2026 WAEC Chemistry Practical Titration Explained (Full Guide + Answer Format)

Ajouté : 2026-05-17

[00:01:30]Hello guys, the long awaited practical is here. I've had lots of people message me about this practical but you should know that we're always working you know we always working under me to give you a wonderful and interesting practical. So we are here again. So if you are writing why this year you are a tutor you are actually preparing student for this exam or you a student yourself you have seen this video then you are very lucky I want you to pay maximum attention today I'm going to give a lot of instructions I'm going to give a lot of warnings especially to student that are watching this and to teachers and I'm going to give us a predicted questions for this year exam it's going to be an interesting one the questions are very interesting the titration the qualitative analysis they are very very interesting and I want to speak to co-educators we have created a group already for teachers so that we can deliberate we can analyze a whole lot of teachers are there if you think that interests you and you want to join us to be you want to partake of the prediction the analysis and the professional guidance we're going to be giving just for mastery for clarity and for confidence so that our students we do well because for our student to do well it depends on us what is the instruction we are giving them How have we prepared the reagent? So all these things are being discussed in the group. So I want you to if you feel that interest you and you want to join us, kindly chat the number on the screen so that you can join us. But very quickly today, if you are just watching this YouTube channel for the very first time, kindly click on the you know subscribe button and turn on the notification bell so that when we upload this video, you are going to be notified. Now for today, please I want us to pay maximum attention. Let me quickly run through the titration. Let me run through the titration. I have my bett already. I have my predicted question, but I want to titrate.

[00:03:24]Hopefully, I'm going to be shooting two videos for this titration because the titration is between H2S04 and sodium hydroxide. H2SO4 is a strong acid.

[00:03:33]Remember, sodium hydroxide is also a strong base. Remember, so we can use any indicator is either we use melty orange or phenotapine. So but today I'm going to be using phenot then I will shoot another video with another predicted question to use maturing. You can be asked to use either of this indicator on that day. So let me quickly run you through the practical. So this is my acid already in my boret. I have my acid already in my boret. So I want to pipet my base. This is my base. So in your various schools they're going to label the acid as a all right and the base as b. So let the let the acid be in the boret like I've done. I've actually filled the bret and the base you're going to pipet it slow. Let me quickly do that very quickly so that I will not waste our time.

[00:04:30]If you have been following my channel I have taught how you can manipulate your table. You don't need to waste your time on this. You don't need to waste your time on this.

[00:04:39]So this is the mark already. Then you can see that in my conical flax now.

[00:04:47]So I've said today I'm going to be using phenotaphne as the indicator. Don't forget strong acid, strong base. We can use any indicator. So I'm going to be using phenot. I'll shoot another video again. God helping me orange and give another predicted question so that we can practice all the things. And if you're not on the WhatsApp channel, you are missing a lot. They have given a lot of information a lot of other predicted question will be posted there. So please check the comment board section to join our WhatsApp link. So look at that you can see just two drops you can see it's changing the color to purple.

[00:05:23]Did you see that on using phenotene you can see the color then before I titrate you can see the funnel is there. One of the rules I have to remove the funnel.

[00:05:33]So let's go now. Let's see. Let's see the end point.

[00:05:38]Let's see what the end point is going to look like.

[00:05:57]Can you see that? You can see so end point is reached. You do you see? So if I'm using phenotapine is changing from purple to colorless. Can you see that?

[00:06:08]From purple to colorless. So let's check let's check our bat readings.

[00:06:16]So here I have let me take it up. Let me adjust this.

[00:06:23]Me adjust this.

[00:06:25]All right. Let me just adjust it up so that we can see. I've told you I'm going to do it once.

[00:06:31]I'm going to do it once.

[00:06:35]Let me tighten this so that Okay, let's bring the camera closer. Look at that.

[00:06:41]Did you see this is 12? So, this is around 12.20 I'm seeing. You can see it on the camera. 12.20.

