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Homemade Hydrogen

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: john bunsenburner » Thu Mar 26, 2009 12:20 pm

Hey seeing as this thread is hjacked any way: a question to the maker of this thread and any one else who feels like answering this(but rag because we all know you know the answer ;)):

Why does the aluminium and draincleaner( a strong base either NAOH or KOH) make hydrogen gas? Does this process work with other common metals(iron, copper, zinc, lead, tin, silver) or only with aluminium?

(the answer to the second question might help yo with the first)

Lets see what kind of guesses i get here!
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Unread postAuthor: psycix » Thu Mar 26, 2009 5:06 pm

Redox reaction.

Not all metals will work due to the standard electrode potential. I guess that Mg would work aswell.
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Unread postAuthor: rp181 » Thu Mar 26, 2009 6:38 pm

When aluminum goes in water, a protective layer is formed. The sodium hydroxide prevents the formation of that layer. Its a very simple reaction. 8)
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Unread postAuthor: john bunsenburner » Sat Mar 28, 2009 8:00 am

Well from what I know the following recations occur:

Al2O3+NaOH(aq)-->Al(OH)3(aq)+Na2O
Na2O+H2O-->NaOH
Al+H2O-->Al2O3+H2
(Note these reactions are not balanced)

What happens is that the sodium(or potassium) hydroxide in the draino reacts with the layer of aluminium oxide that forms on it's out side(and which makes it so stable and useful to industry) to form aluminium hydroxide which is soluable in water and sodium oxide which reacts with water to form more sodium hydroxide. The aluminium then reacts with the water and oxidises, it "rips away" the oxygen from the water and the hydrogen is given of.

I find this is a very intresting reaction. And, as the lye is not "used up" you can keep this going for a long time, until all the alminium or water is used up. The reactions are exothermic, the container you do it in may get very hot. Do not do this in a metal container as the lye will corrode the metal.
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Unread postAuthor: JohnnyBOOM » Sat Mar 28, 2009 11:42 am

I thought Aluminum reacted with BOTH HCL and NaOH/KOH to create hydrogen as follows:

Aluminum w/ NaOH:
2Al + 6NaOH → 3H2 + 2Na3AlO3

Aluminum w/ HCl
2Al + 6HCl → 2AlCl3 + 3H2

Anyhow, as mentioned before, electrolysis is probably the cheapest way. If speed of gas creation is important, however, the above reactions will beat the socks off of electrolysis. :)
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Unread postAuthor: john bunsenburner » Sat Mar 28, 2009 11:57 am

Yes that is true BUT aluminium is covered by a thin layer of it's oxide, If aluminium wouldn't be then it would not be as corrosion resistant as it is. From all what i have learnt the reaction mentioned by me is the one that generates most H2 but I have little doubt that your reaction may also take place. Electrolosis is most probably cheeper if you can quickly build a cell and need little Hydrogen, while using lye will(as long as my reactions hold true) be cheeper if you can get alumnium scraps.


Edit: I am not quite sure about the chemical formula you gave do you mean
2Na+3Al+O3
Or
Na2Al3O3


Latter does not exist and the first seems very unlikely....
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Unread postAuthor: JohnnyBOOM » Sat Mar 28, 2009 12:08 pm

john bunsenburner wrote:Edit: I am not quite sure about the chemical formula you gave do you mean
2Na+3Al+O3
Or
Na2Al3O3


Latter does not exist and the first seems very unlikely....


According to Wikipedia, and we know Wikipedia knows everything, that's precisely what happens.

The product is --> 2(Na3 Al O3)

http://en.wikipedia.org/wiki/Sodium_hydroxide
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Unread postAuthor: SEAKING9006 » Sat Mar 28, 2009 12:24 pm

So plain old baking soda works well, eh? I did it before with salt and a 9-volt in one of those medicine cups from a bottle of nyquil (unused). I have nothing else to do, as well as plenty of 9v batteries and battery connectors, and I know how to make a good electrode out of aluminum foil. ( the oxygen side becomes extremely corroded, it's very neat to look at at a light)

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Unread postAuthor: john bunsenburner » Sat Mar 28, 2009 1:03 pm

I am highly doubtful about that reaction, the first two steps of my reaction have to be true, as aluminium is covered by a thin layer of oxide, the last one is the intresting one...

And yes baking soda works for electrolosis but the best is a spoonful of sulfuric acid, it is what is used in labs.
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