Anode and Cathode - Positive or Negative

[ipmed]

When is an Anode negative, and a Cathode positive, and why are they like this in a spontanous cell or discharging cell.

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[brood910]

Anions flow to anodes not because of charge attraction to anodes. Electrons flow from anode to cathode so anions move to anode to keep the charge balanced.

 

[Oso]

anode = oxidation
cathode = reduction

In a galvanic cell, the electrons spontaneously flow from the anode to the cathode, so the anode is the negative terminal and the cathode is the positive terminal. To reduce the build up of charge, anions from the salt bridge flow to the anode, and cations flow to the cathode.

In an electrolytic cell, the anode is the positive terminal and the cathode is the negative terminal. Electrons still flow from anode to cathode, but they're being forced to do so (non-spontaneous) by a battery. Salt bridge is the same.

 

[ipmed]

thanks

 

[O-Block Uchiha]

anode = oxidation
cathode = reduction

In a galvanic cell, the electrons spontaneously flow from the anode to the cathode, so the anode is the negative terminal and the cathode is the positive terminal. To reduce the build up of charge, anions from the salt bridge flow to the anode, and cations flow to the cathode.

In an electrolytic cell, the anode is the positive terminal and the cathode is the negative terminal. Electrons still flow from anode to cathode, but they're being forced to do so (non-spontaneous) by a battery. Salt bridge is the same.

So which one is discharging, the galvanic cell??