2025 GCE Science Paper 2 Fully Revised l Mole Concept l Metals l Periodic Tables, Organic Chemistryl

[00:00:01]Okay, good morning everyone.

[00:00:04]I welcome you to this wonderful session.

[00:00:07]And of course today we shall be doing uh science paper two.

[00:00:10]Now, let me make this emphasis.

[00:00:13]I will make sure that I simplify your mole concept, your metals, and also other topics that are really so important like the periodic table. Most of you really struggle a lot, especially with mole concept.

[00:00:27]And mole concept doesn't miss. But I'm going to show you the tricks that you'll be using whenever you want to solve a question under mole concept. And also concepts on periodic table, you need to understand them. Not only the periodic table, also metals and things like organic chemistry, which I will be able to highlight to you.

[00:00:48]Now, I will be posting videos almost every day. So, make sure that you subscribe to this YouTube channel. Subscribe to this YouTube channel right now. Follow this YouTube channel and you access all the lessons that I post on this particular channel. And of course, if you want personal tuitions, make sure you inbox on this WhatsApp number, which I'll show on the screen, which is plus 26 077 66 40 46. And then I'll be able to respond to you.

[00:01:25]And then you can ask me questions concerning anything that you want. Okay?

[00:01:30]Now, let me proceed with answering this particular paper.

[00:01:38]Travel with me.

[00:01:40]Let's get started. We'll start with the MCQs or the multiple choice questions.

[00:01:45]You are given particularly 20 multiple choice questions, which I'll be able to explain each one of them, how the answer will be coming about.

[00:01:55]The first question is saying Elena accidentally sucks into the mouth a solution of sodium hydroxide during titration.

[00:02:05]Choose the appropriate action Elena should take.

[00:02:09]Now, sodium hydroxide is a basic medium.

[00:02:14]Okay? Sodium hydroxide is a basic medium.

[00:02:17]It has no uh acidic content in it. It's a basic medium. That implies that even if it gets into your mouth or into your stomach, it will have no effect on you.

[00:02:30]And that is the reason as to why your answer is going to be D. Spit out the solution and thoroughly rinse the mouth with water. Water is basic. Uh sodium hydroxide is also basic. No effect. So, your best answer is going to be uh D.

[00:02:52]Next.

[00:02:55]Which states of matter exists at the boiling point of a substance?

[00:03:01]So, a substance is boiling.

[00:03:04]When a substance is boiling, it is a liquid. At the same time, it is in its gaseous state. Then, once it boils, it becomes a gas. So, boiling is a state of liquid as well as gas.

[00:03:20]Okay? And that is why your answer is going to be C. Okay?

[00:03:27]Question three.

[00:03:28]The diagram shows changes of states among the three states of matter.

[00:03:34]Okay? As you are able to see on this particular uh uh diagram that they've showed you, they've showed you different states of matter.

[00:03:43]Then, the question is saying, "Why are these changes called physical changes rather than chemical changes?" So, a physical change is something that you cannot change. You cannot alter it with it. Okay? It can't be changed in any way. It remains the same way it is. A chemical change is something that you can easily change. Okay? Or it is something that can produce new substances. That's what I mean. Okay?

[00:04:11]When I say change. In other words, two molecules can react to produce a new uh product. But for physical changes, you are reacting two molecules that cannot significantly produce any other molecule. Okay? So, no changes can actually be made with physical, but changes can actually be made with chemical. Okay? So, the best answer is because they produce no new substances.

[00:04:40]They can't be changed. So, the best answer is D.

[00:04:44]Uh D.

[00:04:49]Which of the following is the best method used to separate sugar crystals from sugar solution during the production of uh sugar? Now, you have sugar crystals.

[00:05:04]At the same time, you have sugar solution. Whenever you hear crystallization, you are you are separating two solids.

[00:05:13]One is a crystal, one is dissolving in a solution. You are going to use crystallization.

[00:05:26]Next.

[00:05:27]Elena accidentally mixed iodine crystals with magnesium chloride.

[00:05:33]Which method would be suitable to separate this mixture? Now, this is iodine crystals with magnesium Magnesium chloride is a is a salt. Okay?

[00:05:45]So, you have got crystals as well as the a salt.

[00:05:51]So, the best way is simply to heat Okay? To heat the the substance, one is going to vaporize, the other one is going to remain and eventually form crystals. And that is why you are going to go with the D, which is simply sublimation.

[00:06:15]Which of the following is the approximate mass atomic unit for electrons? It is simply 1 over 1840.

[00:06:24]Okay? 1 over 1840. Okay? So, make sure you take note of that. I'm sure even when you check on the periodic table just underneath there on the corner, you would be able to see a 1 over 1840. So, the best answer is actually B.

[00:06:45]Okay? You use the 1 over 1840 to also define uh isotopes.

[00:06:50]The following diagram shows the structure of an atom for element W.

[00:06:55]So, this is element W. Choose the chemical formula of the compound formed when W reacts with the oxygen. Okay?

[00:07:04]When W reacts with the oxygen. So, oxygen When you check properly, check you will notice that a W this W uh molecule it has one electron in its outermost shell, meaning it has a valence of one.

[00:07:24]So, W has a valence of who? One.

[00:07:30]Right?

[00:07:32]Then, oxygen has a valence of two minus.

[00:07:37]This is what I originally So, this one will come this side, this one will come this side.

[00:07:43]W is going to be W2 then oxygen.

[00:07:48]This is how your formed molecule is going to look like.

[00:07:52]And that makes our answer to become C.

[00:07:56]Okay, so this one was actually very simple. You just needed to show this particular uh how a a a a a a molecule is actually formed. Okay?

[00:08:13]Hydrochloric acid is used to clean some metals. The acid reacts with oxide layer on the surface of the metal. Which of the following are the products? So, we've got an acid which is reacting with the an oxide layer. Okay?

[00:08:36]Which is reacting with the an oxide layer.