[00:06:50]Can you see that now? Good. So, this is it. 12.2.

[00:06:55]That's what I'm getting for this. 12.20.

[00:06:58]Look at 12. 12.1 12.2. Some people record it as 12.3 you know we might not be seeing it but look at that 12.2 into 12.3. So I can use any of those values.

[00:07:08]So I DON'T NEED TO I HAVE I have told you student this. I don't need to waste my time BECAUSE WE HAVE TWO HOURS FOR THE EXAM and we are answering three questions. We are answering titration, we are answering salt analysis and we are asking number three which is theory of particle. So now I want to you know construct my table to agree with my title value. I got 12.2. You can use either 12.2 or 12.3. So let's come now the rough if you are not you know familiar with this you can just have your initial readings to be 0.00 0 0 what is the meaning of that my initial before I started the titration the volume of the acid was on zero here did you get that that's the initial which means what is the volume of the acid in the boret before I start titrating did you get that now that's zero so I am putting 0.7 to ease our stress saying that we refilled that's the meaning we refilled after every practical we refilled did you get that now so and don't forget Please come closer. Just get this. Let me quickly do something here. Now look at this. Let me quickly do something here. Just look at this. Look at this.

[00:08:20]Now I want to use 12.20 cm cube as my title value. I don't want to do more than one. You don't need to stress yourself. If you have been following my channel, you should know that by now. If you have been following this channel. So I want to use 12.20.

[00:08:37]Did you get that now? SO WHAT DO I DO FOR THE ROUGH? I CAN SHOOT IT UP a bit.

[00:08:42]I can just shoot it. You can say I got 12.2 directly. But you know just to add some spicy to our table. I can just shoot it up a bit. Telling them that when I did the rough I was not really accurate because of you know probably there will still be some remnant of water in the communical flax and the rest. So I assume so I can just add you know 12.20.

[00:09:05]I can just add around 0.30 to this. Did you get that? Just for the rough. So I have around 1250. So I'll come here. I'll say my rough is 1250.

[00:09:19]Did you get that? Now what is the title value I want to use? 12.20. Is that not?

[00:09:24]So I have 12.20 as my first. My second I can have 12.20 again. Then I'll just add 0.1 to this one. 12.20 0.10. That will give me 1230.

[00:09:39]So I will have 12.3.

[00:09:43]Did you see that? Now so at the end of the day my volume of acid I subtract this from this I will have 1250 12.20 12.20 12.3 Did you see that? Now now you can just do a lot of things. You can play with all these tables. I tell you, you can play with all these tables if you understand what I've been saying. Now look at this. I can still add my table.

[00:10:09]Look at this. I can add my table to be 12.50 as what? As the rough. Then I will call 12.20 that I want to use. Then I will have 12.10 and I will have 12.10.

[00:10:22]You can see just not notice something.

[00:10:25]And if you notice something between my first and my you know second and third the difference between them is just 0.10. It is important for accuracy sake.

[00:10:36]You can see my rough is far you know different from them. And that's the reason why when I'm calculating my average volume of acid used I will not use my rough. Did you get that now? I will not use my rough. So you don't need to keep titrating. Keep titrating. You should have mastered this because there is no time for the exam to really do all those things because you have two hours and you are answering three questions.

[00:10:58]Now let me say this please let me warn a whole lot OF STUDENTS. MY TITLE VALUE here doesn't really matter and this is why for every center they are going to give your teacher a report to fill. Please make do with the title value you are given in your center or the title value you have gotten in your center. Please I am passing this information to all student.

[00:11:24]You know some students are very funny.

[00:11:25]They go to school and say the chemistry hang out on chemistry hang out the title value they use is this. Why are we using this in our school? You are very wrong.

[00:11:33]Your teacher in your school has the final say. If your teacher is saying your title value there is 17. Please make do with that because he or she is going to get a report. Fill in the title value he or she got and that's what they'll be using to mark your center. So every center the title value must can differ or may differ in as much as that is what your teacher is saying he OR SHE GOT BECAUSE IN THE MARKING GAP IF YOUR TITLE VALUE IS FAR from your teacher's title value you are going to you know your mark is going to be deducted. Yes, your mark is going to be seriously deducted and it can affect you please.

