The reason must people are getting value less than 18.1 is simple most schools are using iron sulphate heptahydrate.. You can't use 5.5g of that and get 18.1 your value will be around 8-10cm³. If you use anhydrous iron sulphate your value will be around 18.0 - 19.0cm3. So use anhydrous not hydrated.. If you want to use hydrated then you will have to increase the mass of hydrated salt measures since hydrated and anhydrous salt of iron sulphate do not have same molar mass. So use what waec specify. Thanks
Very wrong comment. The examination has come and gone and what we maintained held water and was valid. Do you expect WAEC to provide the actual concentrations on the instructions in the question paper? As we stated and also observed in the questions, WAEC did not only alter the concentrations on the question paper but also changed specimen B from anhydrous FeSO4 to iron granules (impure iron metal). Even though it may not matter anymore but there is no how you will titrate with anhydrous FeSO4 and get end point of 16-18 cm3 as you stated above. That is fictious. Don't give values that are not practical. We purposely kept silence on your comment until the exam is over to prove you and others wrong that the actual concentrations and specimen will not appear on the question paper as you speculated. Thanks
@bestsciencebrain Sir, after your rough, why did you start the first titration at 3.40 initial value intead of 3.30 which was the final burette reading gotten in your rough
I adjusted the burette reading from 3.30 to 3.40 cm3 but you can adjust to any level convenient for you. Remember that your readings must agree with your teacher's end point and not the readings used here. Thanks
Go to the laboratory and run the practical and don't make assumptions on theoritical bases. Anhydrous FeSO4 is light green and when dissolved in water gives the colour that you see. Don't neglect the effect of atmospheric oxidation of Fe(II) to Fe(III). We did the best to minimize this effect by carrying out the titration as soon as the FeSO4 solution was prepared rather than keeping it for hours or days. Thanks
Sir, when you calculated the conc. of B g/dm3 you got 1.07g/dm3. But from instruction we know it 5.5g/dm3. This difference is traceable to your end point. So what do you have to say. Thanks
Thanks for your comment. Yes, the mass concentration of FeSO4 is 5.5 g/dm3 but you don't expect WAEC to ask you questions and provide values that will definitely agree with the mass concentration on the instructions. Believe me, that the values that will be provided in the question paper will definitely differ as expected from the instructions. WAEC is tactical. Quite agreed that the end point is low but that does not depict its accuracy. End points in this experiment may differ even in the real practical. Why? This is because teachers are using different concentrations of H2SO4. WAEC did not specify the concentration of H2SO4 to be used, neither did they say that H2SO4 is required but for sure it is required. From analytical point of view, the acid should be moderately concentrated with a molarity of 1 M. From the reaction stoichiometry, you will observe that the number of moles of the acid is high 8H+. 95% of teachers would be using very dilute acids of concentration of 0.1M or even less and this will drag the end point low. Whatever end point you get will be used to assess your students, however I will not subscribe to someone quoting a calculated end point of 18.10 cm3 or thereabout as what he got practically in this Redox Titration. Many gimmicks are happening on TH-cam with people fast forwarding their videos to manipulate end point. WAEC must have already done the practical and know the range at which the end point lies even though whatever you give to your students is right but the point we make here is that, there could be situations that may demand calculation of relative atomic mass of a hidden element and whereby you give your students a fabulous end point, may lead them to calculate negative answers. So, we work from the practical point of view and not what we expect to have from calculations. Thanks
Yes. If your teacher's end point is 14.00, you can use any value + or -1 cm3 of his end point to build your table. So your titre values can be : Rough 14.30 I. 14.00 II. 14.00 III. 14.00 Or Rough 14.20 I. 13.90 II. 13.90 III. 13.90 Or Rough 14.30 I. 14.10 II. 14.10 III. 14.10 Or Rough: 14.30 I. 14.10 II. 14.00 III. 13.90 Let your rough titre be at least 0.30 cm3 above what you have chosen as end point to sound logical. The rough is not always considered to be correct being the first titration you carried out and it is believed that you must have overshot solution A with some drops before realising that the colour had changed. Thanks for your comment
You can start from any convenient value on the burette. You can start a fresh titration with the final of the titration done before it or you can adjust to a convenient level of your own choice.
