# Hydrogen from water

last night i tried to get hydrogen from water using the aparatus shown.
i have to improve my collection tecnique but i was able to collect about a third of a cup ful ..
say i collect it from the top of a dome shape device .
my question is how will i mix it with the oxygen , to burn it

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second pic.

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russ_watters
Mentor
I can't really tell what I'm looking at there, but if you are doing electrolysis, you are getting oxygen. Since water has both hydrogen and oxygen, splitting it up liberates both (one at the cathode, one at the anode).

iwas wondering wether or not the gas would be mixed , or would it be mostly hydrogen at the top , of the collector?

Q_Goest
Homework Helper
Gold Member
The hydrogen bubbles up from the cathode and oxygen at the anode. The cathode is negatively charged (connected to the minus side of the battery) and the anode is positively charged (connected to the positive side of the battery).

Examine your apparatus and determine which is the anode and which is the cathode. The bubbles that form on those plates are as described above. If those bubbles mix above the water, then you'll have a mixture of oxygen and hydrogen. If you separate them, you will have hydrogen on the one side and oxygen on the other.

Hope that helps.

In its current configuration , i was putting 4.09 V at 2 A into the device..
which is a calculated 2 Ohms ( approx)..
it actually started bubbling at less voltage and current..
Edit : pic 2 ; Is a set of 12 plates alternating copper and zinc , seperated by little pieces of insulators .. top front is the solder connection to the zinc plates ( zinc coated steel)..
bottom front is the connection to the copper plates..
that loop of wire in the very front is just a handle and has no electrical connections

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Ok i've improved the collecter
That H2 , O2 Flame is colorless isnt it ??
It lights with a little pop ..
I wasnt sure it was lit , till i burnt my finger with it..

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$$2H_{2}O \Rightarrow H_2 + 2O_2$$
For safe storage of $H_2$ you might want to collect it seperately from the $O_2$.
Any special reason why you used dissimilar metal electrodes, like you would in a voltaic cell?

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ShawnD
gschjetne said:
Any special reason why you used dissimilar metal electrodes, like you would in a voltaic cell?
Generally you do that so you don't destroy your electrodes. For the cathode (negative), it really doesn't matter what you use because that one stays together. For the anode it makes a huge difference. You're supplying a positive voltage (pull electrons) to a metal, and metals tend to dissolve when they lose electrons. That blue scum in your water is copper (2) something; it's coming from your self destructing copper anode.

Get a carbon anode.

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That's interesting, they never told me in class. Next week I'm doing an electrolysis of copper(II) sulfate, and we're allowed to choose electrodes by ourselves. I should keep that in mind.

Other than that, the cathode material doesn't really affect much, especially electroplating rate-wise?

ShawnD
gschjetne said:
That's interesting, they never told me in class. Next week I'm doing an electrolysis of copper(II) sulfate, and we're allowed to choose electrodes by ourselves. I should keep that in mind.

Other than that, the cathode material doesn't really affect much, especially electroplating rate-wise?
Generally speaking, your cathode should be more inert than the dissolved metal. For example, you can plate chromium or aluminum onto iron, or iron onto copper, or copper onto platinum, but you cannot plate copper onto iron, or iron onto aluminum. Maybe you can, but I haven't found a way to do it.

Has anyone tried electrolysing a mixture of copper(II) sulphate and zinc(II) sulphate? Will that result in a layer of brass on the cathode, or will it somehow act up?

ShawnD
gschjetne said:
Has anyone tried electrolysing a mixture of copper(II) sulphate and zinc(II) sulphate? Will that result in a layer of brass on the cathode, or will it somehow act up?
Brass will not form. Copper that plates onto the cathode will stay there. Zinc that plates onto the cathode will be destroyed by any copper ions in solution; fine chunks of copper will fall to the bottom and zinc will dissolve again.

I have heard that pulsating DC results in electrolysis taking place more rapidly. I tend to think this doesn't make much sense. Does anyone know about the effects of constant input voltage versus pulsating DC on the electrolysis process?

Danger
Gold Member
I've never heard of pulsing DC for electrolysis, but it does bring a different question to mind. If you start with very slow AC, say 1/5Hz, you'd have alternately hydrogen and then oxygen forming on each electrode every 5 seconds. What would happen as you increase the frequency? Is there a point where the molecules just wouldn't separate any longer?

