Hello All,
My question is;
If you have seperated H2 and O in gaseous form, then combine them at atmos press, what happens?
If combined in the pressence of a heat source what happens?
Thanks in advance,
Randy
russ_watters
Oct8-08, 08:17 PM
Welcome to PF. When you combine hydrogen and oxygen, that's combustion. They burn and the waste product is water. Though the activation energy isn't too high, it does exist, so there must be a heat source present to make it happen. Not all combustion reactions require a heat source (above ambient), though. Rusting metal is basically a very slow combustion reaction.
Borek
Oct9-08, 03:22 AM
No such thing as free O, oxygen is diatomic, just like hydrogen - so it is O2.
JGK
Oct9-08, 08:56 AM
this was an experiment they showed me back in highschool.
A clean paint can was used:
2 holes were cut, one into the base and one into the lid. Hydrogen from a hydrogen generator was piped in via the base until the can was considered full (the H2 supply was shut-off then removed). the gas emerging from the hole in the lid was then ignited.
When the ratio of H2 to O2 reaches 2:1 there was a rather large explosion and the teacher spent the remainder of the lesson retrieving the paint can lid from the ceiling tile it was embedded in.
If you wish to do this experiment, you will need to be vary careful in order to avoid the inevitable lawsuits, accusations of terrorism etc., which will arise from any mishaps.
pacaderm
Oct9-08, 11:30 AM
So i make the assumption that, (2)H2 + 02 ~> (2)H2O + ? + heat.
Also, H2 + O2 at atmos press does not spontaneously combust, an ignition source is required.
And a question, When comparisons are made between gasoline and H2 there is a ratio of one gallon of gas is equal to one litre of H2 in energy, is the litre gaseous or liquid?
PS thanks for the welcome!
Borek
Oct9-08, 11:37 AM
For sure not gaseous.
Somehow I find this comparison hard to believe, but that's just a gut feeling.
chemisttree
Oct9-08, 03:19 PM
Trust your gut feeling!
russ_watters
Oct9-08, 07:38 PM
Wikipedia has combustion energies: http://en.wikipedia.org/wiki/Heat_of_combustion
Hydrogen's combustion enery per unit of mass is a little less than 4x that of gasoline. So that's probably where the '1 gallon of gas = 1 L of H2' came from....of course, whoever made that comparison did not consider that liquid H2 has a specific gravity of .07...
Borek
Oct10-08, 03:10 AM
More or less that's what I expected, I was just too lazy to dig into the real numbers. Thank you for checking :blushing: