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Topic: Unexpected sublimation- iodine gas formation  (Read 1172 times)

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Offline plles

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Unexpected sublimation- iodine gas formation
« on: March 05, 2017, 05:36:46 AM »
Hi everyone! For a school project, I am conducting an experiment investigating the relationship between rate constant and temperature . The reaction I'm using is the iodine clock reaction, hydrogen peroxide variation.
The problem is that seconds after the starch and iodine complex and create a dark solution, a dark pink gas forms. I presumed this is iodine gas so I am now conducting the experiment in a ventilated area of the lab to avoid any irritations but I don't understand why the gas even forms in the first place, especially because the gas forms already at room temperature and its boiling point is about 183°C. Could it be that the concentrations of my reactants are too high? I only calculated them to be in the required ratio so that the thiosulphate is limiting, but I had not considered that perhaps they are too high.. although most solutions are either 0.01 or 0.02 M. Any help as to why the gas is forming is greatly appreciated!

Offline AWK

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Re: Unexpected sublimation- iodine gas formation
« Reply #1 on: March 05, 2017, 06:33:36 AM »
Besides concentrations, I think you may used glass that contained some amount of compound which catalytically decomposed hydrogen peroxide and evolved oxygen took some iodine analogously to steam distillation.
AWK

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