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Author: Subject: Equilibrium of chromate and dichromate
woelen
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[*] posted on 26-5-2019 at 10:30
Equilibrium of chromate and dichromate

I did an experiment with chromate and dichromate, in which a nice equilibrium reaction is demonstrated, which depends on temperature reversibly. One could ampoule this system, so that no compounds are lost or gained and then use that ampoule to show the equilibrium (yellow when cold, deep orange when hot).

I wrote a web page about it:

http://woelen.homescience.net/science/chem/exps/chromate_dic...



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RedDwarf
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[*] posted on 26-5-2019 at 11:33


Do you know what the mechanism is that pushes the equilibrium to the right at higher temperatures?
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[*] posted on 26-5-2019 at 12:10


If a reaction is endothermic, then increasing the temperature will increase the equilibrium constant.



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[*] posted on 26-5-2019 at 14:10


Thanks woelen. I like the idea of sealed ampoules for this. I think I will make some to add to my teaching kit.
J.



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[*] posted on 26-5-2019 at 21:14


Interesting experiment. I suppose that buffer consumes OH- from hydrolysis of chromate is that right?
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woelen
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[*] posted on 26-5-2019 at 22:39


Yes, the chromate condenses to dichromate and this produces OH(-), which is neutralized by H(+) ions. If these H(+) are not present, then the chromate only forms a little amount of OH(-) and the condensation reaction stops.



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