[00:08:43]An oxide layer of a metal. So, when acids react with a metal, what do they produce?

[00:08:50]There are two things they produce.

[00:08:52]The first one is called a salt.

[00:08:55]The second one is called water.

[00:08:58]When an acid reacts with a metal, two things are produced. One should be a salt, the other one should be water.

[00:09:09]Okay, so number eight is simply D.

[00:09:12]Please take note. Acid plus metal is equal to salt plus water.

[00:09:21]Let's go to question nine.

[00:09:25]Question nine is simply stating the results of three tests carried out on a solution of compound M are shown in the table.

[00:09:34]Then they say this is aqua sodium hydroxide. When added, it produced a white uh PPT formed soluble in excess. Then aqueous ammonia added, it produced a white uh precipitate which was formed uh soluble in excess.

[00:09:52]Then when aqueous hydrochloric acid was added, a fluorescence of a gas that turns lime water milky observed. Now, all this is not important. This you won't be able to get the answer from this description. The answer is here.

[00:10:08]A fluorescence of a gas that turns what?

[00:10:11]Lime water.

[00:10:14]Milky was observed. So, it's a carbonate. A carbonate is the one that turns uh lime water milky. So, this one should come out.

[00:10:26]This one should do come out. Okay? Now, they're saying hydrochloric uh aqueous hydrochloric acid was added, a first a fluorescence of a gas that turns lime water milky was observed.

[00:10:39]Okay?

[00:10:41]And then they say aqueous ammonia was added, a white precipitate was formed and it was soluble in uh excess.

[00:10:49]So, aluminum in excess not soluble. The one which is soluble is actually zinc carbonate.

[00:10:57]Okay?

[00:10:58]Zinc carbonate.

[00:11:01]Aluminum is usually not soluble because it is very unreactive. And what makes it unreactive is because it easily combats with oxygen when left in air, in free air. It combats with oxygen making it very unlikely to react with anything.

[00:11:18]So, it is less likely to be soluble. But for zinc, zinc is very much soluble.

[00:11:26]Okay?

[00:11:27]Very much soluble especially in uh substances like ammonia, okay?

[00:11:38]We have this question.

[00:11:40]2.4 g of magnesium ribbon was a uh reacted with the 100 cm³ of two uh molar dilute sulfuric acid. What is the volume of the gas which was produced at the room temperature and the pressure?

[00:11:56]So, the first thing that you need to know is they've they've said 2.4 g of magnesium ribbon was reacted with the sulfuric acid. So, the first thing you need to do is simply to be able to generate an equation. So, if we wanted to generate an equation, we're reacting magnesium. Let's try to do this.

[00:12:15]So, magnesium is reacting with uh sulfuric acid.

[00:12:22]What is being produced is going to be magnesium sulfate.

[00:12:26]Okay?

[00:12:30]Magnesium sulfate, we all know how to write magnesium sulfate. The two on magnesium and the two on the sulfate will cancel each other.

[00:12:38]And then what you're going to produce is simply hydrogen gas, okay?

[00:12:44]And it is actually this gas that is escaping. The hydrogen gas is the one that we are looking for. It is actually the gas that is escaping.

[00:12:55]Now, what exactly do we have?

[00:12:58]We have been told that 2.4 g of magnesium ribbon was reacted with the 100 uh cubic centimeters of two molar dilute sulfuric acid. So, we can find the number of moles of sulfuric acid.

[00:13:14]Okay? We need to find the number of moles of sulfuric acid. But before we do that, remember that this is not in decimeters, so we need to change it. So, we can say 100 over 1,000.

[00:13:28]Let's see. 100 over 1,000.

[00:13:34]You change it into cubic decimeters, you're going to have 0.1 decimeters.

[00:13:42]Okay? 0.1 uh uh cubic decimeters.

[00:13:49]Now, after you have your 0.1 cubic decimeters, let's try to see if at all you can find the number of moles.

[00:13:59]So, number of moles for this particular acid, Okay, so you can see the number of moles is going to equal to Okay.

[00:14:14]I might confuse you if I go directly.

[00:14:16]So, concentration or the molar concentration is equal to the number of moles over the volume. You cross multiply the number of moles is equal to So, what we have is a two there.

[00:14:29]Two multiplied by 0.1 Number of moles is equal to So, 0.1 multiplied by two we're getting a 0.2.

[00:14:44]Now, we have found the number of moles of the this particular uh uh acid.

[00:14:52]Right?

[00:14:53]Which happens to be your 0.2.

[00:14:58]Now, after having found 0.2, we can now find we can now try to find the moles of um We can use the mole to mole ratio to simply find the the osses the volume of this particular guy here.

[00:15:18]Okay? So, you're going to get your magnesium.

[00:15:21]Try to compare with uh your So, you try to compare it with your gas which was produced because that's the one it is relating to. So, you will compare it with your gas.

[00:15:37]Now, we have found the number of moles of this uh particular acid.

[00:15:42]Which other number of moles should we find that can help us? Let's try to find for magnesium also. It's very important.

[00:15:48]That's why we're given this mass.

[00:15:51]Now, we know that magnesium the mister of magnesium on the periodic table Okay, let's check it out.

[00:16:02]The mister of magnesium on the periodic table is simply 24.

[00:16:09]So, 24 is the mister of magnesium.

[00:16:13]Then, we say number of moles is equal to the mass over the mister.

[00:16:20]So, number of moles is equal to what is the mass? It is 2.4 over 24. So, the number of moles are going to have is 0.1. So, you're going to get your 0.1 moles of magnesium. You put them there. Okay, so these are are the ones which are going to help us.

[00:16:36]Okay, let's forget about this first.

[00:16:38]>> [snorts] >> Then, 0.1, we are going to compare it because it's a mole to mole ratio.

[00:16:44]So, let's check.

[00:16:46]First of all, let's check mole to mole ratio.

