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+
−
that’s okay). You should hear an 2 H 2O (l) → O 2(g) + 4 H (aq) + 4e
instant pop and see a flash of light.
-
−
If you don’t, light the stick again 4 OH (aq) → O 2(g) + 2 H 2O (l) + 4 e
and try it another time. For some
reason, it rarely works the first Overall reaction:
time but usually does the second 2 H 2O (l) → 2 H 2(g) + O 2(g)
or third.
Note that this reaction creates
What you have done is ripped the twice the amount of hydrogen than
molecules of water apart and then oxygen molecules. If the
crashed them back together. A temperature and pressure for both
water molecule, as you saw before, are the same, you can expect to
is two hydrogen atoms and one get twice the volume of hydrogen
oxygen atom. The electricity to oxygen gas (This relationship
encouraged the oxygen to react between pressure, temperature,
with the copper wire leaving the and volume is the ideal gas law
hydrogen atoms with no oxygen principle).
atom to hang onto. The bubbles
you saw were caused by the newly When you put the match to the
released hydrogen atoms floating test tubes, the energy of the heat
through the test tube in the form causes the hydrogen to react with
of hydrogen gas. Eventually that the oxygen in the air and “POP”,
test tube was part way filled with hydrogen and oxygen combine to
nothing but pure hydrogen gas. form what? That’s right, more
water. You have destroyed and
The chemical equations going on created water! (It’s a very small
during this electrolysis process look amount of water so you probably
like this: won’t see much change in the test
tube.)
A reduction reaction is happening
at the negatively charged cathode. This is the idea behind vehicles
Electrons from the cathode are that run on sunlight and water.
sticking to the hydrogen cations to They use a solar panel (instead of
form hydrogen gas: a 9V battery) to break apart the
hydrogen and oxygen and store
+ −
2 H (aq) + 2e → H 2(g) them in separate tanks, then run
them both back together through a
−
-
2 H 2O (l) + 2e → H 2(g) + 2 OH (aq) fuel cell, which captures the energy
(released when the hydrogen and
oxygen recombine into water) and
The oxidation reaction is occurring turns the car’s motor. Cool, isn’t it?
at the positively charged anode as
oxygen is being generated:
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