[00:12:11]So note that. But if YOUR IF YOUR TEACHER has done the practical, you have done practical and they have given you title value to use, you should now know how to manipulate your tables or how to you know how to vary your table to agree with what your teacher has said or the title value your teacher has given you.

[00:12:28]So please my title value here that's just my own opinion. All teacher might not agree with me. It's fine. This is just my own opinion. This is just what I feel that I got. Some other teachers can got another thing differently. So I'm just trying to advise students and to warn them because I've had a lot of cases like that. There are a lot of students, you know, no that's not that's not how it's going to look like. So please make do with the title value in your center. For number one, if your teacher is saying this is the title value, please make do with that. I hope that is clear. That information is very clear. Please, that information is very VERY CLEAR. SO THAT IS JUST that all right that is that if you have been watching my channel for some time you should understand all this I have said this over and over again your one is understand how to you know vary your table to agree with your teacher's title value instead of you doing a whole lot of titration like that like that did you get so that is THE SO FROM HERE NOW WHAT IS THE NEXT THING WE ARE GOING to calculate the average volume of acid used so because from the question they Put A into the boret which we have done and titrate with 20 or 25 cm portion of B. We actually use 25 using phenotapin as the indicator. That's what we use from purple to colorless. Record the volume of your what? Pipet. We have recorded the volume of pipet. That's an instruction. They ask you to record the volume of your pipet. That's 25.

[00:13:52]Tabulate your boret readings. That's a tabulation. Calculate the average volume of acid use. So we are calculating the average volume of acid use. How do we do that? If you look at the rough is far far more different than there. All right? So, and please there is a lot of mark you can lose from this table if you're not very careful. There are something we call concordant values.

[00:14:14]Concordant values is when your values are similar there are marked for it. And if you check my own did you see I have out of the three I want to use two is the same. It shows accuracy. It shows precision. It shows you have done the practical very well and there are marks for all these things. So please I advise you just check all this thing practice it and you you'll be fine. ALL RIGHT. SO LET'S have the average now the average volume of acid used. So what is the average volume of acid used? I am picking 1 2 3. That's the first the second and the third.

[00:14:53]That's average and I'll be dividing by three. So which is just like me. So I will have 12.20 20 + 12.20 + 1230 divide by what? Three. So my average my average volume of acid used is equal to so let's have our calculator from there 12.20 + 12.20 20 + 12.30 / 3. So we are having 12.23 approximately to two decimal place.

[00:15:37]Please very important your average volume should be to two decimal place as cm cube. And let me speak to my co-educators. If you did not agree with my title value is fine. Just make sure that the title value you are recording your your student title value is very close to it. There's no issue. You can have you know variation in title values based on how we have prepared based on the purity of the compound. All right.

[00:16:03]So it could could vary but just make sure that the title value you are recording is very close to the title value your students are using so that it doesn't implicate them so that they don't lose unnecessary mark. So this is just my own opinion and that's just what I feel. All right. So let's move on now.

[00:16:19]SO WE ARE DONE WITH THIS. THEY SAID your boret readings and calculate the what average volume of acid used from your results and information provided.

[00:16:28]Calculate. So we are coming to the calculation now. Concentration of B in mole per dm. That's number one.

[00:16:35]Concentration of B in mole. Let me divide this. Concentration of B in mole per dmq. Let's go to the question. A is a solution containing impure tetraasulfate 6 acid containing 4.00 g in 250 cm cube of solution. But in the question they said concentration of B.