[00:16:51]So, because it's a mole to mole ratio of 1 to 1 because we have one mole. There's only one mole here of magnesium. Let's check. Also, one mole of here of uh hydrogen. So, even here there's one mole of hydrogen. That implies uh the 0.1 mole of magnesium is the same one for hydrogen here. Or, if you want you can calculate. You just put X here then you cross multiply.

[00:17:17]So, X is going to equal to 0.1. Have you seen?

[00:17:22]So, this 0.1 is the number of moles of this acid.

[00:17:26]Okay, so this this this gas is hydrogen.

[00:17:29]Now, remember they are saying at room temperature and pressure.

[00:17:33]So, at room temperature and pressure, 1 mole of any gas is equal to 24 cubic decimeter.

[00:17:41]Okay?

[00:17:43]Then, how about 0.1 of hydrogen? How is it going to be? We put X and we cross multiply.

[00:17:53]So, 0.1 multiplied by 24, we are getting 2.4 cubic decimeter.

[00:18:03]Okay, so where is our answer? The answer is going to be B.

[00:18:07]So, basically here, all you have to do is create a balanced chemical equation.

[00:18:14]When you create that balanced chemical equation, compare using mole to mole ratio.

[00:18:20]Okay? Get your magnesium, compare it with your hydrogen.

[00:18:25]You have 1 mole of magnesium.

[00:18:27]There you have 1 mole of hydrogen. Find the number of moles of magnesium.

[00:18:34]Put an X here. Cross multiply.

[00:18:37]Find the X, which are going to be the number of moles of hydrogen.

[00:18:41]Then from there, because it's at RTP, make sure you multiply by 24. Whatever you get is your answer.

[00:18:48]Okay?

[00:18:51]We come to the next question.

[00:18:53]Calcium carbonate thermally decomposes to form calcium oxide and carbon dioxide according to the equation uh given.

[00:19:02]Then they say 8.0 g of calcium carbonate was strongly heated in a crucible and 3.4 g of calcium oxide remained in the crucible. What was the percentage yield?

[00:19:14]Now, percentage yield is actually very simple to calculate. It's just the actual yield over theoretical yield. So, we can say percentage yield is equal to actual over theoretical multiplied by 100. Now, let me show you how simple it is.

[00:19:37]Get your the same thing that I did on top. Get your balanced equation.

[00:19:43]So, this is our balanced equation.

[00:19:46]Now, they are saying what was the percentage yield of calcium oxide? So, they want us to calculate the percentage yield of this guy.

[00:19:56]So, get what was it decomposing? So, it was calcium carbonate.

[00:20:02]Compare it with what is being produced, which is calcium oxide.

[00:20:07]Right?

[00:20:08]Find the mister of calcium carbonate. We know it is 100.

[00:20:14]Find the mister of calcium oxide. So, the mister of calcium oxide, how do you find it?

[00:20:23]So, it's going to be 1 multiplied by What is calcium? Calcium is 40.

[00:20:29]Then, oxygen it will be 1 multiplied by 16.

[00:20:34]So, from there I'll say 40 + 16 56.

[00:20:40]grams per mole 56 So, this is going to be 56. Of course, this is going to be gram per mole.

[00:20:49]Even here we're going to have 56.

[00:20:52]gram per mole. Just find the mister.

[00:20:54]Okay? Find the mister of calcium carbonate and the mister of calcium oxide. Then, from there what do we do?

[00:21:00]Simple. Just get your 8 g, which was given for calcium carbonate.

[00:21:07]Put it here.

[00:21:08]Then, this side put X, the same thing that I did. You see how simple it is? So from there you cross multiply.

[00:21:14]Then you're going to have the 100 this side. So 100 X is equal to Then we're going to say 56 multiplied by eight.

[00:21:24]Then you find four uh 448.

[00:21:29]Then you divide by 100, even this side by 100. You'll see what will happen.

[00:21:35]So if you divide by 100, you're going to get something like 4.8 uh sorry.

[00:21:45]4.48 Okay? grams Okay? 4.48 grams. Now, this 4.8 that you have calculated is what we are calling as your theoretical because you theoretically calculated it.

[00:22:04]Now we can solve. So you watch you watch you watch me you watch compare in question you will become a moon. Okay?

[00:22:12]You will become a moon.

[00:22:13]So you get your 3.4 over then you are going to divide it by that value which you calculated like this. Then you multiply by 100.

[00:22:28]That's how simple it is. So three just get your 3.4 divided by 4.48 then multiply by 100.

[00:22:38]You're getting 75.89, which you can round off to 76 percent.

[00:22:46]Okay? And that's how they found the answer to be A.

[00:22:54]Hydrogen peroxide solution decomposes very slowly at room temperature to produce oxygen and water. Apart from increasing the temperature, suggest the best way the reaction can be speeded up. Okay, so apart from increasing the temperature, the best way to increase uh a reaction is simply by using a suitable catalyst. Just use a catalyst, you speed up the rate of reaction. Of course, the answer is going to be D.

[00:23:24]The diagram shows the electronic structure of an ion of element L. To which group and period of the periodic table does element L belong to?

[00:23:37]Now, guys, I want you to look at this. I want you to follow me well.

[00:23:40]Now, now now you want to look at that.

[00:23:43]You have seen what is inside here.

[00:23:45]These are electrons in their in their shells.

[00:23:50]Now, here they are telling you that this is three plus, which tells you that this element had three extra electrons in its outermost shell.

[00:24:03]In other words, at first, before they did anything, you actually saw it.

[00:24:07]Okay, it was like this. I want you to see.

[00:24:10]You can just saw.

[00:24:12]Okay?

[00:24:14]This is how it was at first.

[00:24:21]They just wanted to confuse you.

[00:24:23]Okay?

[00:24:25]Then the last one contained three electrons.

[00:24:29]Okay? Now, these three electrons, because it's uh uh uh it's it's supposed to lose the three electrons to become balanced, that is why they are saying it's three plus, because it is losing.

