Electrolysis of pure water
proceeds slowly because the concentrations of H+ and
ions are too small to carry
an appreciable current. The electrical conductivity can be increased
by adding H2SO4
(an acid) or NaOH (a base),
which produce H+ and HSO4-
ions or Na+ and
Since the ions carry the electrical current, their presence permits
more current to flow through the solution.
Hence more electrons enter and leave the electrolytic cell.
Do not use NaCl
(salt) in your liquid to speed up the experiment.
It will create small amounts of chlorine gas.
We suggest using Epsom salt (magnesium sulfate, MgSO4).
Also note that we recommend 6 volts, although other voltage
can work, the higher the voltage the quicker the reaction).
You may want to
substitute test tubes with graduated cylinders, if you want the
students to record the amount of gas collected.