norweger
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We've all heard the mnemonic PANIC: "Positive Anode, Negative is Cathode."

But does that apply to galvanic cells or electrolytic cells? It has to be invalid in one of them.
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iElvendork
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Depends which way you view it
I've always gone with Cathode is positive as that is where the electrons are drawn to, some people say it's negative as that's the electrons are reacting
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charco
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(Original post by norweger)
We've all heard the mnemonic PANIC: "Positive Anode, Negative is Cathode."

But does that apply to galvanic cells or electrolytic cells? It has to be invalid in one of them.
YOu are correct.

It is better to remember that oxidation always happens at the anode.

Electrolytic cell (eg NaCl):
Cl- - 1e --> Cl
oxidation anode, positive electrode

Voltaic cell (eg Zn/Cu):
Zn --> Zn2+ + 2e
oxidation anode, negative electrode

---------------------------------------------

If you need a mnemonic

oxid A tion
A node
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norweger
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(Original post by iElvendork)
Depends which way you view it
I've always gone with Cathode is positive as that is where the electrons are drawn to, some people say it's negative as that's the electrons are reacting
Is it up to us to choose which is negative and positive?

I've been searching for galvanic cells where the mnemonic "PANIC" holds true, but haven't found a single reliable source saying so.

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charco
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(Original post by norweger)
Is it up to us to choose which is negative and positive?

I've been searching for galvanic cells where the mnemonic "PANIC" holds true, but haven't found a single reliable source saying so.

Image
You clearly have not read my post above!
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norweger
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(Original post by charco)
You clearly have not read my post above!
Yes, I've read your post.

iElvendork made a claim I see from time to time, so I asked what basis there is for such a claim, as "all" the charts of galvanic cells mark the cathode as positive.

As to your post, there's only one thing that puzzles me about it. Normally, in galvanic cells we use a chemical reaction to get electrical energy, and in electrolytic cells we use electrical energy to get a chemical reaction.

So, I would assume that to charge a battery, we'd use a power source and while charging we're to think of the battery as an electrolytic cell. But this is how the charging of a battery is charted. Looks like it's an exception from your mnemonic rule:
"oxid A tion
A node"

Image
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charco
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(Original post by norweger)
Yes, I've read your post.

iElvendork made a claim I see from time to time, so I asked what basis there is for such a claim, as "all" the charts of galvanic cells mark the cathode as positive.

As to your post, there's only one thing that puzzles me about it. Normally, in galvanic cells we use a chemical reaction to get electrical energy, and in electrolytic cells we use electrical energy to get a chemical reaction.

So, I would assume that to charge a battery, we'd use a power source and while charging we're to think of the battery as an electrolytic cell. But this is how the charging of a battery is charted. Looks like it's an exception from your mnemonic rule:
"oxid A tion
A node"

Image
If you use an external power source to recharge a battery you are forcing the spontaneous cell reaction into reverse.

If it is not functioning as a cell (which it is not at that time) then you cannot ascribe labels to the electrodes. It is the external power source which is labelled anode and cathode.

All galvanic (voltaic) cells have a positive cathode and a negative anode, while all electrolytic cells have a negative cathode and a positive anode.

However, in all cases oxidations occurs at the anode.
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