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chemical reactions producing oxygen


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#1 lindsay

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Posted 1 March 2009 - 08:33 PM

Hi I am trying to help my 11 year old son, who has aspergers syndrome, with his science homework. He has got to give an example of a reaction which will give off oxygen, a summary of how to test for this & draw & label a diagram of equipment needed. He has done it for hydrogen & carbon dyoxide but is struggling to find info on oxygen. (so am I as I have to type it all up for him & find the pictures to go with it)!
Can anyone help!
Many thanks
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#2 UC

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Posted 2 March 2009 - 08:08 AM

Decomposition of hydrogen peroxide?  2H2O2 -> 2H2O + O2
Decomposition of calcium hypochlorite?  Ca(OCl)2 -> CaCl2 + O2
The way oxygen originally isolated, by decomposition of mercuric oxide?  2HgO -> 2Hg + O2

To test, perhaps the very classic glowing splint experiment? A small piece of wood with an ember will flare up and burn in an oxygen atmosphere.

Edited by UC, 2 March 2009 - 08:51 AM.

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#3 CaptainPanic

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Posted 2 March 2009 - 08:11 AM

Photosynthesis?

When a plant grows, it consumes water and CO2, to produce glucose and oxygen:

6CO2 + 6H2O -> C6H12O6 + 6O2

The reaction has been happening for hundreds of millions of years, and you can investigate it without safety goggles or a fume hood. :D
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#4 big314mp

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Posted 2 March 2009 - 05:05 PM

As for testing it, the quintessential grade school test for oxygen is to take a burning splint of wood and blow it out so that only an ember remains at the end. Stick the burning end of the splint into a container that you think has pure oxygen. If the splint relights (full on flame, not just get brighter), then you have oxygen.

I'm surprised that no one has suggested electrolysis yet. Run an electric current from a battery through salt water, and it will split the water into hydrogen and oxygen. Capture the oxygen in a small tube, then do the above test.
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#5 Mr Skeptic

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Posted 2 March 2009 - 05:50 PM

Edit: nevermind

You could do it the old way, by heat decomposition of mercury oxide. That is one of the first ways oxygen was produced, and I think the first recorded method. However, mercury is poisonous and heating mercury is not the best of classroom ideas.

Edited by Mr Skeptic, 2 March 2009 - 05:57 PM.
nevermind

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#6 hermanntrude

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Posted 2 March 2009 - 10:08 PM

KClO4 -> KCl + 2O2
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#7 UC

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Posted 3 March 2009 - 01:21 AM

KClO4 -> KCl + 2O2


I believe that  2KClO3 -> 2KCl + 3O2 using a bit of  MnO2 as catalyst is going to be easier. It is my understanding that  KClO4 is quite a bit more stable and resistant to decomposition.

As far as I can tell, this is just homework, so dangerous isn't really an issue. If it is actually being done, I suggest adding washing soda and activated carbon to some plain 3% hydrogen peroxide. The bubbles will be  O2 .

As for big314mp's suggestion, that's not quite a reaction to some ears, although it will do as advertised.
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