<P> About five percent of hydrogen gas produced worldwide is created by electrolysis . The majority of this hydrogen produced through electrolysis is a side product in the production of chlorine and caustic soda . This is a prime example of a competing side reaction . </P> <Dl> <Dd> 2NaCl + 2H O → Cl + H + 2NaOH </Dd> </Dl> <Dd> 2NaCl + 2H O → Cl + H + 2NaOH </Dd> <P> The electrolysis of brine, a water / sodium chloride mixture, is only half the electrolysis of water since the chloride ions are oxidized to chlorine rather than water being oxidized to oxygen . Thermodynamically, this would not be expected since the oxidation potential of the chloride ion is less than that of water, but the rate of the chloride reaction is much greater than that of water, causing it to predominate . The hydrogen produced from this process is either burned (converting it back to water), used for the production of specialty chemicals, or various other small - scale applications . </P>

With the use of electricity what was learned about the composition of water