[00:24:42]Now, I want you to look at this. Because it has got a valency of three plus, the valency is what determines the group. So, it is going to be in a group three.

[00:24:56]Now, this is what I wanted to to see the concept because it has got three shells.

[00:25:02]The first shell, the second shell, and the third shell which you could not see.

[00:25:07]It is going to be in period three.

[00:25:09]Three.

[00:25:15]Simple.

[00:25:16]So, group three, period three is B.

[00:25:18]That's how they you found you found B.

[00:25:22]Okay, if you found that question.

[00:25:24]Let's enjoy these questions, guys.

[00:25:26]Which is the electronic configuration of a noble gas used to provide an inert atmosphere in welding?

[00:25:34]Okay, electronic configuration of an inert gas which is used in welding.

[00:25:40]Okay, so of course welding, we know that we use argon.

[00:25:44]So, let's check where is argon? Argon is by the group eight of the periodic table.

[00:25:52]Okay, so of course argon is [clears throat] written like this. Let me show you.

[00:26:03]Argon is written like this.

[00:26:05]On top, it has 40. Down here it has 18.

[00:26:08]You are using this to write your electronic configuration.

[00:26:12]So, because it has 18, the first shell is going to hold two. The second shell is going to hold eight which make it 10. The second shell can hold eight which make it uh uh which make it 18. So, this is 8 + 8 16 + 2 it is 18. And this is the 18 we're getting. So, this is going to be the electronic configuration.

[00:26:37]Okay.

[00:26:42]Metal Y was added to iron sulfate solution and the solution changed from green to colorless.

[00:26:50]What is the identity of metal Y? So, I want to I want you to to to really get uh something.

[00:27:01]You have a metal Y which was added to iron two sulfate solution and the solution changed from green to colorless. So, this is under metals. You will need to know the properties of all metals. Which one turns pink, which one turns green, which one turns what, whichever color, which one turns colorless, especially more colorless, especially more of aluminum. But when you say green, you know, green, pink, for pink, copper of course, green, zinc, magnesium can. Okay? So, the answer is going to be A, magnesium.

[00:27:35]Copper don't uh line it up with this particular property.

[00:27:40]Okay?

[00:27:44]So, magnesium. Magnesium, zinc, those two elements, they usually present with that particular though.

[00:27:51]Zinc sometimes brown, copper pink.

[00:27:55]Yeah, like that. Okay? So, magnesium of course is your answer.

[00:28:05]16. The diagram shows the main stages in the manufacture of an ammonia-based fertilizer. We have got nitrogen. Of course, this is Haber process. Use nitrogen, this is hydrogen. What is happening in the process labeled Y?

[00:28:21]Okay?

[00:28:23]So, of course, the answer is simply D because you have untreated hydrogen and nitrogen which are just being uh recycled. Okay?

[00:28:34]>> [sighs] >> Here.

[00:28:42]17. Methane is reacted with steam in the presence of nickel as a catalyst to produce a gas and carbon dioxide.

[00:28:52]Okay, then they say, "What is the suitable method of collection for gas T and the reason?"

[00:28:59]Okay, so of course, it's going to be uh upward delivery and then the gas should be less dense than air.

[00:29:07]>> [clears throat] >> Okay, upward delivery, gas should be less dense than air.

[00:29:13]Which one is that? Okay, B.

[00:29:24]18, "Four different gases are released by the bacterial decay of vegetable matter. Which gas is mainly sourced from decay of vegetable matter?"

[00:29:37]Can you try out this one?

[00:29:39]Okay, perfect. You got it correct. It's actually methane.

[00:29:45]Which also happens to be uh natural gas.

[00:29:49]Of course, methane.

[00:29:54]Butane can undergo an addition reaction with steam to form compound R.

[00:30:01]What is the name of compound R? So, you are reacting an alk- an an alkene.

[00:30:07]You're reacting an alkene with water.

[00:30:16]Precisely, you should know that you're going to produce an alcohol.

[00:30:22]So, this one is butane plus water, you're going to produce butanol.

[00:30:29]Which is an alcohol.

[00:30:35]Polymers are made using monomers.

[00:30:39]The following are structures of some monomers. We've got W, we've got X, we've got Y, we've got Z.

[00:30:46]Identify the correct set of monomers that form a polyamide linkage. So, a polyamide linkage contains an amide functional group.

[00:31:02]So, we're going to have an amide functional group and a carboxylic acid functional group.

[00:31:15]So, an amide functional group is going to look like this.

[00:31:20]A carboxylic acid functional group will look like this.

[00:31:24]Or Sorry, supposed to be OH here.

[00:31:30]Uh let me put the O this side.

[00:31:33]Like this.

[00:31:36]So, this one should be there and also an at least a carboxylic acid. So, this This there's no carboxylic acid, no carboxylic acid.

[00:31:48]Okay?

[00:31:51]Here at least there's a double bond.

[00:31:53]Here there was no double bond.

[00:31:56]Okay, so this one is going to be Let me see.

[00:31:59]This one suits perfect.

[00:32:01]So, it's going to be Y and Z.

[00:32:05]Okay?

[00:32:06]That's how I would solve it. Okay?

[00:32:08]That's how I would find my answer.

[00:32:11]Accordingly to me.

[00:32:13]But actually that's the correct answer.

[00:32:18]Let's try out section B.

[00:32:22]Now, this section is actually very interesting because most of the topics that you underlined actually come.

[00:32:30]The first question was actually stating there are various challenges caused by chemical industry activities.

[00:32:38]State one challenge caused by chemical industrial activities on the land. So, chemical industrial activities, you're throwing waste, you're throwing rubbish on the land. What happens? Land pollution.

[00:32:50]Okay?

[00:32:53]Land pollution. Land pollution is what you are risking that environment to contain.

[00:33:05]Then it says, "Suggest a method you would use to minimize the challenge you have stated."

