What volume of hyrogen and what volume of oxygen (separately please) would be obtained from the complete electrolysis of one quart of distilled water? How much electrical energy, in Watts would that take. What would be the BTU output obtained form burning this volume of gases together? Water at 70 degrees F, at sea level, final gasses, same conditions.
A quart of water’ll mass 946.3 grams. That’s (946.3/18) 52.57 moles of water, or 52.57 moles Oxygen and 105.1 moles Hydrogen.
That in turn is 26.29 moles O[sub]2[/sub] and 52.57 moles of H[sub]2[/sub].
At 22.4 moles per liter (STP) that much O[sub]2[/sub] will occupy 589 liters while the H[sub]2[/sub] will have a volume of 1178 liters.
It takes about 237.1 kJ/mol to electrolyse water. That’s 65.9 watt hours/mol, or (65.9 X 52.57) 3.46 kwH for your 1 liter sample, at perfect efficiency. At 12 cents a kWh that’ll set you back about 42 cents. Of course “perfect efficiency” is not possible, here are some figures for different methods of hydrogen production.
Burning gaseous hydrogen will give you about 141.86 kJ/g, so your 105 grams of H[sub]2[/sub] should put out 14,895 kJ, or 14,118 BTU. -assuming no math errors
I didn’t check Squink’s link, but the efficiency of the electrolysis stage is going to depend on a lot of factors, such as the voltage that you use and the size and shape of the electrical conductors. In general, you can take the amount of energy it takes to break the chemical bonds, then figure an efficiency factor of somewhere around 50 to 75 percent, with the rest of the energy going into making heat.
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Of course if he insists on using distilled water, you can figure is efficiency will be about 0.1% just from the necessary over voltage. Of course even in a saline solution, the kinetics make electrolysis of water inherently inefficient.
The most energy you can get is the energy you put in to splitting it. Any inefficiency is a loss.
Also there is no such thing as HHO. That’s usually scam language for a simple combination of H2 and O2 often called Browns gas.
The problem with a saline solution is that it doesn’t give you H2 & O2 if the negative or positive ions are gaseous in their un-ionized state. One or the other is replaced by the gaseous ion’s uncharged gas. The other ion in the salt stays in solution, and your aqueous solution becomes the associated acid or base. For example, if you use NaCl as your salt, you get Chlorine gas at one of the electrodes. The solution becomes a NaOH (lye) solution. The Cl2 gas replaces the O2. You don’t want to be releasing that into the environment. I actually did that as a kitchen chemistry experiment when I was in high school. It has been used in the past as an industrial method of producing chlorine, although I doubt it is still in use today, due to the inefficiency of electrolysis.
That depends on what counter ion you use. You don’t have to use sodium chloride. I would use a borate, nitrate or sulfate. If your careful not to use glass, I’ll bet one could use fluoride. I guess some people might interpret saline to mean specifically sodium chloride. That is not what I meant.
You will get oxygen with sodium chloride, but you will also get plenty of chlorine which is not good obviously. You will still get more oxygen with NaCl than you will if you try to electrolyze distilled water.
Yes, you caught me. I was too lazy to pull out my chem references. It’s not quite as simple as I stated. There ARE complications in the solutions that can make a big difference. I used NaCl as an easy example of something I’ve done. Other salts will have the ions still in solutions in other forms. Depends on material’s relative electronegativity, it’s enthalpy relative to the other chemical constituents, their concentration in the solution, etc. I was merely pointing out one confounding situation in water electrolysis that destroys efficiency. I oversimplified it a bit to make it more understandable to non-chemists. We all have are duhhh…BAD. That’s it, BAD days…
Wait a minute. I’m under the impression that distilled water will not conduct a current and that electrolysis is therefore impossible. Can you clarify this? Can it be done with enough electrical force? Is that what you mean by “over voltage”?
Distilled water contains some hydrogen and oxygen ions and will conduct electricity (not well, but it will conduct).
I’m sure Bones404 will be back shortly to thank you all for doing his/her homework.
What about ordinary (non-distilled) tapwater? Are the naturally-occurring impurities enough to make electrolysis possible/practical?