General information (Attention all) Dear esteemed subscribers (Teachers and students). We observed that there has been a lot of disagreement in the end point value. Let us handle all discussions maturely. End points of titration results may differ due to the following reasons 1. Use of impure samples in the analysis. Most of us unknowingly buy adulterated samples and even expired samples 2. Preparation of solutions with impure water. 3. Error in gravimetric analysis. That is inaccurate weighing of samples 4. Not preparing the anhydrous FeSO4 at the time of the experiment. That is not using freshly prepared FeSO4 to titrate.. 5. Using H2SO4 of different concentrations. 6. Use of hydrated FeSO4 instead of the anhydrous To my dear students, no end point is the final bus stop. Use your class teacher's end point and not my end point or any end point from online or any end point from another school. WAEC recognizes all these discrepancies and judges each student by the end point submitted by the class teacher on the exam day to the supervisor. Your teacher's end point would be packaged with your scripts and used to judge only students from your school. Assuming your teacher did not write the end point from this channel, use his own end point. Whether his end point is as low as 0.10 cm3 or as high as 49.90 cm3, he is correct in this aspect, just follow him. Bestsciencebrain is a team of experts consisting of Chemist, Physcist, Biologist, Mathematicians who are well seasoned teachers, lecturers and examiners. Make sure your end point lies in range of plus or minus 0.10 cm3 of your teacher's end point to score maximum eight marks on the table. For instance if your teacher choose end point of 3.50 cm3, then you can use 3.40, or 3.50 or 3.60 If your teacher choose 10.00, then you can use 9.90, 10.00 or 10.10 cm3 As long as your value is in accordance to the above range as given by your chemistry teacher, then you are good to go However, the solution for qualitative analysis (No 2) remain the same for all schools. Thanks
How can we provide live questions on TH-cam to you before the examination date? Who does that? Are you here to learn or to seek exposition of questions?
Sir I think your correct ooo; I have been getting 10cm3 back to back. Even after using all the required value of kmno4 = 1.58g; Feso4 = 5.5g; H2SO4 = 5ml of 1M H2SO4. I think the theoritical value of 18cm3 cant be the same as practical value in this case. Even if you use hydrated Fe2+ salt, I think its still okay because the redox reaction is between Fe2+ and MnO-
The reason must people are getting value less than 18.1 is simple most schools are using iron sulphate heptahydrate.. You can't use 5.5g of that and get 18.1 your value will be around 8-10cm³. If you use anhydrous iron sulphate your value will be around 18.0 - 19.0cm3. So use anhydrous not hydrated.. If you want to use hydrated then you will have to increase the mass of hydrated salt measures since hydrated and anhydrous salt of iron sulphate do not have same molar mass. So use what waec specify. Thanks
Have you done the practical? I guess you haven't. Anhydrous FeSO4 is light green as crystals (solid) not blue. When you dissolve it in water, you would expect to have a theoritically assumed green colour? But it is not. On exposure of the solution to air, there is instant slight oxidation of Fe2+ to Fe3+ by atmospheric oxygen. Hence the solution was acidified with H2SO4 to avoid the precipitation of Iron (III) hydroxide or dissolve any precipitate of Fe3+. Watch that on acidification, the pale yellow colour turns colourless before titration thus the whole Fe3+ has been eliminated. Thanks
Please it is 3.40, there was a little adjustment I did on the burette after the first titration. The video was pulsed then, that is while you didn't observe it. Thanks
@@bestsciencebrain mixture of iron sulphate and the acid. In my school we heated it and struggled to get the constant pink coloration, and we also used oxalic acid instead
We don't get you at all. All the calculations were done to three significant figures with their correct units. There is no omission or mistake at all. Perhaps, you need to review the video. We even wonder whether this is a mistaken comment. We sure know our work okay.. All the calculations were done to three significant figures with their correct units. Concentrations are not expressed to three decimal places but to three significant figures. We are examiners with years of experience. Please take back this wrong assumption and learn chemistry well or are you mistaken significant figures as decimal places
At the end point, the first sharp pink colour marks the end of the reaction. If your end point gives you a faint pink colour, you had better cross checked the concentration of the H2SO4, you added or the purity of your reagents. If the acid is so dilute, then you are wrong. You need at least a concentration of 1 M
11.00 in the third titration is the initial reading of the burette before the titration started. You can adjust the burette to any convenient level before titrating. However, it is not always good to start from 0.00 not only because of meniscus error but because the permanganate is coloured and you will not be able to note the reading clearly should you start from 0.00
@@MAX_TV99No, there is no approximation in volumetric analysis and I did not. I adjusted the burette by reducing the permanganate level from 10.50 to 11.00 before starting the next titration. This is simply done by bringing the permanganate beaker under the burette, opening the tap and allowing the permanganate from the burette to drop into the beaker until you attain your convenient level. It is always advisable to start the initial from a whole number to prevent errors in reading. In this case, it is not advisable to start your initial from 0.00 because it will be hard for you to note the readings because the permanganate is coloured. If you didn't see me adjust from 10.50 to 11.00, then know that the video was paused in the process to avoid making it lengthy
Says who? Who told you I used hydrated FeSO4. The experiment was carried out using the materials as mentioned in the instructions. I don't falsify or manipulate results to obtain values to suit the assumed calculated titre values.