[00:33:11]How exactly would you minimize land pollution? It's simply to collect garbage and throw it to uh hazardous waste facilities that have been permitted by government. So, the best way is simply to treat of course by the council to treat and dispose.

[00:33:34]Okay? To treat and dispose wastes in permitted hazardous waste facilities.

[00:34:00]Okay? That's where you throw them.

[00:34:02]Okay? In permitted hazardous waste facilities. Areas that have been permitted by uh the council uh facility.

[00:34:13]The models labeled A, B, and C are for the three states of matter.

[00:34:20]The melting and boiling points of substance E are also shown in the table.

[00:34:24]Now, this substance has a melting point of negative 114.

[00:34:32]And then a boiling point of Now, this is what I want you to do.

[00:34:36]So, this guy has a melting point of -1 14.

[00:34:43]This same guy has a boiling point boiling point of 79 6° degrees. Now, I want you to see how simple this question is. The first question is saying which model represents the state of substance E at a temperature of pure melting ice. Now, pure melting ice melts at 0°.

[00:35:10]Right? Pure melting ice melts at 0°.

[00:35:15]Now, we have been taught that this compound here that we have it has a melting point of -1 14. So, anything that is above 114 and as long as it is less than 79, because this is the boiling point. So, anything that is going to be above 114 to this particular substance E, it should start melting. It should be in its liquid state. So, because 0 is greater than -114 or in other words, 0 is falling above 140 and also it is falling above 140 and also it is less than what? It is also less than 79. So, because it is falling in between -114 and 79, meaning it is a liquid and that is why Okay, it is going to be B. So, which model represents the state of substance E at a temperature of pure melting ice?

[00:36:14]Pure melting ice is 0 and according to substance E, 0 is in its liquid state, which is B.

[00:36:24]Which model represents the state of substance E at a temperature of pure boiling water at sea level? Now, the boiling point of uh pure water at sea level, what did I say? I said it is 100°.

[00:36:43]Now, because 100 is above 70 9, that implies that this guy here is in its gaseous state. And gaseous state is simply C.

[00:36:57]So, that's how you're going to put your C here.

[00:37:01]Then they say, "Which model represents the state of substance E at room temperature and pressure?" Room temperature and pressure, you have 25°.

[00:37:15]Celsius.

[00:37:18]25° is room temperature and pressure.

[00:37:23]Now, 25° is above -114, and it is less than 79. Meaning it is also falling in between. And in between, what did we say? Liquid, which is B.

[00:37:37]It's melting.

[00:37:40]Okay? That's how you answer that particular question.

[00:37:44]We go to the next question, which is going to be B2.

[00:37:48]The electronic configuration of element J is So, we've been given that electronic configuration.

[00:37:56]J is not the actual chemical symbol of an element of on the periodic table.

[00:38:02]Then they say, "In which group?" Look at this. This is J.

[00:38:06]Right?

[00:38:08]And this is his electronic configuration. I want you to look at this properly.

[00:38:17]So, whenever you are dealing with electronic configuration, the last number that they put is always very important because the last number is what will tell you the group. I said the group, not the period.

[00:38:32]It will give you the group.

[00:38:35]Okay? The last number will tell you the group.

[00:38:39]Now, these numbers one, two, three, four, five are telling you about the period.

[00:38:50]So, when you count them, you find the period. The last The last number in the electronic configuration is telling you the group.

[00:38:59]So, now, in which group of the periodic table is element J found?

[00:39:05]Okay? In which group of the periodic table is element J found? So, what did I say? The last number is telling you the group. Very good. It is in group one. So, you're going to say this is found in group one.

[00:39:20]Explanation, because it only has one electron in its outermost shell.

[00:39:43]Don't you see? One valency electron in its outermost shell. Very good.

[00:39:54]You go to the second one.

[00:39:57]It says, "Period of the periodic table is element J found." So, they want us to find in which period of the periodic table is this element found? Let's calculate the period. So, this is going to be period one, period two, period three.

[00:40:16]This is very simple. Period one, period two, period three, period four, period five. In other words, you count these are shells. So, shell one, shell two, shell three, shell four, shell five. So, because we have got five shells, the number of shells tells you the period. So, this is Z in period five.

[00:40:41]Don't forget this in your exam. Period five.

[00:40:45]What is the explanation? It's because it has five shells occupying the electrons. Okay?

[00:40:52]Being occupied by electrons.

[00:40:55]So, you can say because it has five shells being occupied by electrons.

[00:41:14]Simple.

[00:41:19]Name an element in group five which is in the same period as element J.

[00:41:25]Okay? Name an element in group five which is in the same period as element J.

[00:41:34]Okay? So, they want you to find an element. So, you go on the periodic table.

[00:41:44]You go on the periodic table.

[00:41:47]You check where group five is. So, this is how you move. This If this is a periodic table, right?

[00:41:55]If this is your periodic table, whenever you're going down, okay?

[00:42:00]Whenever you're going, let's say this is this is your periodic table is If you're moving in this direction, these are your periods.

[00:42:08]So, you've got this this first one is period one.

[00:42:12]Sorry, this one is group one, group two, group three, and group four. Okay?

[00:42:22]That's how it is.

[00:42:30]Then whenever you're going downwards, that is your period. Sorry, unfortunately I I I think the the the periodic table is at the far end.

[00:42:44]So it will be very unlikely for me to scroll.

[00:42:47]But if you get your periodic table, just do what I have done.

[00:42:51]So if you check properly, you want to name an element, of course, which is in the same period as element J. So make sure you go find the period. So go downward from hydrogen one, where lithium is two, where sodium is three, where potassium is four, going downward, then we are on five. Five, what we have?

[00:43:14]We've got uh rubi- rubidium.

[00:43:17]Okay? Rubidium, just underneath uh potassium. So going downward, those are periods.

[00:43:25]Now they're saying in group five. Let's see group five.

