Hydrogen Generator Experiment

[evolutionmovement]

Aren't some of the problems with hydrogen that it needs to be stored under great pressure in order to have an appreciable amount and that the molecules are so small they leak through almost everything when not used right away?

[noeryan]

That brings up something I hadn't really thought of... a leakage issue. I believe metal could hold it back, being a crystalline structure. I'm just guessing but I would believe it would hold. I don't believe you would have to have it at a high pressure. Good thought though EVO. I wouldn't worry so much about pressure unless you have a tiny tank. But I'm not exactly sure how much H2 is needed for gains. I'm also not sure how much PV's, tanks, or any other objects needed for the production would weigh. My guess would be about 50 lbs total?

[evolutionmovement]

Metal is permeable to air in tires. Alloy wheels loose air through the metal (supposedly, though I've never actually observed the phenomenon myself—car parked for 4 years still has some air in tires). One of the big obstacles of hydrogen as a fuel is having to store it in pressurized containers to get range out of it, unless that guy who claims to have come up with a way to store it in metal (aluminum foam?) is legit.

[dcb]

Originally Posted by elhigh

Are you sure about that? When my brother and I cobbled together an electrolyzer out of a big aluminum pan, some wiring and a couple of Mason jars, it was the hydrogen that filled up first.

Granted that was about 30 years ago, so some of the laws of chemistry may have been repealed.

I'm a bit rusty at this stuff, but I come up with a figure of about 11.2 liters per mole for 02 and 1.12 liters per mole for H. Since you have 2xH in H2O, you should have about 5x the volume of oxygen as you do Hydrogen.

Based on wikipedia values for atomic weight and density.


But then you read stuff like "one mole of dry gas at STP occupies 22.4 liters" so the hydrogen in H2O would take up twice the volume after electrolysis? I'm struggling to see how such a convenient conversion factor is even possible though.

[noeryan]

TO HELP W/ THE DEBATE ON HYDROGEN/OXYGEN PRODUCTION DURING ELECTROLYSIS:


This is what my Thermodynamics Book says (Fundementals of Engineering Thermodynamics):

There are 2.016 kg/kmol of H2

32.00 kg/kmol of O2

Wikipedia - Hydrogen @ 0 degrees Celcius (32 degrees F) & 1 atm

H2 - 0.08988 g/L or 0.00008988 kg/L

Wikipedia - Oxygen @ 0 degrees Celcius (32 degrees F) & 1 atm

O2 - 1.429 g/L or 0.001428 kg/L


or

H2 - 11126 L/kg

O2 - 700 L/kg


Since there are 2kmol of H2 per kmol of O2:

4.032 kg H2

32.00 kg O2

in 36.032 kg H2O

Multiplying through:

44860 L of H2

22400 L of O2

Determining the ratio:

44860/(44860+22400) = .667 = 66.7% Hydrogen

100% - 66.7% = 33.3% Oxygen


TO CONCLUDE: There should be 2x as much gaseous Hydrogen after electrolysis than Oxygen.

If my math is faulted please correct me.

[dcb]

nope, apparently there are 22.4 liters of molecules (not atoms) per mole for <insert gas here>. So everything gaseous can be compared by volume/percentage for stoic purposes.

[Christ]

Math, simplified:

H20 = H+H+O.

There are 3 total molecules, which make up 100% of the mass.

100/3 = 33.333%

2 of those molecules are H, while one is O.

Since each molecule is 33.333%,

33.333% * 2=66.666%,
and 33.333% * 1=33.333%

Therefore, 2H = 66.666% of the mass, while O = 33.333%.

[dcb]

not mass, number of molecules and volume

[noeryan]

So my method doesn't satisfy you? All of my calculations were based on the molecular elements of H and O (H2, O2)

Where is the miscommunication?

A Mole is a particular number (6.022 × 10^23) . It is a count. It is not mass.

A mole is 602,200,000,000,000,000,000,000.

Therefore when stated that H2 has a mass of 2.016 kg/kmol, it means that 6.022 x 10^26 molecules of H2 has a mass of 2.016 kg.

A mole of H2O has 1 mole of H2 and .5 mole of O2
OR
To simplify it slightly but would not be found in nature... a mole of H20 has 1 mole of H2 and 1 mole of O

Since O is found as O2 in nature you assume the 6.022 x 10^23 O atoms bond together to form 3.011 x 10^23 molecules of O2. This is only half of a mol so to form a whole mol of O2 you need two mols of H2O. If you have 2 mol of H2O, then you have 2 mol of H2.

So 2 mol of H2 and 1 mol of O2 are formed from 2 mol of H2O.

Since these are just numbers the ratio of 2 mol H2 : 1 mol O2 is the same ratio as 2 kmol H2 : 1 kmol O2.

From Wikipedia - Water
H2O = 18.0153 g/mol or 18.0153 kg/kmol



Comparing this number to my previous calculations:

1 kmol of H2O = 18.0153 kg

2 kmol of H2O = 2*18.0153 = 36.0306 kg

Out of this, 4.032 kg is H2 and 32 kg is O2. THIS IS MASS. THIS IS NOT DENSITY.

DENSITY IS MASS PER VOLUME.

Wikipedia also gave a density of each of these elements H2 and O2 in grams/liter.

I inverted this to liter/kg by multiplying the gram/liter*1000 to kg/liter then divided 1 by that number.

Now that you have liter per kilogram, I multiplied it by how many kilograms we have to give liters.

Then determined the total percentages for each H2 and O2.



THE MATH IS SIMPLE BUT NOT AS SIMPLE AS 'CHRIST' DECLARES.

[dcb]

I meant "nope" as in "I don't see a problem with your figuring".

Originally Posted by Christ

Therefore, 2H = 66.666% of the mass, while O = 33.333%.

I think "mass" was a typo here.

And the math is painfully simple if you know the 22.4 l/mole gas law (and that the molecular structures are h2 and o2, and of course h2o)