[00:16:55]So let's come to B. B is a solution of pure sodium hydroxide containing 4.00 g per dmp. So we are given the mass concentration of B. And I've told you that if you have been watching my channel if they ask us to calculate what the concentration of B in mole per dmpq WE THE FIRST FORMULA THAT SHOULD COME to your mind I've always said that mole is mass over what over molar mass. So let's check if we can use this we are calculating the mole they giving us the mass concentration that's 4.00 g per pmp and we can calculate the molar mass of sodium hydroxide because they will always give us something like this. Let me indicate they always give us something like this. N A is 23 like their atomic masses 16 hydrogen is what is one and what other thing do we need?

[00:17:45]Oxygen is 16. I've done that. Sulfur they will always give us this. These are constant values. So from here now let's go. Now we can now add that our mole all right is equal to our mass concentration over what? our molar mass.

[00:18:03]All right. What is the mass? Our mass is in the question. They gave us four.

[00:18:10]0 g per dm. Yes or no? Our mar mass, WE CAN CALCULATE the molar mass. Molar mass of N A. We are given already that our Na is 23. Our oxygen is 16. These are constant values you'll be given. So we can have the mar mass of this. So we can have n a = to 23 that's sodium plus oxygen 16 plus hydrogen 1. So our N AO is going to be this is 39. All right.

[00:18:44]Then plus one that's 40 g per mole. Please you are going to be penalized if the units are not correct.

[00:18:53]So the unit you can see for my mass g per dmq for my what? for my mar mass g per mole my mar mass concentration g per mole then I can now use this formula now our mole equals to what is our mass concentration that is 400 g per d mm cq over what's our m mass concentration that's 40 g per mole don't forget g will cancel g did you see that so our mole if I do four divide this that will give us four divide 40 you know this 4.0. So that will give us 0.13 0 mole per dmq.

[00:19:36]I want to believe this is clear. YOU DON'T FORGET if you punch your calculator it will give you 0.1 but most times when we are recording our mole per dmq will do to three significant figure.

[00:19:46]You get that now? So that's why I had to put 0 mole per dmq. So our number one is sorted. Concentration of B in mole per dm cube is sorted. Number two, there's a concentration OF PURE A.

[00:20:00]PLEASE PAY ATTENTION TO THIS. NOW, CONCENTRATION of pure A in mole pad.

[00:20:05]Now, let's jump to the question. They said A is a SOLUTION CONTAINING WHAT?

[00:20:09]IMPURE. LOOK AT THIS. SO, WHICH MEANS THAT ALL THE VALUES GIVEN for A are values for impure acid. DID YOU SEE? SO, IF I USE ANY of these values given, it means that what I will be getting will be the impure. BUT NOW THEY ASK US TO WHAT TO GET THE PURE acid in mole permk which means we are not giving any information here about the pure acid.

[00:20:35]The information we are giving is impure.

[00:20:36]SO I CANNOT EVEN USE any of these INFORMATIONS BECAUSE THE 4 G IN 250 CM cube is for the impure. Did you see now?

[00:20:45]SO WHAT DO I DO THEN? I USE MY formula my titration formula very common formula. C A V A over CB VB equals to N A / N B. Why? Because I'm not giving any information here about the pure acid. No information here about the pure acid. So I have to use this. SO WHAT IS OUR CA?

[00:21:08]THAT'S CONCENTRATION of acid. Can you see that? What are we looking for?

[00:21:11]Concentration of pure acid. A. So I'm looking for C A now. So I do C A times what is our VA? VA means volume of acid.

[00:21:21]That's our average volume of acid.

[00:21:23]Volume of acid Va volume of acid. And what is that? 12.23.

[00:21:30]All right. Over concentration of base CB. What is the concentration of base?

[00:21:37]CB. Don't forget the number one said concentration of B. That's C B. And that's what we have gotten which is what? 0.1.

[00:21:46]So 0.1 0 0 times volume of base. What is the volume of B? That's why they ask us to record it. The volume of pipet because I pipeted 25 which is the volume of the base because what I pipeted is the base. All right. So volume of pipet is 25. So I have 25 equals number of moles of acid. That one will be in the equation. So let's see this is the equation of reaction. Can you see what is the mole of acid here?

