THIS IS A CLEAN EXPO OF WAEC CHEMISTRY PRACTICAL, 2026

Added: 2026-05-09

[00:00:00]This one is for those who are preparing to write WAEC on their own. There are schools that don't entertain any form of expo and some students are really afraid. I am focusing on number two of your WAEC practical, called qualitative analysis or salt analysis. Now, this is how the question will look like. You are going to be given a white powdery substance. The substance will be labeled C. This substance will be in a specimen bottle like this. And they will possibly ask you to divide into three places. So, you use test tube and divide it into three places.

[00:00:37]This is the first portion, second portion, third portion. There are four questions that they can ask you. To the first portion, they will ask you to heat.

[00:00:46]I will tell you the reason. To the second portion, they will ask you to add iodine solution. To the third portion, they will ask you to add hydrochloric acid or nitric acid. The same third portion, they will ask you to add potassium iodide. Why all these questions? Now, note, they may ask this one first followed by this one and followed by this one.

[00:01:10]Or they may ask this one first followed by this one and followed by this one.

[00:01:14]Whichever sequence it comes, the most important thing is to understand why they are asking the question and how to solve it. Now, let me start from here. If they ask you to heat, this heating is to verify if there is an organic compound inside this sample. Whenever you heat an organic compound, it turns black, proving that it is made up of carbon.

[00:01:39]So, whenever you heat, the substance will turn black. And when it turns black, you observe. Under observation, you write black residue. And under inference, you write organic compound present. That's the response they want from you.

[00:01:55]Here, they will ask you to add iodine solution to the second portion of the same sample. Why? They want you to confirm if that organic compound is starch. So, when you add iodine solution, you are testing for starch.

[00:02:10]And the observation is what? Blue-black coloration observed. And when you write blue-black coloration, under inference, you write what? Starch present or the organic compound is starch. On the third portion, they will ask you to add either hydrochloric acid or nitric acid to the sample.

[00:02:31]This sample is not soluble in water, so they will not ask you to add water.

[00:02:35]They will ask you to add any of these acids.

[00:02:38]These acids will dissolve the sample somehow.

[00:02:42]And during the dissolution, gas is released.

[00:02:46]And the gas is carbon four oxide. And that is why they will even ask you to test any gas evolved with lime water.

[00:02:54]Right? So, you will test the gas with lime water.

[00:02:59]So, that gas will be passed to lime water. So, after adding this acid, you see effervescence, fizzing.

[00:03:08]A gas that is colorless and odorless is evolved. And when you test it with lime water, it turns lime water milky. The only gas that does this is carbon four oxide. So, after adding this and you experience effervescence, you write effervescence. A colorless, odorless gas which turns lime water milky evolves. Then under inference, you write the gas is CO2 because this gas is coming from a carbonate or hydrogen carbonate. Meaning that one of the components of the sample is a carbonate salt. So, under inference, after writing CO2, you now write from carbonate or hydrogen carbonate. Carbonate is CO3 2 minus. Hydrogen carbonate is HCO3 1 minus. Then you add They ask you to add potassium iodide.

[00:03:54]Potassium iodide there.

[00:03:56]You are using this potassium iodide to precipitate a possible metal. If there is any soluble metal there, the metal that dissolved in acid, potassium iodide helps to precipitate it out as an insoluble iodide. So, when you add potassium iodide, a yellow precipitate will form. This yellow precipitate is lead to iodide. So, what you do is under observation, you write yellow precipitate. And under inference, you write lead two ion present, PB 2+.

[00:04:30]Present. So, from all these, you can now answer your question in a tabular form. And this is the table.

[00:04:40]You write test, observation, inference.

[00:04:44]So, under test A. So, you say C plus heat. And what did I say about heat?

[00:04:50]When you heat, you see black residue.

[00:04:54]And when you see black residue, organic compound is suspected. Organic compound present. Draw your line. Second question. They want you to confirm if this is actually organic compound by asking you to add iodine solution to the second portion. So, you can say second portion plus iodine solution. And once iodine solution goes there, you have blue black color.

[00:05:19]And the inference is under inference, what turns blue black when it comes in contact with iodine?

[00:05:25]It's starch. Confirmed. C. So, we are through with discovering that the sample contains an organic compound which is starch. So, what next? The next is third portion.

[00:05:37]Third portion plus what? HNO3 or HCl.

[00:05:42]When you add this, C dissolves, effervescence occurs.

[00:05:47]A colorless, odorless gas. Remember, they will ask you to test this gas with lime water. So, you will you also explain the behavior of gas inside lime water. You now say which which turns lime water milky. Now, here you say the gas is CO2.

[00:06:08]And then, carbonates, hydrogen carbonates present.

[00:06:12]The next, number D. They will ask you a question on this chemical mixture. So, sample, that is this sample from from here, C, plus potassium iodide. If you add potassium iodide, that is the time it will go and precipitate the lead ion in form of lead iodide, which is yellow in color. So, what you will see under observation is yellow precipitates. And once you see it, this is the confirmation of lead lead ion present.

[00:06:46]So, this is the number two salt. No serious issue, no stories. And if you got value, share this video as wide as possible. Support the channel by clicking on subscription button.

[00:06:57]And do have a wonderful day. Bye.