# Naked Science Forum

## On the Lighter Side => Science Experiments => Topic started by: scientizscht on 31/08/2019 15:05:30

Title: How can I calculate the energy of a battery?
Post by: scientizscht on 31/08/2019 15:05:30
Hello!

If I have two bottles of HCl in different concentrations, how can I create a voltage out of it and how can I calculate the energy generated?

Thanks!
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 31/08/2019 15:09:46
"One can calculate the potential developed by such a cell using the Nernst equation.[1] "
from
https://en.wikipedia.org/wiki/Concentration_cell

But the available energy is tiny.
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 31/08/2019 15:36:00
"One can calculate the potential developed by such a cell using the Nernst equation.[1] "
from
https://en.wikipedia.org/wiki/Concentration_cell

But the available energy is tiny.

Why is it tiny? A human cell is tiny and the concentration gradient is tiny but it is capable of producing 60mV potential.

If you have two buckets of HCl, won't be more?
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 01/09/2019 15:14:35
Also, batteries have energy stored by concentration gradient of lithium ions, why they have more energy than two backets of HCl ?
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 01/09/2019 16:12:18
If you have two buckets of HCl, won't be more?
Yes but more than almost immeasurably small, is still tiny.
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 01/09/2019 16:17:57
batteries have energy stored by concentration gradient of lithium ions
No.
They store energy by changing the oxidation state of the lithium and cobalt (or sometimes iron) they contain.
If you had a cell that used chlorine and hydrogen, you could get a much higher  energy density.
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 01/09/2019 17:07:25
batteries have energy stored by concentration gradient of lithium ions
No.
They store energy by changing the oxidation state of the lithium and cobalt (or sometimes iron) they contain.
If you had a cell that used chlorine and hydrogen, you could get a much higher  energy density.

1) How lithium batteries work?
2) How would a cell use chlorine and hydrogen and why that would have higher energy density?
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 01/09/2019 17:55:14
I really think that finding out how batteries work is
(2) something you should have done before embarking on this thread.

This might help
https://en.wikipedia.org/wiki/Lithium-ion_battery#Electrochemistry

In principle a hydrogen/ chlorine cell can be made in much the same way as a hydrogen/ oxygen cell
https://en.wikipedia.org/wiki/Fuel_cell
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 01/09/2019 20:00:41
Well I have not found any good description. Most have many gaps.

E.g. how Li ions detach from the LiFeO4 electrode during discharge? How they bind to the carbon anode?

Why there needs to be a membrane between electrodes since Li ions are bound to LiFeO4 and upon detaching they flow to the anode and bind to the carbon electrode?

Why there needs to be a carbon electrode to bind the Li ions and not have them floating in the electrolyte?

The whole concept seems to be the move of Li ions between electrodes that bind them. Why do you say there is chemical transformation?
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 01/09/2019 20:06:33
Why do you say there is chemical transformation?
Because there is one
The wiki page gives chemical equations...
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 01/09/2019 22:35:23
No answers to my questions though.
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 02/09/2019 19:38:21
If you do not understand that the presence of a chemical equation shows that a chemical change takes place then you need to start with science 101.
It would be essentially impossible to answer your question without  giving you a grounding in basic science and chemistry.
This forum isn't a good place for that, and we have better things to do.

I suggest you look here
Title: Re: How can I calculate the energy of a battery?
Post by: scientizscht on 02/09/2019 19:59:02
If you do not understand that the presence of a chemical equation shows that a chemical change takes place then you need to start with science 101.
It would be essentially impossible to answer your question without  giving you a grounding in basic science and chemistry.
This forum isn't a good place for that, and we have better things to do.

I suggest you look here

Well I think I know some chemistry more than you. You can depict the dissolution of salt in water as a chemical reaction but it is not really a proper reaction.
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 02/09/2019 20:28:02
Well I think I know some chemistry more than you.
Title: Re: How can I calculate the energy of a battery?
Post by: Bored chemist on 02/09/2019 20:30:41
You can depict the dissolution of salt in water as a chemical reaction but it is not really a proper reaction.
Solid salt does not conduct electricity.
A solution of salt does.
So it is clear that a significant change takes place.
You might not want to call that change "chemical": others might.
It's a matter of semantics, not chemistry.
Title: Re: How can I calculate the energy of a battery?
Post by: jeffreyH on 02/09/2019 21:54:14
Well I think I know some chemistry more than you.