[00:22:15]That's one. It's not there. They won't write it. That's one. If you see the base that is two. So our Na that's number of moles of acid is one. One mole of H2S04 to 2 moles of sodium hydroxide.

[00:22:29]So number of acid is one over number of base is two. Number of moles of base. So from there we can cross multiply. All right. We can cross multiply. Don't do this. I'm just doing that. So when we cross multiply what do we have? We going to have that our CA is going to be this 0.10 * what? 25 * 1 over this * this 12.23 * 2 because we are making CA the subject here. So from there what do we do? We have CA equals let's have our calculator.

[00:23:06]Let's have our calculator 0.10 1 0 0 * 25 * 1 what has it giving us? That's giving us 2.5.

[00:23:16]Our CA is 2.5 over 12.23 * 2. That's giving us 24.46.

[00:23:28]So our CA is going to be 2.5ide 24.46 46.

[00:23:36]And that's going to give us 2.5. All right. 2.5 / 24.46.

[00:23:46]2.5 / 24.46.

[00:23:52]That's giving us 0102 approximately to to three to three significant figure. as mole pen key. I want to believe this is clear.

[00:24:06]Please take your time. Take your time for all these questions. You take your time. Please take your time. There is no see one thing you should understand about titration is that they are going to be we are going to be solving from known to unknown. THEY CAN CHANGE THE QUESTION. THEY CAN SAY A IS A SOLUTION of this while B is is impure base. JUST UNDERSTAND WHY WHY AM I NOT USING ANY INFORMATION HERE BECAUSE WHAT THEY ASKING FROM ME IS THE PURE acid and they didn't even mention anything about pure acid here let alone giving me the value so I can't USE ALL THESE ALL THE information here is for impure but they asking me to look for pure so take note of that I want I want to rub some okay let me rub off this place I'll still leave this place let me rub off this these are just the instruction let me rub off Let me rub off this.

[00:25:02]So, let me rub off this. This is the question.

[00:25:07]All right.

[00:25:08]So, what is the next question now? What is the next question? THEY SAID NUMBER THREE. CONCENTRATION of pure A in gram per MQ. Let's come to this place. I want to believe you are seeing this. Let me put this somewhere so that we can. All right. So concentration of what? OF PURE A IN GRAM PER DMQ. DID YOU see that? In g per dmq.

[00:25:33]So we know that FROM HERE. PLEASE REMEMBER this formula. Mole is a lifesaver equal to mass over molar mass.

[00:25:43]Look at that. Now what are WE LOOKING FOR? THEY SAID CONCENTRATION of pure in g per dmq. Meaning we are looking for mass. Did you see? We are looking for mass. Do we have our mole? Yes. That's what we have gotten 0.102. DO WE HAVE OUR MAR MASS? YES, WE CAN CALCULATE mar mass of H2S. So did you see? So if we make this the subject because we are looking for mass. If we make it the subject, it becomes mole* mass. So let's come to this place now to do number three. So we know that our mass is equal to mole* molar mass. So let's calculate the molar mass.

[00:26:24]molar mass of H2S4.

[00:26:28]So that will be equal to we'll be given the atomic masses. Hydrogen is 1 time what? Two. Let me write it some. Let me put that here so that I won't rub up this one. So hydrogen is always one.

[00:26:40]That's the atomic masses. Na is 23. S is 32 and O is 16. They will give us all this. So hydrogen is one. Can you see?

[00:26:49]So 1 * this 2 plus sol for what you solve for 32 plus oxygen. What is oxygen? 16. That's what * 4. So that will be 2 + 32 + 64.

[00:27:06]And that will be what? Let's have 2 + 32 + 64.

[00:27:13]That's giving us 98.

[00:27:16]Don't forget we are looking for what?

