General Question

julia999's avatar

Shouldn't H2O be in liquid state after hydrogen and oxygen react?

Asked by julia999 (343points) July 8th, 2009

Hi there!
There’s the following equation in my textbook:
2H2(g) + O2(g)—> 2H2O(g)
Why is water written in gas form? Shouldn’t it become a liquid after hydrogen gas and oxygen gas react?

Thanks in advance!
p.s. could it be a typo?

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3 Answers

julia999's avatar

Never mind, I figured it out:

When hydrogen burns in oxygen it produces water in some form and heat. Now what form would the water take if it were really hot? A gas.

Now, what will the water vapor eventually do? Condense to form liquid water.

So, no, it’s not a typo. Water really does exist in the vapor phase after the reaction. And most of the water really will condense to the liquid phase as it cools.

Deepness's avatar

I think about stuff like this all the time.

LanceVance's avatar

Well. Consider a case with ideal conditions, where no energy/heat can “escape”.

Since we have a synthesis reaction and a reaction where the energy released is greater than the energy consumed (therefore an exothermic reaction), this released energy is consumed by the molecules of water. And as many of you are aware, hydrogen is very reactive and a lot of energy is released when it reacts. On the other hand, water has a very high specific heat and all this energy is used by water to evaporate, while the temperature in the surroundings is lower.

Further on is only a matter what balance will be reached, ie how much heat will the molecules of water give a way (condensing in the process) and how much heat will the molecules of “surroundings” (air, other material) consume and heat up.

So .. considering your question: it depends on the conditions of the reaction. But as soon as the reaction is complete, nearly all water would be in gas form, I suppose, but as time passes, some would condensate and some would remain in gas.

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