[00:43:29]Group five.

[00:43:30]So group five, 1 2 3 4 5.

[00:43:36]Okay.

[00:43:38]I'm going to just pick uh uh rubidium because it's an element also which is found in the same period as element J. So rubidium, I think we can get rubidium. It's okay.

[00:43:52]Rubidium.

[00:43:57]Okay, so this one was actually a one mark, quite simple because you just needed to pick it from the periodic table.

[00:44:04]A B3 is saying an anhydrous iron three chloride salt can be prepared by reacting a hot iron metal and chlorine gas in a combustion tube. What does the term anhydrous mean?"

[00:44:19]Okay, so anhydrous is simply a substance that contains no water of crystallization.

[00:44:26]Okay?

[00:44:28]So, you can say a substance that contains no water of crystallization.

[00:44:53]State the method by which iron chloride is prepared.

[00:44:57]Of course, the method is called direct combination.

[00:45:04]Method is called direct combination.

[00:45:11]Write a balanced chemical equation for the reaction between iron metal and chlorine gas. This is where I wanted to really uh focus much.

[00:45:20]They're saying, "Write a balanced chemical equation for the reaction between iron metal between iron metal and chlorine gas."

[00:45:34]Now, this is what is reacting, but I want you to pay extra attention to what I'm going to do.

[00:45:40]To form iron three chloride. How is iron three chloride formed? Because we know that iron three looks like this.

[00:45:48]Then a chloride looks like this. So, iron three chloride is going to look like this if you form it.

[00:45:55]Okay, sorry, this is supposed to be a two, of course.

[00:45:59]Okay?

[00:46:00]So, sorry.

[00:46:02]Chloride only contains Let me see, single group seven Okay, seven minus eight negative one.

[00:46:10]Guess.

[00:46:12]So, it only contains a negative charge.

[00:46:16]Of course, when they exchange, you're going to have iron there.

[00:46:20]Chloride, sorry.

[00:46:24]Chloride is going to contain a three here. This is what you call iron three chloride.

[00:46:28]So, this is what was being produced. So, what do you do? Write an equation. Your equation is going to look like this.

[00:46:37]You're going to have iron.

[00:46:41]Okay, iron, which is a solid. Make sure you put also the signs, solid or the states.

[00:46:47]Plus chloride.

[00:46:50]So, a chloride is simply a gas.

[00:46:52]It's producing iron three chloride. So, iron three chloride we've already seen how it's written.

[00:47:00]Now, we need to balance this particular uh chemical equation.

[00:47:05]So, let's check how we are going to actually balance it.

[00:47:14]Okay, sorry. So, this is supposed to be a chloride. Chloride is has two diatomic It's a diatomic molecule.

[00:47:20]Chloride is a diatomic molecule, meaning it has two chloride molecules, two chloride atoms.

[00:47:28]Okay, now let me see properly.

[00:47:31]Iron is reacting chloride molecule producing iron three chloride.

[00:47:38]Wow.

[00:47:39]How do you balance it?

[00:47:41]So, first of all, we can balance the the the chloride.

[00:47:48]Let me see. How many chlorides do we have? We have got three chlorides this side.

[00:47:53]This side we have two. So, how about if we put a three here?

[00:47:58]It implies that we're going to have six chlorides. This side we're going to have three chlorides. So, I can put a two here.

[00:48:07]So, I'm going to have six chlorides this side, six chlorides this side. Chloride is balanced. How about iron? It's not.

[00:48:13]I've got two iron this side. I can put a two here, and that's my balanced equation.

[00:48:19]Now, let me see what I'm going to have.

[00:48:20]So, this is going to be two iron in its solid state plus uh three chloride.

[00:48:29]Chloride is a diatomic molecule. In other words, it has two molecules two atoms. And this is going to be your iron.

[00:48:38]And then this is going to be chloride three.

[00:48:42]Uh this one is going to be a salt.

[00:48:45]So, in aqueous state.

[00:48:48]Okay, that is going to be a balanced equation.

[00:48:51]Uh we would give you a full mark for that.

[00:48:53]Uh describe what would be observed if sodium hydroxide solution was added to drop by drop to a solution of iron chloride in a test tube.

[00:49:04]Okay?

[00:49:05]Of course, you would be able to see this uh reddish-brown precipitate of iron three being formed. Okay?

[00:49:13]You'd be able to see a reddish-brown precipitate of iron three being formed.

[00:49:18]Okay?

[00:49:23]A reddish-brown iron precipitate.

[00:49:43]You even get all the marks. Okay?

[00:49:48]You are entitled to get all the marks after doing that.

[00:49:53]We go to the next question.

[00:49:56]Okay?

[00:50:05]We go to the next question. Let's see what's there.

[00:50:10]All right.

[00:50:11]This is so amazing.

[00:50:14]So, Okay, let me check.

[00:50:18]Do we have Okay, we have calculated this.

[00:50:21]We now come to more concept. They're saying 4.0 g of impure iron oxide reacted with uh 600 cm³ of 0.1 mol per cubic decimeter sulfuric acid.

[00:50:36]Then they say construct the balanced chemical equation for the reaction.

[00:50:42]Okay, we construct a balanced equation for the reaction.

[00:50:49]So, this is impure iron uh 3 oxide.

[00:50:54]So, let's check how does iron 3 oxide look like.

[00:50:59]The same thing. We're going to be We're going to have iron 3.

[00:51:03]Then oxygen.

[00:51:05]Like this.

[00:51:07]Then this guy is going to come this side. This guy is also going to come this side.

[00:51:11]So, expect iron 3 to look like this.

[00:51:15]Now, they're saying it is reacting sulfuric acid.

[00:51:18]So, iron 3.

[00:51:22]So, Okay, let's do this.

[00:51:25]Iron 3 oxide reacting with sulfuric acid.

[00:51:36]What is going to be formed?

