I'd like to set this whole cathode/anode thing straight once and for all

[doubledoctordoubletrouble]

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electrons ALWAYS flow from anode to cathode
reduction ALWAYS occurs at the cathode
oxidation ALWAYS occurs at the anode

Now here's where I get confused:

is anode positive or negative for a voltaic/galvanic cell?
is cathode positive or negative for an electrolytic cell?

 

[Arteezy]

I think it's easier to realize that galvanic cells involve spontaneous reactions and electrolytic cells are nonspontaneous. Once you realize that, and since electrons ALWAYS flow from anode -> cathode, then it is spontaneous for electrons to go from anode(-) to cathode(+) in galvanic since electrons are naturally attracted to + charges, and it is nonspontaneous for the electrons to go from anode(+) to cathode(-) in electrolytic cells since electrons are being forced to the - charges.

 

[ohkos1]

I think it's easier to realize that galvanic cells involve spontaneous reactions and electrolytic cells are nonspontaneous. Once you realize that, and since electrons ALWAYS flow from anode -> cathode, then it is spontaneous for electrons to go from anode(-) to cathode(+) in galvanic since electrons are naturally attracted to + charges, and it is nonspontaneous for the electrons to go from anode(+) to cathode(-) in electrolytic cells since electrons are being forced to the - charges.

2EZ4RTZ

 

[amy_k]

is anode positive or negative for a voltaic/galvanic cell?
is cathode positive or negative for an electrolytic cell?

Anode is negative for voltaic/galvanic
Anode is positive for electrolytic

Remember that oxidation (loss of electrons) from the solution always occurs at the anode. In a voltaic/galvanic cell this is a spontaneous chemical reaction occurring in the solution around the electrodes. The species around the anode is oxidized and the extra electrons cause a negative charge build up at the anode. Electrons naturally flow from the anode to cathode as Arteezy said, because they are attracted to the positive cathode in the flow of the circuit.

In an electrolytic cell this is a non-spontaneous process. A battery drives a potential difference between the two initially inert electrodes, causing the anode to be positive and the cathode to be negative (*because current flows from positive to negative.... and electrons must flow from anode to cathode in electrochemical cells, we label the positive electrode 'anode' and negative electrode 'cathode' in this case). The electrons are forced to flow from the anode to the cathode by the battery, so negative ions are attracted to the anode and oxidized, the resulting electrons flow from the anode round to the cathode.