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topic 17745

Water electrolysis project


I am working on a water electrolysis project, and I need some information. How much hydrogen and oxygen are in a cubic meter of water. How many watts are required to convert this much water. After the hydrogen and oxygen are re-combusted how much water is there? how many btu's in this much hydrogen and oxygen.

John R
- Sudbury, Ontario, Canada


John, our readers are usually more than willing to help students with their science projects, but we try to balance this with the pleas from teachers who ask us to please just tell the students to do their own homework.

All of the calculations will be worked from the weight (or mass) of the water. So, first, what is the weight or mass of that volume of water? What is the molecular formula for water? What are the atomic masses of hydrogen, oxygen, and water? Getting closer to an answer for your first question?

Your second question is the hard one. If you were provided with the factors you needed, how would you begin to approach it? I'd start with Faraday's Law.

If you don't know the answer to your third question, that is, if you've never heard of the law of conservation of mass, you don't belong in high school chemistry yet. Return to general science :-)

The fourth question is simply a matter of applying a conversion factor right? So what conversion factor are you looking for? I'll be happy to give it to you. Good luck.

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


I am actually performing electrolysis on salt water for my science fair demonstration. I have removed graphite rods from a battery, secured them to a lantern battery and then inserted them into saltwater covered with test tubes filled with water. I get hydrogen, no problem, but oxygen is proving tough.

The first time I had real erosion problems and the water turned blue. So, I removed the copper wiring attaching the graphite rod to the positive batter cable and changed to a "silver" wire. Now, I am getting a white, milky substance instead of oxygen. What am I doing wrong?

John Carlton P.
Jr. High Student - Sparta, NJ

June 15, 2009

while performing electrolysis of water by adding sulfuric acid in it and using graphite electrodes it was seen that at anode black powder sort of material was precipitated and at cathode maroonish coloured layer formed on graphite rod!
what is the black substance? is it carbon? can I titrate the solution?
and what is the maroon layer and by what machanism it is fromed?

Shashwat Sharma
hobbyist - Indore, MP, India

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