Simple question (electrochemistry)

[jasoN-]

The purpose of the salt bridge is to inhibit polarization/the build up of charges, and keeping the two solutions separated.
My question is what happens when there is a build up of charges?
Why does it stop the electron flow and thus the current flow? (Also is it instantaneous? If the salt bridge is removed will it(the current+electron flow) instantly stop?)

In an exam do we need to know the answer to these questions? Or simply "the salt bridge inhibits polarization/the build up of charges"

Thanks

(even if we dont need to know im curious as to why the current stops)

[masonnnn]

if there's a build up of charges that means there's no electrical circuit/flow of charges, so all the energy will just be given off as thermal energy... thus just a waste of time.
and electricity only flows if it has a complete circuit so without the salt bridge there is no circuit so yes, the electron flow/ current will stop.
seeing how fast electricity flows i'd assume it'd be a pretty instantaneous stopping of the current, not positive though... physics people would be more useful for this.

[Blakhitman]

If there was no salt bridge, the anode will increase positivity until the electrons wouldn't wanna move to the cathode anymore, hence no current.

[jasoN-]

Ah ok thanks guys.
I did the experiment today, it seems that if the circuit is broken (ie. removal of the salt bridge) it is instant.

How does electricity travel through the salt bridge? Is it chemically?

[Mao]

if there's a build up of charges that means there's no electrical circuit/flow of charges, so all the energy will just be given off as thermal energy... thus just a waste of time.
and electricity only flows if it has a complete circuit so without the salt bridge there is no circuit so yes, the electron flow/ current will stop.
seeing how fast electricity flows i'd assume it'd be a pretty instantaneous stopping of the current, not positive though... physics people would be more useful for this.

Spot on, a very small amount of current will occur, but this only lasts a tiny amount of time, since electrons flow fairly fast, and electric charges exert very strong repulsion to each other (the charge displacement of the electrodes will be tiny).

After that though, there will be no reaction. No energy will be dissipated via heat (if done right), since the two species cannot react because charge is saturated at both cells. It'll simply stop [or rather, reach equilibrium, where the rate of forward reaction (favoured by electrochemistry) slows to a virtual stop at the same value as the rate of backward reaction (very, very, very, very slow reaction)].

Electricity does not travel through the salt bridge. The salt bridge simply supply the correct counter-ions (such as K+ and NO3-) to balance the flow of electrons in the two cells.

[jasoN-]

Awesome, thanks Mao.
So if the salt bridge was removed, the ions will all be used up (almost instantaneously) and hence the cell has reached equilibrium and the current/electron flow ceases.