Besides you make assumptions like a non chemist or rather one that is not seasoned. Are you not even aware that even when you dissolve anhydrous FeSO4 in water to make an aqueous solution, it becomes hydrated FeSO4.7H2O
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The reason must people are getting value less than 18.1 is simple most schools are using iron sulphate heptahydrate.. You can't use 5.5g of that and get 18.1 your value will be around 8-10cm³. If you use anhydrous iron sulphate your value will be around 18.0 - 19.0cm3. So use anhydrous not hydrated.. If you want to use hydrated then you will have to increase the mass of hydrated salt measures since hydrated and anhydrous salt of iron sulphate do not have same molar mass. So use what waec specify. Thanks
Most of the salt available in the market is hydrated.
But what WAEC sent is FeSO4
I used anhydrous Feso4 I got 18.60cm3
Very wrong comment. The examination has come and gone and what we maintained held water and was valid. Do you expect WAEC to provide the actual concentrations on the instructions in the question paper? As we stated and also observed in the questions, WAEC did not only alter the concentrations on the question paper but also changed specimen B from anhydrous FeSO4 to iron granules (impure iron metal). Even though it may not matter anymore but there is no how you will titrate with anhydrous FeSO4 and get end point of 16-18 cm3 as you stated above. That is fictious. Don't give values that are not practical. We purposely kept silence on your comment until the exam is over to prove you and others wrong that the actual concentrations and specimen will not appear on the question paper as you speculated. Thanks
Molarity of 1 M H2SO4 is ideal for the acidification. Though, it could varied due to experimental conditions
@bestsciencebrain
Sir, after your rough, why did you start the first titration at 3.40 initial value intead of 3.30 which was the final burette reading gotten in your rough
I adjusted the burette reading from 3.30 to 3.40 cm3 but you can adjust to any level convenient for you. Remember that your readings must agree with your teacher's end point and not the readings used here. Thanks
What will be the least molarity for dilute H2SO4 to be used for acidification
2M of H2SO4
I wish I could subscribe two times 😊😊😊Thank you again sir
Much appreciated
Th clolor of anhyhdrous iron ii sulfate is like blue green or lets say green in color but what am seein the conical flask here is not
Go to the laboratory and run the practical and don't make assumptions on theoritical bases. Anhydrous FeSO4 is light green and when dissolved in water gives the colour that you see. Don't neglect the effect of atmospheric oxidation of Fe(II) to Fe(III). We did the best to minimize this effect by carrying out the titration as soon as the FeSO4 solution was prepared rather than keeping it for hours or days. Thanks
Sir, when you calculated the conc. of B g/dm3 you got 1.07g/dm3. But from instruction we know it 5.5g/dm3. This difference is traceable to your end point. So what do you have to say. Thanks
Thanks for your comment. Yes, the mass concentration of FeSO4 is 5.5 g/dm3 but you don't expect WAEC to ask you questions and provide values that will definitely agree with the mass concentration on the instructions. Believe me, that the values that will be provided in the question paper will definitely differ as expected from the instructions. WAEC is tactical.
Quite agreed that the end point is low but that does not depict its accuracy. End points in this experiment may differ even in the real practical. Why? This is because teachers are using different concentrations of H2SO4. WAEC did not specify the concentration of H2SO4 to be used, neither did they say that H2SO4 is required but for sure it is required.
From analytical point of view, the acid should be moderately concentrated with a molarity of 1 M. From the reaction stoichiometry, you will observe that the number of moles of the acid is high 8H+. 95% of teachers would be using very dilute acids of concentration of 0.1M or even less and this will drag the end point low. Whatever end point you get will be used to assess your students, however I will not subscribe to someone quoting a calculated end point of 18.10 cm3 or thereabout as what he got practically in this Redox Titration. Many gimmicks are happening on TH-cam with people fast forwarding their videos to manipulate end point. WAEC must have already done the practical and know the range at which the end point lies even though whatever you give to your students is right but the point we make here is that, there could be situations that may demand calculation of relative atomic mass of a hidden element and whereby you give your students a fabulous end point, may lead them to calculate negative answers. So, we work from the practical point of view and not what we expect to have from calculations.
Thanks
WAEC doesn't care about end point as it can be different for different schools. They follow the report from the chemistry teacher.
