this video saved my neck .. I wasted hours playing around with various recipes out there but in the end the bucket chemistry approach to the initial steps worked best for me too :)
I have a question, what would happen if the sample solution was not saturated with oxygen? I thought measuring the oxygen already present and then waiting 5 days to measure it again would be suffiecient to see the BOD.
Hi Mr. Thornley. May I ask why we have to increase the pH of the solution before we start adding the sodium thiosulfate? Also why specifically allow the floc to settle to the halfway point of the flask and not all the way?
The 1.45g of sodium thiosuphate came from him measuring it before. The sodiumthiosuphate is made up with water (H20) thats why he states that the solution was made up to 100ml with water.
i just have two question 1) why dont we double the moles from MnO2 (middle eqaution) : 2MnO2(Top Equation) even though that is the relation observed by the mole ratio 2) why is oxygen concentration to 2 sigfigs when we used 3 sigfigs for others
1) it is the actual number of mole that jumps up the sequence of equations. eg C --> D mol 2 X + Y --> 2C mol 1 1 2 There are only 2 moles of C, it doesn't matter where the C appear it must be 2. 2) Probably an oversight on my part.
Dear Mr Thornely, thank you very much for giving us knowledge about quantifying the Dissolved Oxygen in water through Winkler method. However, I wanted to ask if pH affect the concentration of DO?
is it not necessary to let the sample sit for 5 days after reagents added but before titration? I thought that was how you calculated BOD. please help!!!
The above video shows the Winkler Method which allows you to measure the concentration of oxygen in water. BOD measurement uses the Winkler Method to get a value. BOD measurement involves fully oxygenating the solution and waiting 5 days before you do the Winkler Method on it! At 14:10 I explain this more clearly.
Maybe. What if the ppm of O2 does not change much - then what. If the ppm does change a lot - would your explanation be simple (eg there is a water fall). or complex. I think it depends on the river and its environs.
Hi Mr. Thornley. I was trying to do this experiment with all the same chemicals except for the iodide source, where I had access to potassium iodide instead. But when I added both the manganous sulfate and the potassium iodide, they both simply dissolve and do not result in any formation of floc. I am also using pond water. Do you know why this is happening and if there’s any solution for it?
Hi Mr Thornley, I'm using this method as part of my extended essay, but neither myself nor my teachers can find where to buy the alkaline iodide azide pillows, do you know where I can buy them?
Why there is not a calculation of mass of thiosulfate in penthahydrate? 1,45 g of sodium thiosulfate penta hydrate contains only 0,.87g of sodium thiosulfate.... so the calculations has to take that into account or you already recalculated the actual mass od sodium thiosulfate?
If you use pentahydrate you need to use the molar mass of pentahydrate in the calculations. You will end up getting the same concentration of the non-hydrated thiosulphate.
When using a hydrated compound, the attached water molecules contribute water to the solution, potentially diluting the final concentration (if the solvent is water). Therefore, you must account for the contribution of water from the hydrated compound when determining the volume of solvent (water) to add. This article describes the calculations involved in making solutions from hydrated compounds. cshprotocols.cshlp.org/content/2008/5/pdb.ip54.abstract
+Miguel Ignacio Cely Guezguan You have to use stoichiometry, because the coefficient of the S2O32- is 2 and the coefficient of the I2 is 1, you need to divide the mole value of the S2O32- by two in order to get the mole value of I2 as the coefficient are in a ratio of 1:2.
+Janice Wang because the 3 reactions are taking place in one solution. Basically, 2MnO2 in the first reaction is the same amount/concentration as the MnO2 in the second reaction
is the sulfuric acid just to provide the H+ in the second equation? and can KI be used to provide the iodide ions instead of alkali iodide azide? thank you in advance!
+Jesica Sutandi yes of course you can add KI in second step to supply iodide ione. but in that case you have to add NaOH or KOH in 1st step to supply OH ions. i hope u got your answer
can you send me chemistry IA about this. Seems like you enjoyed the experiment so i know you'd enjoy making my amazing IA. This is a one in a life time offer, you either take it in 24 hours or leave it
Generally the oxygen is present in this atmosphere. We inhale this oxygen present in atmosphere and survive. But in case of the crustaceans, they survive in the water by consuming the dissolved oxygen in ... Answer link: howwhywhat.net/cant-inhale-dissolved-oxygen-water/
Yes. In your case you have to first oxygenate the water fully and then wait for 5 days. After the 5 days you use this same procedure of the Winkler Method and you will get your BOD.
In 30 years of doing chemistry I have set myself on fire twice, had 2 classroom evacuations and one explosion. As yet I have not hurt my hands with chemicals. I normally wear gloves for concentrated(5M+) acids only.
You should add a trigger warning for the disturbing video game content at the beginning of the video. It adds no educational value to the video to show that kind of content. Although, the rest of the video was informative the intro was slightly unnecessary.
