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 Posted: Thu Jul 17, 2008 4:27 pm Post subject: cathode in lemon battery |
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We all know you can get a current flowing between dissimilar metals
inserted into a lemon (or potato or vinegar or a beer, etc..), but I
am at a loss to explain why different cathodes would produce different
voltages. The metal its self is not reducing (I'm assuming ions in the
lemon, potato, beer, etc. are), so why would the type of metal serving
as the cathode have any impact of the cell voltage? Should't the
voltage be determined solely by the anode and ions at the cathode site
(which do not change if only lemons is used, for example)? |
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| Posted: Thu Jul 17, 2008 5:55 pm Post subject: Re: cathode in lemon battery |
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Thanks, but it did not answer the question. Perhaps you are nit
understanding my question. Better to ask "what reaction is taking
place when dissimilar metals are placed in a vinegar and connected my
a wire'?
Of course it is a redox reaction, but I'm looking for the reason the
type of metal used as the cathode has an effect on the voltage when ,
it seems, it is NOT reacting at all. |
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Yevgen Barsukov
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| Posted: Thu Jul 17, 2008 6:01 pm Post subject: Re: cathode in lemon battery |
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On Jul 17, 11:27 am, jimlough...@gmail.com wrote:
| Quote: |
We all know you can get a current flowing between dissimilar metals
inserted into a lemon (or potato or vinegar or a beer, etc..), but I
am at a loss to explain why different cathodes would produce different
voltages. The metal its self is not reducing (I'm assuming ions in the
lemon, potato, beer, etc. are), so why would the type of metal serving
as the cathode have any impact of the cell voltage? Should't the
voltage be determined solely by the anode and ions at the cathode site
(which do not change if only lemons is used, for example)?
|
The short answer is - metals of both electrodes will try to reduce H+
into H2 by
givin it an electrone (they don't care you call it anode or cathode).
The competition
between both metals will result in potential difference.
Graphite will introduce no "negative" voltage (unless it is too much
oxidized) because
it practically does not react with H+ / H2 either way.
Gold, Silver, Cu will take electrones from H2 that is evolving on its
surface, which will
add up some more dV to that created by anode (although in tests my
daughter did for
2nd grade science fair, measured difference between Au/Cu/Ag is
negligible compared to differences between different active anodes
such as Ni,Fe,Zn,Mg).
Regards,
Yevgen |
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Marvin
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| Posted: Thu Jul 17, 2008 10:27 pm Post subject: Re: cathode in lemon battery |
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jimloughrie@gmail.com wrote:
| Quote: |
We all know you can get a current flowing between dissimilar metals
inserted into a lemon (or potato or vinegar or a beer, etc..), but I
am at a loss to explain why different cathodes would produce different
voltages. The metal its self is not reducing (I'm assuming ions in the
lemon, potato, beer, etc. are), so why would the type of metal serving
as the cathode have any impact of the cell voltage? Should't the
voltage be determined solely by the anode and ions at the cathode site
(which do not change if only lemons is used, for example)?
|
Read the Wikipedia entry at
http://en.wikipedia.org/wiki/Electrochemistry#Electrochemical_cells
It should answer your question. |
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