In dry cell free electrons are released at anode or cathode
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The charge of the anode and the cathode depends on whether it is a Galvanic cell (spontaneous chemistry driving electricity) or an electrolysis cell (non-spontaneous chemistry driven by forcing electricity from an external energy source. The negative charge that develops will depend on where the electrons run into resistance and have difficulty passing. So you cannot use the charge on the electrode as an indicator of current direction.
The anode is always where oxidation happens and the cathode is always where reduction happens.
Oxidation is where an element gives up one or more electrons to become more positively charge (higher oxidation state). In either type of cell, those electrons leave the chemicals and head out onto the external circuit.
Reduction is where an element picks up an electron to become more negatively charge (less positive, lower oxidation state). In either type of cell, those electrons are picked up off the external circuit.
So, no matter what type of cell you are working with, the electrons are put onto the external circuit at the anode by the chemicals that are oxidized, where they then travel through said circuit from the anode to the cathode, where they are picked up by the chemical that is being reduced. The electrons ALWAYS travel through the external circuit from the anode to the cathode (alphabetic direction a → c).
A common confusion point is the charge on the electrodes. The sign of the charge depends on where the source and resistance are located.
For the Galvanic cell, the source is the spontaneous chemical reaction and the resistance is in the external circuit. So the anode will be negative as that is where the electrons will pile up while trying to force their way through the resistance on the external circuit. The anode is negative.
For an electrolysis cell, the source is an external battery on the circuit. It’s the chemicals that don’t want to react that create the resistance. So the electrons pile up on the cathode until they can force their way onto the chemicals to force the reaction. The cathode is negative.
The anode is always where oxidation happens and the cathode is always where reduction happens.
Oxidation is where an element gives up one or more electrons to become more positively charge (higher oxidation state). In either type of cell, those electrons leave the chemicals and head out onto the external circuit.
Reduction is where an element picks up an electron to become more negatively charge (less positive, lower oxidation state). In either type of cell, those electrons are picked up off the external circuit.
So, no matter what type of cell you are working with, the electrons are put onto the external circuit at the anode by the chemicals that are oxidized, where they then travel through said circuit from the anode to the cathode, where they are picked up by the chemical that is being reduced. The electrons ALWAYS travel through the external circuit from the anode to the cathode (alphabetic direction a → c).
A common confusion point is the charge on the electrodes. The sign of the charge depends on where the source and resistance are located.
For the Galvanic cell, the source is the spontaneous chemical reaction and the resistance is in the external circuit. So the anode will be negative as that is where the electrons will pile up while trying to force their way through the resistance on the external circuit. The anode is negative.
For an electrolysis cell, the source is an external battery on the circuit. It’s the chemicals that don’t want to react that create the resistance. So the electrons pile up on the cathode until they can force their way onto the chemicals to force the reaction. The cathode is negative.
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