![R3.2.3 Activity Series [SL IB Chemistry]](http://i.ytimg.com/vi/qAl58m6DHfg/mqdefault.jpg)
![R3.2.3 Activity Series [SL IB Chemistry]](/img/tr.png)
![R3.2.2 How to Balance in Acidic Solution [SL IB Chemistry]](http://i.ytimg.com/vi/-rlKs1FWNHo/mqdefault.jpg)
this video saved my neck .. I wasted hours playing around with various recipes out there but in the end the bucket chemistry approach to the initial steps worked best for me too :)
The intro was cool. Thank you for making this video.
This was so incredibly helpful. Thank you!!
You explained it the best out of everyone
Simply a good choice from you man...you've really ease my burden sir
Awesome video!! Very entertaining as well!
5:53 is sodium thiosulfate inside of the burette?
wow..nice video..thanks alot...
cool teacher!
Awesome....so helpful.
Hi Mr Thornley, thanks for share your knowledge with us. I would like to know what is the concentration of the titrant solution.
+Lucas Figueiredo made
from 6.269g of Na2S2O3.5H2O (Mr = 248.18)
made up to 1.00dm3
I have a question, what would happen if the sample solution was not saturated with oxygen? I thought measuring the oxygen already present and then waiting 5 days to measure it again would be suffiecient to see the BOD.
11:40 why did you not double it? while you doubled it at 11:14? Thanks :)
He halved it both times. Pesky molar ratios
Hi Mr. Thornley. May I ask why we have to increase the pH of the solution before we start adding the sodium thiosulfate? Also why specifically allow the floc to settle to the halfway point of the flask and not all the way?
Alas I do not know the answer to either question, I was following the method that came with the reaction :(
how did you know the amount of manganese to put into the river water? and where did 1.45 g of sodium thiosuphate come from at 10:05 ?
The 1.45g of sodium thiosuphate came from him measuring it before. The sodiumthiosuphate is made up with water (H20) thats why he states that the solution was made up to 100ml with water.
At 10:10 have you not already calculated moles of sodium thiosulfate? I don't undestand why the calculations for moles does not end at that point.
Because you need the concentration of O2 in the water. This moles of O2 is 1/4 of the moles of thiosulphate used.
Thank youuu your calculation did help a lot!
i just have two question
1) why dont we double the moles from MnO2 (middle eqaution) : 2MnO2(Top Equation) even though that is the relation observed by the mole ratio
2) why is oxygen concentration to 2 sigfigs when we used 3 sigfigs for others
1) it is the actual number of mole that jumps up the sequence of equations.
eg
C --> D
mol 2
X + Y --> 2C
mol 1 1 2
There are only 2 moles of C, it doesn't matter where the C appear it must be 2.
2) Probably an oversight on my part.
Dear Mr Thornely, thank you very much for giving us knowledge about quantifying the Dissolved Oxygen in water through Winkler method.
However, I wanted to ask if pH affect the concentration of DO?
it will because i said so
im him so its a valid source
Is there any possible substitution for the alkali-iodide-azide?
pottasuim iodide
great video!
extremely helpful, you didn't wear any protective gloves which is hazardous especially working with sulphuric acid. However great video.
Googles is a must, but the acid was of such a low concentration that washing it off promptly would mean no injury.
@@ibchemvids you said at 4:32 it is concentrated and you also moved a little back ....but okay
nice video buddy!
is it not necessary to let the sample sit for 5 days after reagents added but before titration? I thought that was how you calculated BOD. please help!!!
The above video shows the Winkler Method which allows you to measure the concentration of oxygen in water. BOD measurement uses the Winkler Method to get a value. BOD measurement involves fully oxygenating the solution and waiting 5 days before you do the Winkler Method on it! At 14:10 I explain this more clearly.
that's how you calculate BOD5
Why we add sulphuric acid after settle down precipitate?
I have a question sir usually in Winkler methods we use Mncl2 why this time we used Mnso4?
Both salts will do just fine, since the main purpose of the salt used is to produce the Mn2+ ions that will get oxidized by the dissolved O2.
Add 3:53, what exactly is the precipitate?
If Winkler titrations do come up on the exam, will we be given these equations as part of the question?
Almost certainly.
Hello, sir. I would like to know the conc of the manganese sulfate and alkali-iodide azide.
hi sir! would it be possible to do a 2 by 12 IA using this method to compare the oxygen concentration of river water upstream vs downstream?
Maybe. What if the ppm of O2 does not change much - then what. If the ppm does change a lot - would your explanation be simple (eg there is a water fall). or complex. I think it depends on the river and its environs.
Could I ask how much manganese sulfate powder has to be added in terms of weight? Because it wasnt stated
No sure - sorry. If you want to do the experiment best to buy the "pillows" and follow the instructions that come with them.
Instructions unclear, yellow red gas everywhere
I did not expect the game visuals for lecture
I do the method but the solustion is pink do you know What's the problem ❤
Hi Mr. Thornley. I was trying to do this experiment with all the same chemicals except for the iodide source, where I had access to potassium iodide instead. But when I added both the manganous sulfate and the potassium iodide, they both simply dissolve and do not result in any formation of floc. I am also using pond water. Do you know why this is happening and if there’s any solution for it?
I think KI is the wrong chemical. I used specialised "pillows" of chemicals I have never seen before or since at a school.
