batteries

[deleted-29876]

hi there

i have carried an experiment which involves electrolytic cell

i have made the sodium chloride electrolyte to produce electricity itself without the aid of an external voltage.
i have done this simply by adding hydrogen peroxide in the electrolyte as the catalyst. then i have deepen two electrodes copper and magnessium. i have then measured the vlotage of the electrolyte which made 1.7 voltage. i have used it to power 3ohms appliances such as mp3 player, bulb and calculator. the discharge of the cell lasted for 120 min. i have even compared the discharge time with the other type of the batteries which were 1,2v lead, 1.5 eveready, and energizer. it was beat only by lead cell by discharge time.

so i am incapable of balancing the chemical reaction equetion.

[amyC]

Hi - I've moved your post to a topic of its own. By putting it at the end of an older thread, it may or may not have been seen by our experts.

Amy
Science Buddies

[deleted-71588]

Note to amyc, splitting this thread was a bad idea! In order to respond, the experts now have to have both threads open. Previous thread is: https://www.sciencebuddies.org/science- ... php?t=5179

Thabang,
Did you look up the electomotive series? The values for copper (-0.47V) and magnesium (+2.4V) imply that you SHOULD see an open circuit voltage of (+2.4V - (-0.47V)) = 2.87V.

Under what load conditions did you measure 1.7V? If there was a load, then part of the expected 2.87V is appearing across some internal resistance and you are going to have to measure the true open circuit (as close to zero current flow as your meter will allow).

If you did measure this under no-load, then you may not be dealing with pure metals in your electrodes. You either have some significant oxide formed in the metal crystal structure or some other metal co-mingled in the crystal structure.

Amanda gave you the balanced hydrogen peroxide oxidation chemical equation assuming the hydrogen peroxide was reacting (and not just a catalyst as you stated).

Was there any bubbling around either or both electrodes when current was flowing? If there was, then hydrogen (and probably oxygen if bubbles were at both electrodes) were being released and the hydrogen peroxide was being depleted.

There are too many unknowns without more detailed observations and descriptions of your battery, load, circuit, behavior over time and knowledge of the impedance of your volt meter to help you any more.

In the other thread, I gave you hints at the electrical measurements needed to characterize a battery. Have you made any of these measurements?

[deleted-29876]

thanks craig

i have measured the watts of which i had 3.4 watts formula used ( amphour x voltage)

i have simply inserted my two electrodes( on the standard potential table: copper= 0.4 v and magnesium -2,37 ( 0.4-(-2.73)= 2.71 spontaneous reaction) in the solution which i mixed NaCl and H202. the bubbles had quickly occupied the surface of my two electrodes. there after i have put voltmeter on the circuit to measure voltage of the cell without any load on it of which i got 1.7V.

from there i have put 3ohm load on the circuit which lasted for 120 minutes.

i have tried the cell on the variuos temperature to see if it can work and added more of hydrogen peroxide to see if voltage will change but still there weren't any changes.

i have tried this several times just got the same observations.

[deleted-71588]

What is the voltage you measure across the 3 ohm load? This combined with the 1.7v open circuit voltage will help to determine the internal battery impedance.

After 2 hours, were there any visible changes to the electrodes?
If you clean the electrodes and re-insert them into the same solution without any other changes, do you get current flow again and how long does it last?
The answers to these last two questions will help determine whether the depletion is more a function of surface area reactions on the electrodes or depletion of some chemical in the electrolyte.

You state that bubbles form on the surface of the electrodes, but do they escape from the liquid?

I'm still not understanding all of the chemistry involved that yields the 1.7v open circuit voltage. I'm missing some chemical reaction that internally requires about a volt to occur. The bubbles are probably a clue but knowing what gets depleted will be a better clue.