for?

[00:56:34]It is here. 56 Produced 1 * 56 g.

[00:56:41]1 * 56 g of carbon dioxide.

[00:56:51]Okay? Hope you are still together.

[00:56:53]Now, you make yourself remember What about the mass that I ticked?

[00:56:59]There's some mass that I labeled above calcium carbonate. What about the 25?

[00:57:06]So, remember this 25 that is here. So, you'll come down and say, "What about 25?"

[00:57:12]g Hope you're seeing where it is coming from. I'm moving in steps and very slowly for everyone to understand.

[00:57:20]What about 25 g of calcium carbonate?

[00:57:23]So, you say 25 g of calcium carbonate These ones will produce mhm.

[00:57:31]Now, this is current since we don't know. So you say this one is produced you cross multiply.

[00:57:39]How do we cross multiply in chemistry?

[00:57:41]Open your eyes.

[00:57:45]You say 56 56 which is on your right. Hope you can see this 56 on your right.

[00:57:55]Mhm. That is 1 * 56. Mhm.

[00:57:58]times 25 which is on your left but below left.

[00:58:08]Hope everyone is seeing.

[00:58:09]divide by 100 which is on your left but upper left here.

[00:58:20]Okay.

[00:58:21]into brackets We are going to get grams of carbon di- over carbon dioxide.

[00:58:33]Oh, someone didn't tell me. It is it was uh calcium oxide. You people you didn't remind me.

[00:58:41]But still it is the same thing.

[00:58:44]Also here we had one mole of calcium oxide. It's what they asked us to calculate for not carbon dioxide.

[00:58:52]So it's one mole here over It is not for carbon dioxide.

[00:58:59]It they had asked us to calculate. Check the question. The amount of calcium oxide.

[00:59:05]Sorry for that. And you didn't remind me.

[00:59:08]So we change this. It is calcium oxide. We cross this once.

[00:59:15]And you say it's for calcium oxide.

[00:59:20]Same here. Calcium oxide. Sorry for that.

[00:59:26]And even you can see the molar mass we calculated for our product was calcium oxide.

[00:59:32]Mhm. So, you do simple math and get the answer there.

[00:59:37]You do simple math and get the answer there. It will be 56 * 25 / 100.

[00:59:47]People with calculators, tell me the answer.

[00:59:50]Okay.

[00:59:52]Someone has said 14.

[00:59:54]14 g of calcium carbonate.

[01:00:01]Calcium oxide, not carbonate.

[01:00:08]The problem time is gone. I also want to sleep, eh.

[01:00:11]That's why I'm making slips.

[01:00:14]Yeah, but that is human.

[01:00:16]So, that is the answer.

[01:00:19]14 g of calcium carbonate.

[01:00:23]Hope everyone has moved with me very well. You have learned how we do these things. So, whenever I ask you to calculate for mass of any substance, those are the steps you will follow.

[01:00:33]I gave you the step one, it is there.

[01:00:36]So, this will be will earn you a mark.

[01:00:38]That is correct. Mhm.

[01:00:42]Mhm.

[01:00:43]This will also earn you a mark.

[01:00:46]Mhm. This formula here, the equation will earn you a mark. This will earn you a mark, and your answer will also earn you a mark. So, this one is always marked between five to six marks.

[01:00:59]Ah, and why don't you pass your chemistry?

[01:01:02]Five to six, see? Marks.

[01:01:08]So, that is how to go.

[01:01:11]So, for those that have maybe uh not picked the something well, you please go to YouTube. I'll post this lesson.

[01:01:20]And to YouTube, you first you subscribe to that channel, then you watch.

[01:01:24]Subscribe, you like the lesson, and you watch. If you have any other inquiry, you comment.

[01:01:32]Well, that's the end of our lesson. I remain Mr. Henry.

[01:01:37]Mr. Henry.

[01:01:39]A tutor of Pass Chemistry Uganda, that can be found on any web on any social media platform.

[01:01:48]What do we do? Coming from Pass Chemistry or what we call Carb Academy.

[01:01:56]Carb Academy.

[01:01:58]Thanks for being on the channel.

[01:02:00]How do you join the premium group? I said joining the premium group is 35,000, and it is working for the whole term.

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[01:02:34]So, these were the key targets of our lesson, and we have completed them. So, you can take screenshots. And take And I want my my homework. I left this homework here.

[01:02:45]I want it.

[01:02:47]So, you take screenshots and uh we'll see next time. This has been a free lesson. Thanks for