Can u tell me the concentration of MnSO4- and Na2S2O3
very educative.
Lol what did you spot at 3:35? Was that a coin?
a penny - genuinely found not planted.
Hi . Very nice video. Question: How conc is the H2SO4?
+TRINILCN I cannot recall - but looking at the video I did not seem to worried. Given it must be 6M or 18M, I would guess 6M - sorry.
+Richard Thornley lol @ not worried. Thanks
Hi Mr Thornley, I'm using this method as part of my extended essay, but neither myself nor my teachers can find where to buy the alkaline iodide azide pillows, do you know where I can buy them?
+Tamara A we recently did this experiment and you can prepare your own alkali-iodide-azide reagent. Try googling it
Is there a substitute for Alkaline iodide azide?
Potassium Iodide with some Potassium Hydroxide
Why there is not a calculation of mass of thiosulfate in penthahydrate? 1,45 g of sodium thiosulfate penta hydrate contains only 0,.87g of sodium thiosulfate.... so the calculations has to take that into account or you already recalculated the actual mass od sodium thiosulfate?
If you use pentahydrate you need to use the molar mass of pentahydrate in the calculations. You will end up getting the same concentration of the non-hydrated thiosulphate.
When using a hydrated compound, the attached water molecules contribute water to the solution, potentially diluting the final concentration (if the solvent is water). Therefore, you must account for the contribution of water from the hydrated compound when determining the volume of solvent (water) to add. This article describes the calculations involved in making solutions from hydrated compounds. cshprotocols.cshlp.org/content/2008/5/pdb.ip54.abstract
You add solvent up to the desired volume. If I need 1dm3 I add enough water to make it up to 1dm3. This is subtly different from adding 1dm3.
Hi Mr. Thornley, I thought that one dm cube equals to one thousand cm cube? In 10:19?
Oh nvm i forgot the .10000dm3 equals to 0.1 dm3 xD
A question as obtained the value of 7.89 x 10 - 5 mol. I appreciate your explanation. Thanks
+Miguel Ignacio Cely Guezguan You have to use stoichiometry, because the coefficient of the S2O32- is 2 and the coefficient of the I2 is 1, you need to divide the mole value of the S2O32- by two in order to get the mole value of I2 as the coefficient are in a ratio of 1:2.
+Leo Ger . Thanks for the explanation (0.000158/2) = 0.000078
well done
The water is 8 degrees celsius, right ?not fahrenheit
Yup
Are you located in New York?
not any more!
Can someone explain why you don't double the value?
+Janice Wang because the 3 reactions are taking place in one solution.
Basically, 2MnO2 in the first reaction is the same amount/concentration as the MnO2 in the second reaction
Which type of reaction is in it?
redox
good use of gary's mod.
I solved my problem towards this titration . thank you very much.
is the sulfuric acid just to provide the H+ in the second equation? and can KI be used to provide the iodide ions instead of alkali iodide azide? thank you in advance!
+Jesica Sutandi sorry no idea! I think the azide is needed since it is so unusual!
+Jesica Sutandi Sulfuric acid worked for me! Just a few drops depending on sample size
+Jesica Sutandi
yes of course you can add KI in second step to supply iodide ione. but in that case you have to add NaOH or KOH in 1st step to supply OH ions.
i hope u got your answer
can you send me chemistry IA about this. Seems like you enjoyed the experiment so i know you'd enjoy making my amazing IA. This is a one in a life time offer, you either take it in 24 hours or leave it
Do your own IA lmao
So helpful! Thank you!
Generally the oxygen is present in this atmosphere. We inhale this oxygen present in atmosphere and survive. But in case of the crustaceans, they survive in the water by consuming the dissolved oxygen in ...
Answer link: howwhywhat.net/cant-inhale-dissolved-oxygen-water/
Can anyone help me with my doubts...
1. Can I use the same procedure for 5days bod procedure ?
Yes. In your case you have to first oxygenate the water fully and then wait for 5 days. After the 5 days you use this same procedure of the Winkler Method and you will get your BOD.
Why do u take volume of H2O as volume of O2?
since the O2 is dissolved in the H2O, the volume is that of the H2O
Using this method, I think I'm going to measure how temperature affects the concentration of oxygen in water for my IA.
Did it work?
YES!!!! I did for my chemistry IA, and I'm currently writing it. Thank you SO!!! MUCH!!!
works!!!
I am doing the same experiment for my IA! However, it is not working. :( The titration does not seem to change the color of the solution.
@@Jumybear Hey, did you finish it?
Is this a half life mod or is this gary's mod
the calculations are confusing me :(
wearing a pair of gloves would be better
In 30 years of doing chemistry I have set myself on fire twice, had 2 classroom evacuations and one explosion. As yet I have not hurt my hands with chemicals. I normally wear gloves for concentrated(5M+) acids only.
lol fair enough
Baja
You should add a trigger warning for the disturbing video game content at the beginning of the video. It adds no educational value to the video to show that kind of content. Although, the rest of the video was informative the intro was slightly unnecessary.
r u joking rn