[00:51:38]So, of course, you're going to form iron sulfate. How is iron sulfate going to look like?

[00:51:44]Okay, iron sulfate is going to look like this.

[00:51:48]So, this is going to be your iron three and a sulfate.

[00:51:58]So, this can come this side this this side.

[00:52:01]Then you're going to have something which is going to look like this.

[00:52:04]Your iron is going to have a two here, which is coming from the top.

[00:52:09]You open the bracket.

[00:52:11]Then the three from iron will come here.

[00:52:15]So, this is what is going to be produced.

[00:52:24]Right?

[00:52:25]This is iron three sulfate. Plus what?

[00:52:29]Iron three sulfate is solid. You are reacting in an acid. What you're going to produce is water at the end.

[00:52:38]Okay?

[00:52:39]Water. Now, let's check if it is balanced.

[00:52:43]Uh how many iron do we have this side?

[00:52:46]We have two irons this side. Iron is balanced. Oxygen. This side we have 12 oxygen on my left.

[00:52:55]12 oxygen this side. How many oxygen do we have?

[00:52:59]This side we have about 13 oxygen.

[00:53:01]So, because we have 13 oxygen, we can balance them up.

[00:53:06]So, if we put a three here, sorry.

[00:53:15]If we put a three here, how many oxygen do we have?

[00:53:19]So, this is going to be 12 plus three 15.

[00:53:22]15. And then if we put a three this side, how many are we going to have? So, three multiplied by four 12 12 plus three is 15. So, oxygen is balanced. What else should we balance?

[00:53:38]Okay, now this is a balanced equation because every other thing is a uh balanced.

[00:53:43]Okay?

[00:53:45]All right, this is beautiful. It's balanced.

[00:53:48]So, let's just put the states. So, this one is solid.

[00:53:52]This one is aqueous.

[00:53:55]This one is aqueous.

[00:53:57]This one is liquid.

[00:54:00]So, this is what is going to be formed. F two oxygen three solid plus three H two Okay, this is a sulfate, of course.

[00:54:17]It's in aqueous state.

[00:54:20]And then, this is producing iron two sulfate which is going to be in aqueous plus three H2O.

[00:54:39]Which is a liquid. That's how you calculate your balanced chemical equation.

[00:54:44]Now, they are saying calculate the mass of the pure oxide that has reacted with the acid. So, they want us to calculate the mass of the pure oxide.

[00:54:54]But, let me see what we have. They are saying 4.0 g of impure iron oxide reacted with the 600 cubic centimeters of this of sulfuric acid.

[00:55:05]So, from here, the first thing that we are going to do, of course, we can try to use the mole to mole ratio.

[00:55:15]Okay, we can try to use our mole to mole ratio. We see what we are going to have. The same concept that I actually taught is what we shall basically uh use.

[00:55:28]Now, remember that we have the we have this volume, we have this number of Okay, this is the volume, this is the concentration.

[00:55:38]So, let's calculate the number of moles of sulfuric acid.

[00:55:43]So, the number of moles of sulfuric acid is going to equal to Um let me see. Do we have the concentration? We do have the concentration.

[00:55:55]So, that I don't confuse you, let me just write the formula. Concentration is equal to number of moles over the volume.

[00:56:01]Uh the concentration that we're given is 0.1.

[00:56:05]Uh the number of moles we don't have them. That's what we're looking for.

[00:56:10]Now, the volume is in cubic centimeters, so convert it into these units, which are decimeters. So, you just say 600 / 1,000 1,000 / 0.6 Then, you cross-multiply. You're going to get n is equal to 0.

[00:56:34]0.1 multiplied by 0.6.

[00:56:39]We're going to have 0.06 moles of sulfuric acid.

[00:56:49]Now, we can use the 1:1 ratio.

[00:56:52]So, we have iron three.

[00:57:00]Okay, we're going to compare it with what we know, we already have.

[00:57:10]From there, how is the mole to mole ratio? Here, we only have one mole.

[00:57:17]Here, we have three moles.

[00:57:21]From the balanced chemical equation.

[00:57:23]Then, here we have x, that's what we're looking for. Here, we already have the number of moles.

[00:57:29]We can cross-multiply. You're going to have 3x is equal to 0.06 over 3 over 3 over 3 when this side.

[00:57:39]So 0.06 / 3 You're going to get something like 0.02 moles of what?

[00:57:50]Of iron 2 of sorry of iron 3.

[00:57:56]2 g moles of iron 3.

[00:58:05]Now after we find the moles of iron 3, they are saying we find the mass, right?

[00:58:10]So we need to find the mister.

[00:58:14]Okay?

[00:58:15]We can try to find the mister of iron 3.

[00:58:19]So how do you find the mister of iron 3?

[00:58:21]This is going to be our iron 3.

[00:58:26]So iron Let me check iron on the periodic table.

[00:58:38]So iron is uh 56.

[00:58:42]So 2 * 56 2 * 56 is 112.

[00:58:52]Then of course we can calculate for oxygen.

[00:58:57]It's going to be 3 * 16 16 48 48 + 112 160 Now notice that we have found 160 as the mister.

[00:59:17]Now we can find the number of We can find the the mass of the pure oxide.

[00:59:23]How do you find the mass? Simple.

[00:59:25]Number of moles is equal to mass over mister.

[00:59:30]The mass is going to equal to the number of moles we calculated to be Sorry, no not these ones.

[00:59:38]The number of moles we calculated to be 0.0.2.

[00:59:42]Okay, this one for the oxide. So, you're going to get them.

[00:59:49]So, you're going to say 0.02.

[00:59:52]Then we're going to multiply it with the mister which is the 160.

[00:59:58]Your mass is going to be 3.2 g.

[01:00:11]So, this is going to be your mass.

[01:00:14]Now, the question is saying we calculate the percentage purity.

[01:00:18]Simple.

[01:00:19]Okay?