[00:27:18]The molar mass. So that will be 98 g per the units are very important. If you don't have those units written your mark will be deducted. So let's come here now. So from that now we can now have our mass to be equal to what is the mole there? You have solved it the 0.102 time what is the mass now? 98. What am I doing? I'm just making this the subject.

[00:27:42]Mass will be mole* molar mass. So the mole is 0.102 102 * the molar mass 98.

[00:27:50]So from there our mass becomes 0.102 * 98. What will it give us? 0.102 that's 9.

[00:28:04]That's 9.996.

[00:28:06]9.996. And that that's just 10.0 0 g per d m cube because I got 9.996.

[00:28:17]Did you get that? If I approximate this now, it's going to give me 10.0 g per dm cube. Did you get that? So, which means that we have solved number three. We have solved number three. Concentration of pure a in g per dmq. We have solved number three. Number four. Now number four.

[00:28:37]Number four. THEY SAID NUMBER OF HYDROGEN aon in 1.0 gm cq OF A. DON'T FORGET WHAT IS A H24.

[00:28:47]So we can write the dissociation reaction of a2s4 that's h24.

[00:28:52]It dissociates to give us 2 hydrogen ion plus4 2 minus. So one mole 1 mole of H2 SO4 is going to give us what? 2 moles of hydrogen ion. Is this clear? Just from the questions just like I have H.

[00:29:15]If you dissociate give me H plus CL. So one mole of this will give one mole of hydrogen A. If I have HNO3, it will break down to give me H+ NO3 minus one mole of HNO3 is going to give me one mole of hydrogen. But if I have A2 SO4 is going to give me two hydrogen AON plus SO4 2 minus because this a diabasic you know this diabasic this monobasic monobasic that's why we have to understand a topic called basicity of acid. Did you get that? I'm just showing you this so that you just trying to review that. So, SO FROM HERE NOW WHAT is the mole of hydrogen that we have before? DON'T FORGET LOOK AT THIS.

[00:30:02]THE HYDROGEN WE HAVE THAT'S WHY THEY SAID IN 1.0 DMQ THE MEANING OF THIS IS THAT we have 0.0.102 mole per dm cq. Did you see that now? So you can now say that one mole I hope you are seeing the board. 1 mo of a2 SO4 is equal to 2 * what is the marity we have there 0102 did you get that now so 1 mole of H2S04 is going to produce 0102 * 2 what will be that 0102 * 2 that's giving us 0.204 0.204 204 moles of hydrogen ion. All right. SO FROM THERE WE NOW UNDERSTAND BECAUSE HE ASK US TO LOOK FOR THE NUMBER OF HYDROGEN.

[00:30:56]Don't forget that one mole all right of hydrogen a will now be equal to 6.02. That's avagadro's constant. One mole of hydrogen aon is 6.02. They they also give us that value.

[00:31:12]They give us somewhere. You do something like this NA if we are going to be asked you give us 6.02 * 10^ 23 to be in the question meaning Aadro's number you SEE THAT SO ONE MOLE OF hydrogen is 6.02 * 10^ 23 aons right so but WE WE WE DON'T HAVE ONE MOLE AGAIN HOW MANY mole we have from the equation and from the reaction is 0.204 so we can now say 0.204 204 moles of hydrogen aon in avocados is going to give what? X. Did you see that?

[00:31:48]One mole of hydrogen. This is a constant 6.02 * 10^ 23 aons. Then 0.204 because we have 0.204 moles of hydrogen there.

[00:31:58]So then we can have cross multiply our X will be 0.204 * 6.02 * 10^ 23. So our X will now be 0.2 204.

[00:32:11]Just multiply this. Don't stress yourself. Just this and this. All right.

[00:32:15]So 0.204 * 6.02.

[00:32:20]And that's going to give us 1 1 is giving me 1.228.

[00:32:26]So to to three significant figure I can just say 1.23 * what? 10 to power 23.

