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volume of water from a litre of hydrogen? Answered

Im no chemist but I am interested in what volume in litres of water would be produced from 1 litre of liquid hydrogen if burnt in air.

Of course it would evaperate and be disspersed but would be 8 litres? 

2h2 + O2 = 2h2O I believe the chemical formular



Best Answer 6 years ago

1 litre of liquid hydrogen is 67.8 grams
molar mass liquid hydrogen (H2) is 2.02g/mol
1 litre of liquid hydrogen is 33.564 mols

2H2 + O2 = 2H2O

33.564 mols of molecular hydrogen will make 33.564 mols of molecular Water...

molar mass of water is 18.01528 g/mol

33.564mol * 18.01528g/mol = 604.6713 grams

So...I was wrong in my other comment to The Skinnerz...a litre of liquid hydrogen will make ~605 mL of liquid...
Given the energy output of the combusion, it will probably be gas, which will be huge volume as steam goes.

Thanks folks This is really usefull I had antisipated the weight gain to be aproxamatly 10 times after seeing the atomic weights, but im suprised the volume of water is less than the volume of hydrogen it doesnt seem logical. This does answer my question though, I will have to reflect on the logic.

Yeah, it caught me off guard too -- I was SURE it would be 'physically' bigger therefore physically larger, but density plays a HUGE role it seems...

At atmospheric pressure, 1L of H2 gas is 1/24 of a mole, which forms 0.75g of water, which at atmospheric pressure is 0.75mL.Though as Steve says, a litre at higher pressure contains more hydrogen, so will make more water.

not sure if the question was edited but it states liquid hydrogen, which would change the output significantly...just take your result

...by the factor of density of gas (satp) and liquid

Unless I've missed something, 1L of liquid H2 will produce 610.2mL of water, going by a density of 67.8g/L for liquid H2.

uhm...1L of hydrogen should make MORE water when you add the other litres of oxygen...should it not?

The Skinnerz is right. You have to count atoms, not volume, unless you do everything in gas phase where the two are proportional. Water is sufficiently more dense than liquid hydrogen that you get a smaller volume of product than of reactants.

right, I did the calculation myself because I couldn't believe it -- its posted as a root comment.

Going by the data on the wikipedia page, liquid H2 has a density under 7% that of water at RTP, while 1g of H2 only forms 9g of water, so it makes sense that the volume of water produced is less. Also, H2 is very light, while water is unusually heavy.

yes i did make a point of the liquid hydrogen and assume liquid water

one would assume the volume of water would be greater than the volume of liquid Hydrogen

But if 1g oh hydrogen makes 9g of water that is usfull

seems reasonable as you need twice the amount of hydrogen as oxygen and water is 18, oxygen being 16 hydrogen being 1

Yes, that's exactly the right logic. You have to use molar quantities (that is, counting atoms), not volumes of liquid. For gases, the ideal gas law (PV = nRT) means that volume and molar quantity are proportional at fixed temperature and pressure, but that's not true for either liquids or solids.