Redox and redox equilibria
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Hi, I've just started my investigation on the rate of reaction between manganate(VII) ions and oxalate (ethanedioate) ions and I've been told that I can only use the colorimeter to work out the rate of reaction if you change the concentration of the oxalate ions. I was wondering how i would do an experiment for changing the concentration of the manganate ions because it says that the colour would be very intense and the colorimeter won't be able to distinguish between the different concentrations?
Ulex says
I think the advice you have been given is accurate. If you reduced the concentration of the manganate(VII) so as to make it detectable by the colorimeter, it would be too dilute to do the oxidation.
Your best bet would be to use a sampling method for this part of the investigation. In this, you withdraw samples, treat each sample with potassium iodide, and titrate the liberated iodine with sodium thiosulphate.
I hope I am not giving away anything by saying that there is a very interesting catalytic phenomenon with this reaction which, if you are not aware of it, will give you some rather unexpected results!
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updated: 08 November 2007