[00:32:37]I want to believe this is clear. Please take note of this. TAKE NOTE OF THIS THERE. THAT'S the reason why we are chemistry hang out. We want to simplify all these things FOR US. SO UNDERSTAND THIS H2S04 we librate two hydrogen ion plus SO42 minus one mole of H2S04 gave two moles of this and from the what we have solved for CA we have 0.102 mole per DMK. All right of the acid. So the 0.102 times the two moles it gave us is giving us 0.20 204 and from a constant value we know that one mole according to Avagadros 1 mole of hydrogen ion is 6.02 * 10^ 23 so 0.204 204 you now give how many that's how I GOT THIS ALL RIGHT so next one our V please take note of these TWO THEY NOW SAID PERCENTAGE purity of tetraosulfate 6 acid percentage purity all right and I I added this so you can be asked for purity or impurity we need to LEARN THAT SO WHAT IS THE FORMULA FOR PURITY SO THAT we know what we are doing so for Let's bring it closer. Percentage purity equals to mass of pure over mass of impure time 100 / one. Since they asking of what? Since they asking of percentage purity. If you not to write the question, please write the question because you know the body is not as big as you know. So that we CAN RUB OFF. NOW MASS OF PURE. NOW GET IT. I WROTE THE FORMULA FIRST so that we can now pick what what are THE VALUES WE NEED. MASS of pure acid. Let's go. THE MASS. LOOK AT IT. MASS OF PURE ACID. WHERE IS IT?

[00:34:31]LOOK at that. The mass. You know this one that they gave us. We have not even used anything here at all. Everything we got was for pure acid. Did you get that?

[00:34:41]The reason is because we will still use it. SO WE WE HAVE NOT EVEN talked about this because everything here is impure.

[00:34:47]So now mass of pure acid is what? Let's write it out. Mass of pure acid is what? 10.0 g per gm. WHAT IS THE MASS OF IMPURE?

[00:35:02]NOW I'M GOING BACK TO THIS NOW. Can you see that? Let's come here now. Let me rub off this. You have sucked this. Let me rub off this. If you need to write it just take the video back so that you can write these things. So mass mass of impure acid. Now what is the mass of impure acid? Now look at this. They said come closer. Now you SEE THEY SAID 4 G in 250. They have given us a clue of the impure. THEY SAID 4 G IN 250. BUT THE STANDARD MEASUREMENT in chemistry is 1 dm cube. Did you see? I cannot use this LIKE THAT BECAUSE THEY SAID in 250 it's supposed to be in 1,00 which is 1,000 cm cube or 1 dm cube. Now look at what I will do. So mass of a pure acid. Now I now say since I have mass of a acid 4.00 g in what? In 250 cm cube. Let me write equal to. So they said we have 4.00 g in what? In 250. SO SINCE THE STANDARD MEASUREMENT is 1,00 cm cube, how many are we going to have? 4.00 G IN 250.

[00:36:16]THAT'S THE information given. BUT THE STANDARD MEASUREMENT is 1,000 cm cube.

[00:36:19]SO IF I HAVE 4 G in 250, how many will be 1,000? I can what? Cross multiply. If I cross multiply, what happens? 250 * x is going to give me 250 x that be equal to 4 * 1,000 that's going to give me 4,000. Is that not I divide both side by 250? I'm just doing all this so that we understand how I'm getting my values. So our s is going to be 4,000ide 250. 4,000 divide 250 that's giving me 16. You can see so that's 16 g per dm. So the MASS OF THE IMPURE ACID IS 16 G PER DMQ. BUT THE MASS OF THE PURE acid is 10 g per dmq.

[00:37:08]So we can now come to our formula now.

[00:37:10]Percentage purity. Percentage purity.

[00:37:15]WE NOW EQUAL TO WHAT is the MASS OF THE PURE ACID? WE HAVE GOTTEN THAT 10. Just write 10 over what is the mass OF THE IMPURE ACID? WE have gotten that 16. All right. Time 100 / 1. So what would that give us? Let's go with our calculator now.

[00:37:36]10 * 100 divide 16.

[00:37:41]That's giving us 62.5%.

