Galavanic cell salt bridge conecpt...

[MegaSpectacular]

I am going over galvanic cells right now. I understand the whole logic of oxidation and reduction of each half cell, for example:

but the salt bridge is throwing me off. Say we have a salt bridge of KNO3-. The explanation of the salt bridge wasn't good enough in my prep books, so I searched online. I was able to take notes and determine the purpose of the salt bridge is:

• salt bridge made of KNO3
• anions from the salt bridge go to the anode
• cations from the salt bridge go to the cathode

salt bridge:

• flow of electrons causes charge delta
• no salt bridge? charge difference would stop flow
• salt bridge allows there to be a charge balance; balanced charge means electrons can flow again

My question is, how does the charge difference stop the flow of electrons (i.e. if there was no salt bridge)? thinking of equilibrium, I would think a charge difference would cause electron flow and a balanced charge would eliminate the flow of electrons.

According to wikipedia, salt bridge allows there to be a charge balance, which then allows electrons to flow. Why am I thinking that equilibrium or balanced charge would result in no flow of electrons?

Confused a bit here. Any help is much appreciated.

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[loveoforganic]

Is it favorable to keep pushing negative charge into negative charge? The electrical gradient would rapidly cancel out the chemical voltage of the cell by opposing it. The movement of spectator ions allows the electrical gradient to be rapidly dissipated, allowing the reaction to run to completion.

 

[unique135]

Agree with loveoforganic,

Salt bridge increases the cell life.

[YOUTUBE]http://www.youtube.com/watch?v=A0VUsoeT9aM[/YOUTUBE]

 

[SirWilliamOsler]

I know that a galvanic cell has a (-) delta G and a (+) emf.

Does the electrolytic cell have a (+) delta G and a (-) emf?

 

[loveoforganic]

Only when you don't factor in the applied voltage to get the reaction to run in that direction.

 

[SirWilliamOsler]

I found this great link on how to calculate the cell's emf. Hope it helps!

http://www.ausetute.com.au/calcelemf.html

 

[Snowbeavers]

At the anode, a rapidly positive charge is building up due to the Zn++ ions, the negative ions must balance out the charge from the salt bridge.

I suppose if there was too much of a positive charge, electrons would be attracted to the positive charge at the anode which would reduce to flow into the cathode.