Electrolysis of Water?
Answer:
objective : to determine the ratio of oxygen to hydrogen in water by electrolysis
electrode that you should use is carbon or graphite electrodes
you need to submerge the two gas collecting tubes completely under the water so that you can see the bubbles coming out
water exists in the form of H+ and OH-
OH- will be attrated to the anode (positive)
and will be oxidise(donate electrons) into oxygen
4OH- ----> 2H2O + 4e + O2
H+ will be attrated to the cathode (negative)
and will be reduced(receive electrons) into hydrogen gas
2H+ +2e -----> H2
test for 02 : glowing splint rekindles
test for H2 : burning splint goes off
conclusion :
oxygen : hydrogen = 1 : 2
You could show that the volume of hydrogen gas created is approximately twice that of the volume of oxygen gas created.
This would require determining which electrode generates the H and which generates the O; I can't remember at the moment.
The point is to offer some possbile evidence for the H2O formula of water.
You would also need to make sure that the electrodes were placed in a such a fashion that the gas that eminated from a particular electrode (anode or cathode) would be collected in a tube above the electrode.not drift over into the other gas collection tube. (if much drifting/mixing occured, it would skew your results.)
There are lots of things you will learn on electrolysis of water:
-you will learn how to make electrolytic set-up..
-you will know electrolytic parts like electrode, power source
and electrolyte
-you will know that indeed water is made of 2volume of hydrogen and 1 volume of oxygen.
-sometimes that experiment will proceed to some properties of oxygen and hydrogen like flamibility and support of flamability.
How to make the set-up:
-you will need the following:
* power source like battery or 3 - 12 Volts transformer (extra
care)
* wire
* electrode: the best electrode is platinum but for simple
experiment you can use graphite (rod inside a flashlight
battery) or you can simply use copper wire.
* water, small bottle and container
How to do it:
- connect the wires to the power source, one is in positive
while the other one is in negative.
- connect the electrodes to both ends or simply sand paper
the end of wires to expose themetal
- deep the ends to the container filled with water. (before doing this, turn off the power source to avoid electric shock)
"Done!" you will notice bubbles on ends of wires
- to collect the gas that is generated, (":Warning, turn off the power source before doing this")
fill the two small bottle with water, cover its mouth with your hand, invert the bottle, deep the mouth of the bottle in water and remove your finger as cover. insert the wire ends to the two inverted bottles.
This is termed as water displacement technique to collect gas.
"DOne"
Tips:
-To speed up the generation of gas, you can add small amount of table salt (NaCl) to facilitate conductivity.
(Too much NaCl will generate toxic Cl2 in replace to oxygen so be careful)
Discussion:
- in positive electrode, oxygen is produced ( the one that
supports combustion). Volume is half the amount in
hydrogen.
- in negative electrode, hydrogen is produced ( the one that
is volatile)
- in negative electrode, hydrogen is produced because it attracts the partialy positive charge hydrogen).
2H+ + 2e- = H2
-in positive electrode, partially negative oxygen is attracted.
4OH- = O2 + 2H2O + 4e-
Over all equation : 2H2 + O2 = H2O
Good LUck...
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