[00:37:44]62.5%.

[00:37:47]Look at that. 62. So the the percentage purity that's why I said percentage that's why I'm putting my percentage there. So percentage purity of the sulfate 6 acid is what is 62.5.

[00:38:02]Now then the next one percentage impur I can solve that in two ways as I close.

[00:38:08]So we have solved for percentage purity.

[00:38:10]How do you solve for percentage impurity? So they can ask either purity or impurity. How do we resolve for impurity? I can do percentage of impurity. I'll solve it in two ways. Pick any one that you want.

[00:38:27]Since percentage mathematics student, what is percentage? Percentage means 100. Is that not? So if purity is this, I can add percentage of purity will be 100 minus 62.5%.

[00:38:43]Did you see that?

[00:38:45]BECAUSE THE PURITY IS 62.5 definitely the impurity will be 100 minus this. So percentage of impure is going to be 100 - 62.5 that's 37.5 37.5%.

[00:39:05]I can solve it like this and I think they should mark it for me. But in another way I can do something like this.

[00:39:15]I can do something like this.

[00:39:18]So for our percentage impur we have mass of impurity. All right.

[00:39:26]Over mass of impure acid time 100 over one. Did you get that? So, how do we get the mass of impurity? Now, how do we get the mass of impur?

[00:39:43]How do we get the mass of THE IMPURITY?

[00:39:45]DON'T FORGET THAT THE IMPURE ACID IS 16.

[00:39:48]Look at that. THE IMPURE ACID IS 16. BUT IN THE IMPURE ACID, THEY SAID THE ONE THAT IS PURE here is 10. So, you should be able to get the mass of THE IMPURITY.

[00:39:59]DON'T FORGET THE MASS OF THE IMPURE ACID IS 16. OUT OF THE IMPURE ACID, 10 IS PURE HERE. SO I CAN ADD MASS OF IMPUR will be 16 minus what 16 - 10 16 g - 10 g and that has given us 6 G. WHY MASS of the impure everything the mass of the impure IS 16. OUT OF THAT IMPURE YOU HAVE 10 THERE that are pure. So which means the mass of impur there is what is six g. Then from there we are done. Then we can just do this and we are done. So let's now use this formula now. So percentage impur is going to be mass of the impur now we have gotten that that's 6 over mass of the impure acid mass of impure acid what's that 16 * 100 / 1 so percentage impur so very important too if you are a teacher we already created a group ourel actually it's just like I said earlier in the video is just to you know to actually give professional guidance for us to collaborate for us to network for us to talk about the WK exam and beyond.

[00:41:11]So if you think you're interested in the group, you can just chat to the number on your screen and I'm going to drop if you're not on our WhatsApp channel you not following us on Facebook, you're going to be missing a lot of information. Some people said they don't even know when we upload videos is because you have not been following our WhatsApp channel. We are still going to drop other questions on the WhatsApp channel that we help both both students and teachers. But if you're a teacher, you want to join that our group we call it the teacher strategy group just to share our struggles since we are professional share some of the challenge that we have and we get professional guidance. So what is this 6 * 100 divide 16 that's giving us 37.5% which is the same with this. Did you get that now? So for me if it is w anyway I will prefer this because it's more detailed. You can decide to you know the dot your mark here they might say is not detailed but you can just use this. This is very very detailed and that's it. So that's just what the practical can look like. Don't forget I will drop another video on titration where I will use meti orange to actually titrate. Don't forget I titrated with phenotapine but you know yes I titrated with the phenotapine indicator. I will use material orange again and bring another question so that we can practice they can they can come anywhere is not an exam we need to take like they can come anywhere I'll still drop other predicted question on our WhatsApp channel so that you as a student too can try it give to your teacher to correct you and the rest like that so if you are writing this exam you are a student don't keep this video to yourself don't be selfish share it to your friends their success should be your priority to share it to them like the video subscribe to the channel and I wish you the best in your exam. Thank you so much.