[Borek]

Sorry, I have not noticed you were referring all the time to manganate. That's strange, I have never heard about manganate being used in potentiometric titration, are you sure that's what you are asked/plan to do?

[upsidedown]

Thanks for helping me Borek.

Yes, the plans says:
"One of your experiments should involve a redox titration with potassium manganate (VII)."

The plan also says that I have to used the end-point colour change to explain the redox chemistry in the titration reaction. I know that no indicator is required beacuse it should turn pink/purple from clear, but im unsure how to  explain the redox chemistry in the titration reaction. 

[Borek]

Well, manganate (VII) is just a permanganate.

No need for indicator:

http://www.titrations.info/potentiometric-titration-end-point-detection

Not sure what

explain the redox chemistry in the titration reaction

means, other than what is already obvious from the reaction equation.

[upsidedown]

In my second experiment I will be doing a gas collection, which seems easy enough, just add a metal oxide, messure O₂ released, then work out the conc of H₂O₂.
The only problem is that this will give me different concentration from the first experiment, because all measurements are predictions. Do you know if this is acceptable in plans?

[victoria_kay]

I am also doing this plan... and I'm glad to hear I'm on the right lines because nobody at my college seems to have a clue with what they're doing.

I know that I need to dilute the hydrogen peroxide... but I do not know how. In other titrations I have used a 250cm³ volumetric flask to put 25cm³ of the solution being titrated in and then filled the rest up with distilled water or acid. Is it the same with this titration? Should I use 25cm³ of hydrogen peroxide? And how can I calculate the concentration of potassium permanganate to use?

Any help would be fantastic!

[Borek]

Permanganate commonly used in labs is 0.1M.

Not kowing - approximately - concentration of hydrogen peroxide, it is difficult to calculate dilutions. However, you should take into account optimum volume of titrant used - that is, your samples should contain enough hydrogen peroxide so that when titrating you will be using about 8o-90% of burette volue. That should allow backward calculation of dilution.

[victoria_kay]

Thanks that was helpful

I have another question aswell... I am asked to describe another experiment to determine the concentration of the hydrogen peroxide. I know to do a gas collection of O2 from the catalytic decomposition of hydrogen peroxide. However I am asked to do a calculation before to determine how much hydrogen peroxide I should use in the decomposition. Obviously I have to take the capacity of gas syringe into account but I'm not sure whether to use the fact the hydrogen peroxide is "100-volume" to calculate this or use the equation 2H2O2 -> 2H2O + O2 will it make any difference?

Thanks again

[Borek]

Using 100-volume should give an instant answer.