# Does the electrolysis of water produce chlorine gas?

http://orbitingfrog.com/2014/11/02/electrolysis-of-water-with-pencils-and-a-9v-battery/

This article seems to indicate that "a small amount of Chlorine may be produced as you [perform electrolysis on water]". Is this true? I thought it was just H2 and O2 produced.

• Water chloration is used to kill some bacteria and microbes in tap water. More info en.wikipedia.org/wiki/Water_chlorination that menas, that chlorine can be produced. – Jaroslav Kotowski Oct 13 '15 at 5:53
• If you use tap or lake water, it will contain a noteable amout of $\ce{NaCl}$ whose chloride ion will be electrolysed to $\ce{Cl2}$. This has nothing to do with water chlorination. (Actually the article says to ‘use a spoonful of salt’, so you’re actively adding more chloride.) – Jan Oct 13 '15 at 8:03
• If you use salt for the electrolyte, you won't get much oxygen... mostly chlorine (and hydrogen at the negative electrode, of course). – DrMoishe Pippik Oct 13 '15 at 21:47