MadSci Network: Chemistry

Re: General questions on electrolysis of water

Date: Sun Nov 12 10:14:59 2000
Posted By: Dan Mayer, Post-doc/Fellow, Mathematics and Theoretical and Particle Physics, I am currently out of work.
Area of science: Chemistry
ID: 972162639.Ch

Water electrolyses like this:
2H+ + 2e- ---> H2
2OH-      ---> 2e- + H2O + (1/2)O2

2H2O ---> H2 + (1/2)O2 + H20.

(sorry, but I don't know how to get subscripts and postscripts into e-
A normal battery has a high enough voltage to make this happen, use a 12V 
one if you don't have much patience.
As you can see from the equations, 2 electrons will produce one Hydrogen 
molecule. Faraday's first law of electrolysis states that the mass of a 
substance produced at an electrode is proportional to the electricity 
passed (measured in Coulombs, one electron having a charge of 1.6*10^-19 
Coulombs). This can be seen from the fact that to produce one mole of 
Hydrogen, you need 2 moles of electrons.
Current is Charge per second, so the higher the current, the quicker you 
will produce Hydrogen and Oxygen.

As well as NaCl, anything ionic will undergo electrolysis (because 
electrolysis is the movement of ions towards electrodes). Try other metal 
compounds, such as Copper Sulphate - which will plate the cathode in 
copper. Anything with an electropotential above Hydrogen's (such as Cu 2+, 
and Ag+ ions) will be discharged at the cathode in preference to Hydrogen. 
Anything with an Electropotential more negative than 0.4V (the value for 
O2 + H2O + 4e- ---> 4OH-) will be discharged at the anode in preference to 

Current Queue | Current Queue for Chemistry | Chemistry archives

Try the links in the MadSci Library for more information on Chemistry.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2000. All rights reserved.