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Topic: Help me understand how a Lead Acid Battery works  (Read 2829 times)

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Offline Jmos

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Help me understand how a Lead Acid Battery works
« on: August 22, 2023, 08:25:06 AM »
In researching Lead Acid chemistry there are different sources each teaching it a little differently.

So first off, I have learnt that Sulfuric Acid (H2SO4) dissolves in water to form HSO4- + H+ ions,

then straight after: HSO4- can break up to SO42- and H+, and that the SO42- can re-form back to HSO4-. This break up and re-form constantly repeating so at any given time there are both HSO4- & SO42- ions in the electrolyte. If this is wrong please correct me.

When the two electrodes are placed in the electrolyte, there is a small initial reaction at the negative electrode that builds up some - charge and lead sulfate, the - charge then attracts hydrogen ions that screen the electrode from further lead sulfate forming. So onto my main confusing.

The majority of text describe the reaction simply as:

Pb + SO42-  ------->  PbSO4 + 2e-

yet other sources say:

Pb + HSO4-  ----->  PbSO4 + H+ + 2e-

When considering the above ions (HSO4- & SO42-) constantly changing back and forth in the water. I'm confused as to which of the two equations are right, or if the second longer one is correct at all.
If the second one is also correct, how is the ion attracted to the lead ion? How does that H+ ion drop off?

thanks

Offline Borek

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Re: Help me understand how a Lead Acid Battery works
« Reply #1 on: August 22, 2023, 09:28:56 AM »
This is a system of equilibrium reactions. Process can take several steps. Often it is easier to analyze the total outcome by looking at overall reactions than by looking at separate steps.

So in a way every of these reactions is correct, they just concentrate of different aspects of the process and try to approximate it more or less accurately.
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