Sciencemadness Discussion Board

energy density of water

liljoe086 - 13-6-2007 at 07:28

You see many people tring to figure out how to use hydrogen as an alternative means of power. They talk about the energy density of hydrogen vs gasoline. I would like to know the energy density of 1 gal of water if the water was completely electrolysed (dont care about the energy required to do it).

Nerro - 13-6-2007 at 08:07

Quote:
Originally posted by liljoe086
You see many people tring to figure out how to use hydrogen as an alternative means of power. They talk about the energy density of hydrogen vs gasoline. I would like to know the energy density of 1 gal of water if the water was completely electrolysed (dont care about the energy required to do it).

That seems to be the general problem :P

2/18 of H2O's mass is hydrogen so complete electrolysis would yield 111.11g of hydrogen and 888.9g of oxygen. Which I estimate to have a volume of 1235L when gaseous at RTP (the hydrogen that is. I have no idea about the oxygen.)

With an energy of combustion of 141.9 MJ/kg that means that the combustion of this hydrogen using the oxygen we also liberated we'd be releasing 15.77 MJ.

[Edited on 13-6-2007 by Nerro]

Maya - 13-6-2007 at 14:25

yes but he said density , it would be 15.77 Megajoules per Kilogram

whereas he is asking per gallon, correct?

12AX7 - 13-6-2007 at 18:24

Well then, 1 gal = 3.78 l = kg H2O. Simple enough to figure out from there.

Tim

Nerro - 14-6-2007 at 00:46

If he can't do it from there he shouldn't be allowed outside the house without supervision...

liljoe086 - 14-6-2007 at 08:07

Quote:
Originally posted by Nerro
If he can't do it from there he shouldn't be allowed outside the house without supervision...


They usually dont cuz they know Ill take the world by storm :D