9.1 The Winkler method (SL)

Understandings:
The Winkler Method can be used to measure biochemical oxygen demand
(BOD), used as a measure of the degree of pollution in a water sample.
Applications and skills:
Application of the Winkler Method to calculate BOD.

[kirstenpaigeperrine]

thirty more minutes til the IB exam and I got it now ty

[acplays]

I have almost covered the entire unit with the help of these videos, however I think you missed the iodine-thiosulfate rxn (titration), it involves iodometry and iodimetry. I was really confused about those. Anyways, thanks a lot:)

[syafiqahamirah]

How to get the ratio of O2 to S2O3^2-?
I still does not understand that step

[sonali.dfernando]

If we take 20ml of the waste water out of 300ml for out calculation, do we divide 2.43mg of o2 by 20ml?

[taeheekim]

I have a question.
I don't understand why we are dividing the mass by the volume to calculate the concentration? I thought C = n /V?

[lu]

I don’t understand how from the ratios you get the 1:4 ratio, do you have to divide them by each other or something?

[anonmela]

At the start you said its BOD = final-initial, but you did initial-final, howcome

[앙-nt]

When did we find the initial concentration of O2? Im just a bit confused on how you found 8.11 for the initial concentration. Otherwise, thank you so much for this helpful video!

[samwilder]

How does the Iodine form in line 2? Is it from the alkaline solution?

[helenaana]

Great video! But I have one question: Why do you calculate the number of moles of thiosulfate if it says *sodium* thiosulfate reacts with the sample in the instructions?

[nicole]

Is the titration of iodine against sodium thiosulfate in the syllabus?

[kellyjin]

Do we need to memorize the Winkler equations for the exam?

[cassandrareilly]

what are the concentrations of each solution?

[shriya]

Thank you so much! Your name should be on my diploma tbh