0
$\begingroup$

I am trying to two 1.5V battery in series to electrolysis a small bowl of tap water oversaturated with salt. But I can't see any bubble on the part submerged (circled on the photo). Could you guys told me what I am doing wrong here? This is a photo of my battery and electrode. I used my hand to press the wires onto the positive and negative end. enter image description here

$\endgroup$

3 Answers 3

1
$\begingroup$

I think your two batteries are not making a connection in the middle. Try straightening them out.

$\endgroup$
1
$\begingroup$

There are at least two issues, not including the fact pointed out by another poster regarding the connection between your batteries. Hydrogen comes off one electrode and oxygen comes off the other electrode. Both these elements have what is known as an "over-voltage". Your batteries must overcome this over-voltage before electrolysis begins.

3V should be enough voltage to overcome the over-voltage issue, so it would pay to check your battery voltage with a volt meter. In addition, any corrosion on the electrodes (very likely on the oxygen electrode) will also have a voltage drop, so you need to use a metal that doesn't easily oxidize. Note that platinum electrodes are often used in this service.

Using a voltage source that has a higher voltage (e.g., a 12V car battery) should work a lot better than two AA batteries. In addition, it takes a LOT of electricity to make a small amount of hydrogen and oxygen, and two AA batteries just do not have enough material to adequately do the job.

Another issue regards the fact that you are electrolyzing salt water. For this type of electrolysis, you will get sodium hydroxide in the liquid phase, chlorine gas off of one electrode, and hydrogen gas off the other electrode. Chlorine is noxious, so if you get your experiment working, you may want to do it in a well ventilated area. Assuming that you actually wanted hydrogen and oxygen, you need to ionize your water with a small amount of sulfuric acid instead of salt.

$\endgroup$
1
  • 1
    $\begingroup$ When I did this as a kid I used carbon electrodes. Of course back then you could easily get carbon electrodes by just taking apart D-size flashlight batteries. $\endgroup$
    – Hot Licks
    Dec 30, 2018 at 21:48
0
$\begingroup$

By pressing the battery wires against the terminals in the manner shown, you may have short-circuited the + and - battery terminals on the right-hand battery. Get you a 2x AA cell holder, snap the batteries in, and repeat the experiment.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.