[appleseed]

i dont understand why hydrogen and oxygen form during electrolysis
if
oxygen has a charge of 1+ and it gains an electron at the cathode
and OH has a charge of 1-
why doesnt OH gain an electron and OH forms at the anode??

thankyou!!

[tamim83]

When you are performing an electrolysis in aqueous solution, you are also oxidizing and reudcing water via the following reactions. 

Oxidation: 2H₂O --> O₂ + 4H⁺ + 4e-       (Anode)
Reduction: 2H₂O + 2e- --> 2OH- + H₂      (Cathode)

If you multiply the bottom equation by 2 and add the two together you get

H₂O --> H₂ + O₂

In the oxidation reaction, oxygen is oxidized and in the reduction reaction, hydrogen is reduced

[appleseed]

ahh, thankyou tamim83, but theres something i still dont get.
so does it mean that when a current is passed through water, the water does NOT split into OH+ and H- ions ?

[tamim83]

Yes it does.  But the ions recombine quickly to form water again.  If you put a little bit of phenolphthalein in the water and do an electrolysis, you will notice the pink color around the cathode; a sign that OH- is indeed produced.  But as soon as the ions disapate, they find on another in solution and recombine