[geo.mcc]

in a galvanic cell, why is the salt bridge neccisary?
i understand that it is to prevent the accumulation of charge, but why does an accumulation of charge prevent the reaction going ahead, surely the electrodes keep pulling the electrons through the wire?
if there is no salt bridge present, does the reaction only occur for a tiny amount of time, or does it not occur at all?

Thanks for any help.

[Donaldson Tan]

http://www.chemicalforums.com/index.php?topic=7550.0

http://www.chemicalforums.com/index.php?topic=6537.0

How can electron transfer occur without a salt bridge?

[geo.mcc]

but isnt the wire transferring electrons and the salt bridge transferring ions?
Why does a build up of charge prevent current from continuing to flow?

[Donaldson Tan]

in a galvanic cell, why is the salt bridge neccisary?

It is not necessary. You can have both electrodes connected in the same container of electrolyte. The reason of using salt bridge is to minimise interaction between ionic species which may reduce the electrical output of the galvanic cell.

maybe this picture answers your question?

Using the example above, you would observe that Zn²⁺ ions would be released into the electrolyte. It cannot interact with Cu²⁺ because it is absent in the electrolyte in which the zinc cations are released into.

What do you think are the interactions between Cu²⁺ and Zn²⁺?

How does presence of Cu²⁺ affect the release of Cu²⁺ from the Zn electrode?

Is there competition among the cations to be discharged?

[Borek]

Why does a build up of charge prevent current from continuing to flow?

Think in terms of potential and counterpotential.