Assuming that the teacher 's endpoint is14.00 can we manipulate ours to be 13.90 I mean can it be less or must it be high
Yes. If your teacher's end point is 14.00, you can use any value + or -1 cm3 of his end point to build your table.
So your titre values can be : Rough 14.30 I. 14.00 II. 14.00 III. 14.00
Or
Rough 14.20
I. 13.90
II. 13.90
III. 13.90
Or
Rough 14.30
I. 14.10
II. 14.10
III. 14.10
Or
Rough: 14.30
I. 14.10
II. 14.00
III. 13.90
Let your rough titre be at least 0.30 cm3 above what you have chosen as end point to sound logical. The rough is not always considered to be correct being the first titration you carried out and it is believed that you must have overshot solution A with some drops before realising that the colour had changed.
Thanks for your comment
Thank you so much Sir but Sir I have a question. Why didn’t you use your final value in I as your initial value in II and all the rest
You can start from any convenient value on the burette. You can start a fresh titration with the final of the titration done before it or you can adjust to a convenient level of your own choice.
@@bestsciencebrainok sir thank you so much Sir your good work will speak for you 🎉🎉1.3k subscribers already 👍👍👍I’m happy for you sir
Sir my teacher got 18.00,,,,,is it correct and what. Is the expected value to use please
If you are a teacher, it is correct.
General information (Attention all)
Dear esteemed subscribers (Teachers and students).
We observed that there has been a lot of disagreement in the end point value. Let us handle all discussions maturely. End points of titration results may differ due to the following reasons
1. Use of impure samples in the analysis. Most of us unknowingly buy adulterated samples and even expired samples
2. Preparation of solutions with impure water.
3. Error in gravimetric analysis. That is inaccurate weighing of samples
4. Not preparing the anhydrous FeSO4 at the time of the experiment. That is not using freshly prepared FeSO4 to titrate..
5. Using H2SO4 of different concentrations.
6. Use of hydrated FeSO4 instead of the anhydrous
To my dear students, no end point is the final bus stop. Use your class teacher's end point and not my end point or any end point from online or any end point from another school. WAEC recognizes all these discrepancies and judges each student by the end point submitted by the class teacher on the exam day to the supervisor. Your teacher's end point would be packaged with your scripts and used to judge only students from your school. Assuming your teacher did not write the end point from this channel, use his own end point. Whether his end point is as low as 0.10 cm3 or as high as 49.90 cm3, he is correct in this aspect, just follow him.
Bestsciencebrain is a team of experts consisting of Chemist, Physcist, Biologist, Mathematicians who are well seasoned teachers, lecturers and examiners.
Make sure your end point lies in range of plus or minus 0.10 cm3 of your teacher's end point to score maximum eight marks on the table.
For instance if your teacher choose end point of 3.50 cm3, then you can use 3.40, or 3.50 or 3.60
If your teacher choose 10.00, then you can use 9.90, 10.00 or 10.10 cm3
As long as your value is in accordance to the above range as given by your chemistry teacher, then you are good to go
However, the solution for qualitative analysis (No 2) remain the same for all schools. Thanks
Sir is this what is going to come out in our chemistry practical for waec 2024
This is speculated questions. Copy them and study the calculations
@@bestsciencebrain yes or no
Okey thanks
is this exactly the questions that would be set for waec 2024 or is this random question pls i need answers
No oh
How can we provide live questions on TH-cam to you before the examination date? Who does that? Are you here to learn or to seek exposition of questions?
Keep up the good work sir.
Thanks I appreciate
Sir I think your correct ooo; I have been getting 10cm3 back to back. Even after using all the required value of kmno4 = 1.58g; Feso4 = 5.5g; H2SO4 = 5ml of 1M H2SO4.
I think the theoritical value of 18cm3 cant be the same as practical value in this case.
Even if you use hydrated Fe2+ salt, I think its still okay because the redox reaction is between Fe2+ and MnO-
You are correct. Your end point only differs from mine because you are using a more dilute H2SO4 but that doesn't make you wrong
Regards
Please how do you add dilute your H2SO4?
