Why H2O2 and Not H20?

  • #1

Main Question or Discussion Point

Why H2O2 and Not H20??

I was wondering under what conditions hydrogen and Oxygen combine to form H2O2 instead of water. The decomposition of H2O2 into water is exothermic, meaning when we seperate the oxygen atom we have less chemical potential energy. The way it was taught to me, less CPE means more 'stability' (whatever that is). My question is...under what conditions will hydrogen and oxygen combine to form a less stable configuration. I know this abstract idea of stability is dependent on local temp. and pressure but I am not sure in what way or why!! Any insights you can offer would be appreciated.

Thanks!
 

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  • #2
Borek
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That's what 99.99% of chemistry is about :smile: We, humans, are particularly unstable combinations of elements, stable version being mixture of water, carbon dioxide, nitrogen and a pinch of inorganic salts...

One of the methods of H2O2 production was electrolytic oxidation of sulfuric acid to peroxydisulfate, followed by hydrolysis. In this case hydrogen peroxide was already more stable than peroxydisulfate solution, in turn hydrogen peroxide decomposition was slow enough so that it could be isolated.
 
  • #3
GCT
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I was wondering under what conditions hydrogen and Oxygen combine to form H2O2 instead of water. The decomposition of H2O2 into water is exothermic, meaning when we seperate the oxygen atom we have less chemical potential energy. The way it was taught to me, less CPE means more 'stability' (whatever that is). My question is...under what conditions will hydrogen and oxygen combine to form a less stable configuration. I know this abstract idea of stability is dependent on local temp. and pressure but I am not sure in what way or why!! Any insights you can offer would be appreciated.

Thanks!
Depends on what you mean by hydrogen and oxygen e.g. hydrogen gas as well as the environment under consideration.

H2O2(aq) + 2H+ + 2e− → 2H2O

The standard electrode potential for this equation is 1.78 V meaning that its favorable with respect to Gibbs as you've mentioned. This formation of hydrogen peroxide can be made more favorable with electrolysis ; I had a potentiometric experiment in the past where this was supposed to have been a culprit in taking up charge at least in my experiment.

Also note that this equation is unfavorable with respect to entropy - this means that a higher temp would favor the hydrogen peroxide. Simply configure the Gibbs equation to understand at what temperature that is.

Other then what was mentioned I would check out the following webpage and perhaps another one which offers more extensive listings to research the different ways that water and hydrogen peroxide can be formed from the different states of hydrogen and oxygen atoms.

http://en.wikipedia.org/wiki/Table_of_standard_electrode_potentials

Hope this helps.
 
  • #4
chemisttree
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I was wondering under what conditions hydrogen and Oxygen combine to form H2O2 instead of water. The decomposition of H2O2 into water is exothermic, meaning when we seperate the oxygen atom we have less chemical potential energy. The way it was taught to me, less CPE means more 'stability' (whatever that is). My question is...under what conditions will hydrogen and oxygen combine to form a less stable configuration. I know this abstract idea of stability is dependent on local temp. and pressure but I am not sure in what way or why!! Any insights you can offer would be appreciated.

Thanks!
That would be the Auto Oxidation Process. In that process, hydrogen is reacted with anthraquinone to produce anthraquinol. This solution is then (in a separate tank) combined with oxygen from air. This liberates the H2O2 which is extracted with water yielding about a 40% H2O2 solution. The other product of the reaction (anthraquinone) is recycled to again be treated with hydrogen to regenerate the anthraquinol.
 

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