2026 WAEC Chemistry Practical | Qualitative Analysis | Episode 2 (Tests & Results)

Added: 2026-05-12

[00:00:06]So it seems our filtration is almost complete but uh there are still some drops of the filtrate. So what we'll do is we've transferred this here. I like to continue dropping because don't want any part of the filtrate to interfere with the analysis of the residue. So we're going to carry out the analysis of the filtrate. Yes, going to car analysis of the filtrate. First off, we are going to test for the pH of the filtrate using um blue litmos paper. So this blue litmos paper.

[00:00:51]Okay. So, we're going to take um a strip of this.

[00:00:59]All right.

[00:01:04]And check to see whether the filtrate will be uh neutral or or acidic solution.

[00:01:14]The filtrate can see can you see the filtrate turns blue lead must paper red which means that the filtrate is an acidic solution which is um correct because this filtrate is a solution of lead 295 which is a product of a weak base that's lead 2 hydroxide and a strong acid trit 5 acid. to it which is why it under goes hydrarolysis to form an acidic solution.

[00:01:47]All right. So now we are going to carry out different tests on the filtrate to test for the presence of the cat ion. So first off so we'll divide this into three different um uh portions. one two just little portions.

[00:02:26]All right.

[00:02:33]And then three Okay. So in the first in the first portion we're going to carry out the test on the filtrate using [snorts] what?

[00:02:49]AUS sodium hydroxide. So we'll be testing for the cation using a sodium hydroxide.

[00:02:58]So first of all add it in drops.

[00:03:04]You expect a white precipitate in drops. Can you see? Yeah. I'm not adding excess. If our test is correct, this precipitate should dissolve to give us a colorless solution in excess sodium hydroxide.

[00:03:26]Oh yes, it has dissolved.

[00:03:33]So you can see that means that the iron present the cation present can either be zinc aluminium ion or like two iron but it cannot be zinc and aluminium because it is not amphoteric. The precipitate is not amphoteric. So it can either be le 2 ion or calcium ion. The calcium ion is not soluble in excess sodium hydroxide.

[00:04:04]So it means that that can only be what?

[00:04:08]Le two ion. But we are not sure. Let's carry a further test using um HCl right with HCl is meant to give us a white precipitate right of lead 2 chloride which will dissolve on warming. If we put the white precipitate in hot water it will dissolve right to give us a clear solution but on standing it will reappear. So let's just see what will happen if we add sodium hydroxide sorry hydrochloric acid to this.

[00:04:52]Oh you can see the white precipitate there.

[00:04:57]All right. So we expect this white precipitate to dissolve on when in hot water. So we are trying to heat our our water. We'll come back and put that there. So meanwhile, let's test with ammonium ion. Sorry, a ammonia.

[00:05:21]Ammonia will give us a white precipitate in drops that'll be insoluble in what?

[00:05:26]Excess.

[00:05:30]Yes, white precipitate in drops and also what in excess. All right. So, but let's even confirm whether there's a confirmatory test that we can use to confirm whether lead 2 ion is actually present without necessarily using HCl. We can use potassium iodide.

[00:05:58]Although this is not part of the requirement but I just had to bring this in right to just confirm to us that what we are working with is lead two trios nitrifi. If it is lead two that is present lead two ion will react with potassium iodide to form a yellow precipitate of lead iodide. Hold on.

[00:06:32]Can you see this? Okay.

[00:06:43]So, let's add this this lead this potassium iodide. Can you see that?

[00:06:48]Okay. So, we add this.

[00:06:54]Wow.

[00:06:55]Can you see [snorts] that's already a yellow precipitate even without mixing completely?

[00:07:03]Wow. So I don't even need to carry out the um warming of [snorts] this um lead 2 chloride to see what it will dissolve. It will definitely what dissolve because potassium iodide has confirmed that it is lead two ion that's what present. So in your own case you can put this in hot water right and leave it for some time. You see that after some time it will dissolve and when you remove it from the hot water and allow it to stand the white press will do what? Reappear. All right. So after this let's now move to our residue. So this is our residue. Can you see it? Can you see the white deposit?

[00:07:49]Yeah. On the filter paper. Yes, that's a starch. So, we are going to collect it and put it in um in a test tube and then add few drops of iodine to it.

[00:08:04]All right, hold on.

[00:08:08]This is iodine. You see this? So, we add few drops of this guy to this. Okay? And then you'll see the result. So, I'm going to take a portion of this. Yeah.

[00:08:22]Can you see it? Yeah.

[00:08:30]Okay. Okay. Whatever. I just allow it.

[00:08:37]It's jelly like, right? So, all what I want is a blue black coloration when once iodine drops on it. Okay. So because of it jelly like nature it's making it difficult to um be added to the test tube but or boiling tube. I'm not that's not a problem.

[00:09:02]I have a little quantity that I need.

[00:09:05]So, I'm going to turn I'm going to take a little portion of the solution.

[00:09:16]Let me remove this.

[00:09:20]I want you to see everything that I'm doing.

[00:09:25]Okay. Just a little portion.

[00:09:29]So I use my drop pipet. [clears throat] Yeah. So when once I add it to this guy, this will turn what? Blue black.

[00:09:48]Can you see?

[00:09:56]>> [screaming] >> What do you notice?

[00:10:08]Can you see?

[00:10:10]It gives us what a blue black. Can you see the side? Can you see the side of the Can you see the blue black coloration there?

[00:10:21]Can you see the blue black coloration?

[00:10:30]Can you see the blue black coloration?

[00:10:32]What does that tell us? That tells us that starch is what? Present, right?

[00:10:38]That is the starch is what? Present. So that's all about is what you expected doing the qualitative analysis.

[00:10:44]Meanwhile, look at this. Can you see the first samples that I dissolve in water? This is your lead transcarbonate 4. Remember, you can see that it is insoluble in water. And this is your starch. You can see that starch is insoluble in water.

[00:11:03]And which is why I would not advise you to try to use water to separate them.

[00:11:08]The best solvent to be used for the separation is what? Dilute HNO3. All right. So, let me know what you think in the comment section. Thank you for your time. God bless you until I come your way next time. So, watch out for questions, possible questions on qualitative analysis and voluntary analysis. Thank you for watching.