@@bestsciencebrainI
The reason must people are getting value less than 18.1 is simple most schools are using iron sulphate heptahydrate.. You can't use 5.5g of that and get 18.1 your value will be around 8-10cm³. If you use anhydrous iron sulphate your value will be around 18.0 - 19.0cm3. So use anhydrous not hydrated.. If you want to use hydrated then you will have to increase the mass of hydrated salt measures since hydrated and anhydrous salt of iron sulphate do not have same molar mass. So use what waec specify. Thanks
Even if you use anhydrous iron sulphate, you will still get around 10-12 cm3 for the average titre
Thank you very much sir
You are welcome
Why is the solution B yellow instead of blue
Have you done the practical? I guess you haven't. Anhydrous FeSO4 is light green as crystals (solid) not blue. When you dissolve it in water, you would expect to have a theoritically assumed green colour? But it is not. On exposure of the solution to air, there is instant slight oxidation of Fe2+ to Fe3+ by atmospheric oxygen. Hence the solution was acidified with H2SO4 to avoid the precipitation of Iron (III) hydroxide or dissolve any precipitate of Fe3+. Watch that on acidification, the pale yellow colour turns colourless before titration thus the whole Fe3+ has been eliminated. Thanks
Thanks Sir this is really helpful 😅
We appreciate
Sir, your second initial reading is suppose to be 3.30 and not 3.40
Please it is 3.40, there was a little adjustment I did on the burette after the first titration. The video was pulsed then, that is while you didn't observe it. Thanks
Sir, what's the reason for the adjustment?
Sir i observed that you didn't heat the solution as is usually done
Which of the solutions please?
@@bestsciencebrain mixture of iron sulphate and the acid. In my school we heated it and struggled to get the constant pink coloration, and we also used oxalic acid instead
The unit was not stated, the conc in mol per dm³ must be in 3decimal place. You need to work more, know the do and don't in Chemistry practical.
We don't get you at all. All the calculations were done to three significant figures with their correct units. There is no omission or mistake at all. Perhaps, you need to review the video. We even wonder whether this is a mistaken comment. We sure know our work okay.. All the calculations were done to three significant figures with their correct units.
Concentrations are not expressed to three decimal places but to three significant figures. We are examiners with years of experience. Please take back this wrong assumption and learn chemistry well or are you mistaken significant figures as decimal places
The purple color is too thick...you are supposed to have a faint purple
At the end point, the first sharp pink colour marks the end of the reaction. If your end point gives you a faint pink colour, you had better cross checked the concentration of the H2SO4, you added or the purity of your reagents. If the acid is so dilute, then you are wrong. You need at least a concentration of 1 M
I agree with you @valerimack3884 it is supposed to be a faint purple color not thick
Isn't it supposed to be pink
It is pink
Please sir I don't know the way you get 11 in ll
I think he approximated 10.5 to the nearest whole number and recorded in two decimal places...11.00
But Sir why can’t we use the same 10.5 and not 11
11.00 in the third titration is the initial reading of the burette before the titration started. You can adjust the burette to any convenient level before titrating. However, it is not always good to start from 0.00 not only because of meniscus error but because the permanganate is coloured and you will not be able to note the reading clearly should you start from 0.00
@@MAX_TV99No, there is no approximation in volumetric analysis and I did not. I adjusted the burette by reducing the permanganate level from 10.50 to 11.00 before starting the next titration. This is simply done by bringing the permanganate beaker under the burette, opening the tap and allowing the permanganate from the burette to drop into the beaker until you attain your convenient level. It is always advisable to start the initial from a whole number to prevent errors in reading. In this case, it is not advisable to start your initial from 0.00 because it will be hard for you to note the readings because the permanganate is coloured. If you didn't see me adjust from 10.50 to 11.00, then know that the video was paused in the process to avoid making it lengthy
Sir how can i get the question pls
Which questions??
Go to the nearest WAEC office, ask for the zonal coordinator's office and ask him
@@bestsciencebrain i think he /she meant if u could snap nd send the 2024 waec questions
Sir please is this the real practical question?
No. They are speculated questions. Study them
@@bestsciencebrain then y do u diecieve ppl saying it is may /june waec question😏😒
Interesting
Thanks
The values are to low you are suppose to use anhydrous iron Ii not hydrated ....that's why the value is very low like this.
Says who? Who told you I used hydrated FeSO4. The experiment was carried out using the materials as mentioned in the instructions. I don't falsify or manipulate results to obtain values to suit the assumed calculated titre values.
Besides you make assumptions like a non chemist or rather one that is not seasoned. Are you not even aware that even when you dissolve anhydrous FeSO4 in water to make an aqueous solution, it becomes hydrated FeSO4.7H2O
@@bestsciencebrainYes I noticed most youtubers are doing it for this 2024 redox titration 😂😂😂
No body is saying the truth.
Everyone 18cm3😂
@@bestsciencebrain They dont know that the water of crystallization has nothing to do with the redox👍
@@anekartrelaxationfilms6813 Thanks a lot. You are a certified Chemist