NECO 2026 Chemistry Theory Questions & Answers 100%

[00:00:00]This is the part B video. So, request for the part A video in the comment section. So, solution A is this is this and what is the answer? Which one is the most acidic? You know, on number line on the sorry on pH scale, we have like a 1 to 0 to 14. 7 14 here. So, from here is most acidic.

[00:00:22]Here is neutral.

[00:00:24]And here is most basic. So, meaning that if one is a 2 3 4 5 6 8 9 10 11 12 13 here.

[00:00:39]So, all these ones they are acidic.

[00:00:42]All these ones they are basic.

[00:00:45]This one here is neutral. So, now which one is the most neutral?

[00:00:50]Sorry, which one is the most basic? So, let's go from it. So, most the most basic is this. Like the basicity increases like this.

[00:00:59]So, the most basic is 12. So, the answer here is 12.

[00:01:04]The acidity increases like this. You understand?

[00:01:07]So, the neutral is 7. So, which is this?

[00:01:12]The neutral is 7, which is this. And which one is the most acidic? Most acidic is 2. So, the answer here is 2.

[00:01:20]We have done that. Can you see? So, you have answered that. Although, 5 2 is also acidic, cool, but not most acidic.

[00:01:27]8 is also basic, but not most basic. So, that's that about that. Now, let's move to question number two.

[00:01:35]Question number two said that we should calculate the mass. The mass, okay. So, that's um That's um I've This type of question was done in my um part one video. So, solubility or molarity, anyone you call it.

[00:01:48]Molarity equals to mass over molar mass mass over molar mass times 1,000 over volume. This is the formula. So, what's the mass? The mass is what we are Okay, the mass is what we are looking for, right? So, 0.2 equals to X over the molar mass of this is what? Of Na2CO3, that'll be 23 * 2 plus 12 plus 16 * 3. So, by the time we add it up, then that'll be times 1,000 over The volume is what? The volume is going to be 250, right? Good. So, now let's continue this. Okay, let me just put it down here. 0.2 That is equal to X all over 23 * 2 23 * 2 So, that's 46. 46 + 12 That's a 58.

[00:02:45]So, 58 here plus 16 * 3 is what?

[00:02:50]16 * 3 is 48. Okay, so plus 48 multiplied by 1,000 over 250 is 4.

[00:02:58]Can you see that? 1,000 over 250 is what? It's 4. So, let's continue here.

[00:03:03]Then that will be 0.2 equals to 4X over 58 + 48 is what? 58 + 48 That's 106.

[00:03:15]106. So, what do I do? I'll cross multiply. And that's going to be 0.2 * 106 equals to 4X.

[00:03:27]So, 0.2 * 106 equals to 4X. So, 0.2 * 106 Then that's going to be 21. 21.

[00:03:40]21.2.

[00:03:42]So, 21.2 equals to 4X. And X equals to 21.2 over 4. And if you divide that, then the answer is giving you 5.3 g.

[00:03:55]So, X is giving you 5.3 g and that's the value for the X. Okay?

[00:04:02]That's the value for the X. Now, let's go to the third question.

[00:04:08]The question said we should write the You can already Okay, you can see the question here. So, this is solution for the third question.

[00:04:15]Magnesium ion Mg2+ initially supposed to be 12, but it has lost two electrons.

[00:04:22]So, we have it as 10 like that. That'll be 1s2 2s2 2p6.

[00:04:29]This is correct answer. 1s2 2s2 2p6 because it has lost two electrons, so we are going to stop at 10. And that's that. This for the A. And then for the B, for the B, the B is going to be give one difference between endothermic and exothermic. So, let me underline it. Let me tabulate it rather. So, here is the A. Let me give you as endothermic.

[00:04:54]And let me give you as exothermic.

[00:04:59]So, for the endothermic, that one simply means that heat is absorbed from the surrounding.

[00:05:07]Heat is absorbed from the surrounding.

[00:05:20]So, and then delta H is going to be positive.

[00:05:24]Yeah, for endothermic. Why for exothermic, heat is released or liberated to the surrounding.

[00:05:43]So, that means the heat delta H is going to be negative.

[00:05:49]Okay, that's that for question number three. Now, let's move to question number four.

[00:05:55]Question number four says that we should attempt this question here. Say we should calculate the pH of this guy. For you to do this, you have to dissociate this H2SO4.

[00:06:05]So, if we do this, that will be 2 H+ with SO4 2- So, the whole we have is 0.01 molarity. 0.01 0.01 So, for this hydrogen is going to be 2 * 0.01.

[00:06:22]So, if you multiply this, that should be 0.02. But, let me do that. 2 * 0.01 So, that's Okay, sorry. 2 * 0.01 That's giving me a 0.02 mol/dm³.

[00:06:39]Yeah, mol/dm³. As you can see that.

[00:06:41]Okay. So, now then let us find the pH.

[00:06:44]pH equals to -log 10 H+. So, that will be -log 10 What's the H+ there? 0.02 So, let's find log 0.02 is what. Log 0.02 is giving us That will be 1.6989.

[00:07:07]Sorry, -1.6989.

[00:07:10]So, by the time you now, you know, minus times minus That's going to be plus. So, we have it as 1.6989.

[00:07:18]Approximately 1.7.

[00:07:21]So, the pH is giving us 1.7 for this question number four. Now, let's move to question number five.

[00:07:26]So, question number five That's the That That will be this. For question number five. So, that says that we should calculate the number of moles from this. Looking at the This is This is ideal gas equation. PV equals to nRT.

[00:07:43]So, we are asked to look for n. So, n equals to PV over RT. So, n what's our pressure? Pressure is the dm is the atm. That's two multiplied by the volume is in dm cube. That's 10.

[00:07:57]Over the r is a gas constant. That is 0.082 multiplied by while the temperature though we are given in degrees Celsius, but let's convert it to Kelvin. That will be C plus 273 equals to K. So, that will be 10 plus 273 and that is 283 Kelvin. So, I'll multiply by 283.

[00:08:21]283. So, continuing that that will be 20 all over then let me multiply 0.

[00:08:30]0.082 multiplied by 283 and that will be This is 23.206.

[00:08:41]So, finally my number of mole is going to be 20 divided by that. So, sorry. So, 20 divided by 23.

[00:08:53]206 and that is giving me 0.86184.

[00:09:00]Whereby if I should approximate it, that's 0.86 mole.

[00:09:06]So, that's the answer for that. Now, this is what I have for you. Yeah, ensure you watch the part of the video.

[00:09:10]Sorry, the video is not really very sharp because I didn't on my lights like my LED lights. That's why it's not really very sharp. So, please enjoy. Manage it like this. Now, see you my next video.

[00:09:21]Bye.