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Offline TPE-luminescence-duby

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Chemiluminescence equation
« on: January 13, 2012, 12:17:07 PM »
Hello everyone !
I am currently running a project in high school in France, where I live, and the topic is chemiluminescence. My group tried to do experiment to produce chemiluminescence with luminol, and it worked ! We used : Distilled water, peroxyde hydrogene, copper sulfate pentahydrate, sodium carbonate, ammonium oxalate, and of course, luminol.
But the problem is, we want to write the equation of the reaction, but we don't know what the products are ! So that's why I'm here, hoping for a little help from awesome scientists  ;)
I have the beginning of the equation, if it can help :
H2O2 + H2O + CuSO4ยท5H2O + Na2CO3 + C2H8N2O4 + C8H7N3O2 => ...
If you could help us, it would be amazing, as this is a huge part of our final grade !
Thank you in advance,
TPE-luminescence-duby

Offline Arkcon

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Re: Chemiluminescence equation
« Reply #1 on: January 13, 2012, 01:20:42 PM »
To help you understand the luminol reaction, try to look up what it means -- why do you need each reactant, what they do, why it won't work without it, etc.  You can track down what are catalysts, and what are simply solvents, and remove them from the equation.  Generally, trying to predict products, just from reactants, is very hard work, and sometimes impossible.  Par example:  http://www.google.com/search?q=M%C3%A9canisme+de+chimiluminescence+du+Luminol&btnG=Search&oe=utf-8&rls=org.mozilla%3Aen-US%3Aofficial&client=firefox-a
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline TPE-luminescence-duby

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Re: Chemiluminescence equation
« Reply #2 on: January 13, 2012, 01:39:04 PM »
Thank you for such a quick answer !
I know that distilled water helps to dilute the other ingredients, sodium carbonate helps the ingredients to mix together, copper sulfate pentahydrate helps the luminol glow, and hydrogen peroxide replaces two of the nitrogen atoms in luminol with oxygen, creating electrons that keep the solution illuminated. And finally the ammonium oxilate helps the solution bright much longer and better.
When we did the experiment, we didn't think of testing the final solution to see what was in it, it was a mistake...
So if I understood the wht was in the link, the hydrogen peroxide is the oxidant, the salts are the activators, and the copper sulfate the catalyst ?



Offline TPE-luminescence-duby

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Re: Chemiluminescence equation
« Reply #3 on: January 25, 2012, 04:49:13 PM »
Am I wrong ?

Offline Jasim

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Re: Chemiluminescence equation
« Reply #4 on: January 26, 2012, 11:29:57 AM »
This is the reaction also on Wikipedia: http://www.angelo.edu/faculty/kboudrea/demos/luminol/luminol.htm

The water is just your solvent, you can ignore it for the reaction.

Luminol + base = de-protonated luminol with excess electrons

Adding peroxide swaps the nitrogens with oxygens (oxidation), in the process nitrogen gas should evolve and excited electrons will lose some energy as light.

Metals are often used as catalysts and that is the case here with the copper sulfate.

The ammonium oxalate is acting as a buffer, allowing the reaction to last longer, it slows it down a bit.

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