Good question... I was wondering about the effects of AC as well...

Bystander
Homework Helper
Gold Member
Danger said:
I've never heard of pulsing DC for electrolysis, but it does bring a different question to mind. If you start with very slow AC, say 1/5Hz, you'd have alternately hydrogen and then oxygen forming on each electrode every 5 seconds. What would happen as you increase the frequency? Is there a point where the molecules just wouldn't separate any longer?

Longer answer takes more space than post limits allow. If you're curious, do some reading on "electrolyte conductance/conductivity" measurement methods, measurement of dielectric constants, frequency dependence of dielectric constant, Walden product, and that's enough for now. There will be a quiz tomorrow.

What is the best readily available power supply to use to make hydrogen? Taking in mind i don't want to be working with dangerous amounts of current. Another thing is I dont want to short circuit any thing expensive. I was thinking of using a car battery charger; you just plug it into the wall and put the croc clips onto your electrodes. Can anybody give me any reccomendations?

This is my first time at this forum, so I don't know if anyone knows of this site. I have been exp. with hydrogen gen. using pulsating dc. It seems to work fairly well. I'm not sure what the rules are on posting web links, but I would be happy to share the link with anyone intrested.

ShawnD
arthuritus said:
I was thinking of using a car battery charger; you just plug it into the wall and put the croc clips onto your electrodes. Can anybody give me any reccomendations?

Actually I have tried doing that. The result: it destroyed the battery charger.
I saturated the solution with table salt to make sure it had good conductivity. When I connected the battery charger, the gauge said about 4 amps was going through the cell, and bubbles were coming off the electrodes like crazy (I was trying to plate metal, not make hydrogen). I thought that was going good so I left and went shopping. I came back a few hours later to check on my cell and things were not good. To start, the entire garage had a very strong smell to it; it had that smell like when you pour hydrochloric acid on aluminum foil. I think that's the smell of hydrogen but I can't be sure. Secondly, the gauge said there was now 10 amps flowing through the cell; the solution must have made acid or something since hydrogen is one of the few things that would increase conductivity that much. Due to the high current, the solution was literally boiling hot. A few days later, the gator clips for the battery charger were completely rusted, and even after polishing the connectors I could not get a measurable current to flow between the electrodes.

I think the problem was caused by the voltage simply being too high. Electrolysis should be something like 1 volt, but a battery charger is >12 volts (the battery you are charging is rated for 12). On top of that the current was way too high at 4 amps. Even 1 amp is pretty damn high, but this again is caused by the voltage being too high (ohm's law).

If I were to do it again I would probably use a bunch of D size batteries hooked in parallel. That would give 1.5 volts with some pretty high current.

if you set up a circuit with a potentiameter, could you use the gator clips you think?

If you need a spaceheater while you're at it, that shouldn't be a bad idea.
But for the sake of not wasting power, how well would pulse-width modulation work as a means of regulating voltage?

I was bored the other day, so I "dropped" a 1.5 V alkaline cell pried from a 9V battery into a glass of table salt brine. Now it's been sitting there for 2 days, and there are still bubbles coming from the negative electrode. And the glass is filled with lots of flaky brown material, looking like ferrous oxide. Also there is some white crystalline residue on the rim of the glass, what can this be?

Danger
Gold Member
Gschjetne, what has most likely occurred is that the steel can that forms the body of the battery has rusted through. That allows the potassium hydroxide to leak out. That's what the white crystals probably are.

Danger, when I was much younger, and found out about electrolysis, I tried it with a few batteries taped together with just the copper wire tips submerged into some salt water, let it run overnight (so so so hard to not touch it before then haha) and then had a bottle of hydrogen awaiting me. Because I didnt want to wait again, I decided it would be a good idea to cut off the ac plug from a lamp in the garage, not even thinking about the possibility of death, and pluged 'er in. got nothing. I havnt tried again in that way since, but apparently there is a point at which it wont work.

Danger
Gold Member
Ayrity said:
I havnt tried again in that way since
:rofl: Good plan. That's why you can now say 'when I was much younger'.