[01:00:21]Percentage purity is going to equal to Let's check. So, just go back to there's no need to waste time because you are in the exam.

[01:00:34]Just get what you have calculated. So, what you calculated is your 3.2 over what was already given in the question.

[01:00:42]The same amount of what I calculated in percentage yield.

[01:00:50]Okay?

[01:00:56]You will get your 80.0%.

[01:01:00]As your answer.

[01:01:02]Okay?

[01:01:03]So, this is how you solve this particular question.

[01:01:11]We go to this B5.

[01:01:14]B5 was actually saying study the sketch of the periodic table shown and answer questions that follow.

[01:01:21]Note the symbols of elements given in the sketch are not the actual symbols of the elements.

[01:01:28]And then this one is saying elements K, L, and P are all metals.

[01:01:35]Which among these is the most metallic element?

[01:01:39]Okay, so this is how it is on the periodic table. I'm a metallic element you are able to so I'm a metal if you are coming from the top So as you are coming from the top, you are going downwards, they even become more solid, more metallic.

[01:01:57]Okay? More solid or more metallic.

[01:02:02]So this is what happens. Or if you are considering a group you must be moving in this direction they become so metallic. So if you are moving from right to left. So meaning you are very metallic more.

[01:02:27]So you can use the groups and groups you be coming from your right going towards your left. They are becoming more metallic. I'm going to a period it means you will be coming from the top, I'm going to punch, they become more metallic. I want you to put that into your mind.

[01:02:45]Okay? I want you to put that into your mind to really be so much of help.

[01:02:51]In this case which one is so metallic? Notice that in groups, if we are moving in this direction it will last it will last last last, it's only K.

[01:03:02]The one which is at the far end is K.

[01:03:05]And if we are using periods, meaning we are going downwards, the one which is at the lowest point is the same K.

[01:03:13]So K is actually more metallic. So we are going to say element K.

[01:03:23]Element K.

[01:03:24]Reason?

[01:03:26]Simple.

[01:03:27]It is because the metallic character increases as you go down a group.

[01:03:36]And okay.

[01:03:37]Metallic character increases as you go down in a group. Okay?

[01:03:52]Sorry. I I just wanted to take some water.

[01:03:59]Metallic character increases as you go down a group or from right to left considering considering a period.

[01:04:42]So, if you're considering a period, you are in this direction and you are moving in this direction from right from from your right to your left. If you're considering a group, you are going downward. They become more metallic.

[01:04:57]All right. We are not giving up until we finish this particular lesson.

[01:05:02]We go to B. State one use of element S.

[01:05:06]So, element S it's here. So, let's go on the periodic table. It's actually helium.

[01:05:12]So, what is the use of helium? Helium is used uh for advertising signs or lighting. Okay?

[01:05:21]Used for advertising signs. If you go to other countries like Tokyo, you would be able to see so beautiful uh billboards, restaurant billboards and stuff.

[01:05:39]Okay?

[01:05:41]Or lighting. They are used for advertising signs or lighting.

[01:05:45]Even in China, even in Zambia of course we have on various pubs. Those lightings, you know, they look so nice.

[01:05:54]Okay.

[01:05:55]Then it says, "Metals have various properties and some harmful effects on humans. Explain why."

[01:06:02]Okay, it's because when these metals accumulate inside your body, they interact with your enzymes.

[01:06:08]They would be able to interact your your enzymes.

[01:06:12]Okay? Denaturing them or they would be able to have a negative side effect on your central nervous system. So let's say because when they accumulate in the body they would Okay?

[01:06:48]They would I would say, let me get a very good term. They would distort the function.

[01:07:04]They They distort the function of enzymes and affect the CNS.

[01:07:18]Okay, so most enzymes would actually be affected and enzymes are the ones that catalyze most of the reactions.

[01:07:25]So, if these metals accumulate, they would distort the function of most enzymes and eventually affect your central nervous system, which you don't want.

[01:07:36]Names of metals that form part of the reactivity series are listed as follows.

[01:07:41]We've got aluminum, we've got iron, we've got gold, we've got lead, we've got sodium.

[01:07:49]Then they say arrange the metals in the increasing order of reactivity.

[01:07:57]Starting with the least reactive at the top and most reactive at the bottom. So, I want you to answer this question. This question is going to be your homework.

[01:08:06]I want you to answer this question. I want you to submit this question to this number, 0777 664046.

[01:08:16]I want to test you. I want you I want to see if truly you understand the reactivity series. Please make sure you send uh the answer to this question to this particular WhatsApp number. I will need to mark you.

[01:08:31]From the list given, identify a metal whose metal hydroxide does not undergo thermal decomposition.

[01:08:39]So, there's only one metal which cannot undergo thermal decomposition. Thermal decomposition simply means if you increase the degree or the temperature either surpassing 1,000° C, it cannot decompose.

[01:08:56]It cannot lose its shape. So, how should you reason? It means that that um uh substance you're talking about should be so metallic enough.

[01:09:08]It should be so metallic enough, strong enough to resist the temperature.

[01:09:14]So, from your table of course >> [clears throat] >> only sodium is so metallic.

[01:09:22]Explain why aluminum is said to be unreactive despite its position in the reactivity series.

[01:09:27]The answer I already mentioned is because aluminum readily reacts with oxygen to form an oxide layer which prevents it from reacting with the more further oxygen. Okay?

[01:09:42]Because aluminum readily reacts with oxygen to form an oxide layer that prevents more further reaction.

[01:10:22]Hence making it unreactive.

[01:10:25]This is how you answer this particular paper. So, of course there are questions uh in section B that I'm going to answer especially in the next session of my lesson. It's going to be there. Okay? I'll make sure that you look you look for that lesson, you watch it. You go through, you get the concepts, prepare for your exam, and you'll be able to get almost everything.

[01:10:49]Please, if you found this video interesting consider subscribing right now, hitting the like button, and don't forget to share to others.

[01:10:57]Thank you so much.