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Q & A: burning hydrogen and oxygen

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Most recent answer: 06/25/2012
Oxygen+hydrogen=water. But, do I have to add a 1000 degrees temperature to make it work? Please answer.
- Alex Perry (age 12)
Nassau, NY USA
O2+ 2H2 -> 2H2O will happen very slowly indeed at normal pressures at room temperature. The reason is that the molecules have to go through a high-energy intermediate state on the way to the low-energy form, water. They rarely get enough energy to go through that state. A hot spot (maybe a spark, or a lit match) can give some of them enough energy. Then the energy released when they react can get the next batch going, giving a sustained flame or an explosion.

There are other ways to speed up the reaction even at room temperature. Some catalysts allow the hydrogen and oxygen to combine via lower-energy intermediates. People are studying these catalysts a lot, partly for use in fuel cells which convert the energy released in the reaction to useful forms, and partly for use in cells where other useful energy is used to drive the reverse reaction.

Mike W.

(published on 06/25/2012)

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