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Author Topic: How does penny battery work if it's missing some materials?  (Read 2330 times)

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Glovy

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How does penny battery work if it's missing some materials?
« on: February 05, 2016, 10:50:26 PM »

Hi everyone,

I learned in general chemistry about electrochemical cell that is made of 2 electrodes lying each in a bath of salt solution, connected by a salt bridge.
but on a penny battery which is made of layers of: copper coin separated by cardboard soaked in vinegar and above a tin foil.
So I see that the 2 electrodes are: the copper coin and the tin foil, but where exactly are their 2 separate salt baths and salt bridge?
Here it seems like they are separated by only 1 thing: the vinegar (but what is it? the salt bridge? the salt baths?

Example:


Here the 2 salt baths are the Copper Sulfate Solution and Zinc Sulfate Solution




And here is a penny battery:



Thanks
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billnotgatez

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Re: How does penny battery work if it's missing some materials?
« Reply #1 on: February 05, 2016, 11:58:59 PM »

...
but on a penny battery which is made of layers of: copper coin separated by cardboard soaked in vinegar and above a tin foil.
...

In the examples I have seen
The copper coin is made of zinc coated with copper.
That coin is abraded on one side to expose the zinc.
Cardboard is soaked with a solution of vinegar and salt to create a combination of electrolyte with salt bridge.

The stack is as follows
penny copper side down - zinc side up
soaked cardboard
penny copper side down - zinc side up
soaked cardboard
penny copper side down - zinc side up
soaked cardboard
penny copper side down - zinc side up
soaked cardboard
penny copper side down - zinc side up

So in the second diagram you have
where it says electrolyte
that is where the soaked cardboard is located.
Also the diagram does not exactly show the alternation of zinc and copper as I mentioned
So I am not sure what is happening as compared to examples I have seen.

I have not done this -- I have only read it on line.
« Last Edit: February 06, 2016, 12:25:56 AM by billnotgatez »
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AWK

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Re: How does penny battery work if it's missing some materials?
« Reply #2 on: February 06, 2016, 02:30:43 AM »

Vinegar is a very poor electrolyte.
Cardboard soaked in good electrolyte works as salt bridge in voltaic pile.
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billnotgatez

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Re: How does penny battery work if it's missing some materials?
« Reply #3 on: February 06, 2016, 03:26:44 AM »

Vinegar is a very poor electrolyte.
...

I wonder if that is why they suggest adding the salt in the vinegar.
Actually the example I saw was using lemon juice.

This seems easy to try -- I should attempt it.
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Arkcon

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Re: How does penny battery work if it's missing some materials?
« Reply #4 on: February 06, 2016, 05:33:19 AM »

Answering the question ... salt bridge, salt baths, I'm not completely sure, but I believe the answer is, a little bit of both, and a little bit of neither. 

You seem to be under the impression that the only way to make a battery is with two salt baths and a salt bridge.  But pulling apart a commercial battery will show you that those pieces may not be obviously there.  If you're interested in odd homemade batteries, try this one:

Take a lemon, and push a piece of bent paper clip into it 1/4 inch deep.  Take a piece of copper wire and bury it the same way, separated by a small distance in the fruit.  Touch the two wires to your tongue, and you'll get a tingle and metallic taste.  The fruit is both "salt bath" and salt bridge.  The same with the famous "potato clock" -- two dissimilar metals making enough amps to drive a tiny load.

Try to figure this out for yourself.  You have two dissimilar metals.  There is going to be a re-dox reaction, so the e- can do some work.  See if you can figure out what happens.  Look up other batteries too:  what's the salt bridge in a lead-acid car battery?  Also ook up gravity battery, it has no salt bridge.
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