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Can we produce condensed water in a rigid small sphere,where H2 and O2 are present at very high pressure provided that some electric sparks are produced in the sphere by some mechanism? If I would break the sphere, would I find water in it?
Question Date: 2013-01-26
Answer 1:

I think I understand your questions, but forgive me if I missed something. The formation of H2O from H2 and O2
(2H2 + O2 -> 2H2O + heat)
is a canonical example of a combustion reaction. The reaction energy is too high for a simple mixture of H2 and O2 to render H2O, so we need a catalyst, a source of energy for the reaction. A flame or a spark fits the bill. In a rigid sphere filled with H2 and O2, a spark would produce an explosion (a fast release of heat and light) and H2O vapor in the sphere, along with the excess of hydrogen or oxygen. The water vapor may condense to liquid water, but only if the temperature and pressure inside the sphere is below the critical temperature and at high enough of a pressure, respectively. The critical temperature is the temperature above which the liquid phase cannot exist, no matter what the pressure. For water this temperature is at 705 degrees Fahrenheit.

Were you to break the sphere, you would still find liquid water. Even though the pressure would decrease, the temperature would decrease as well. Depending on how dry the air was, it would take a noticeable amount of time for the liquid water to vaporize.

Answer 2:

Absolutely. In fact, even if you just fill a balloon with H2 and O2 gas, then light it on fire with a match, H2O will be produced.

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