Question

What assures that there is no charge build up in a voltaic cell as oxidation and reduction occur?

one of the half cells
the electrolyte solutions***
the moving electrons
the salt bridge

Answer 1

im pretty sure the answer is salt bridge

Answer 2

im gonna have to agree with anonymous

Answer 3

I would go with salt bridge, also.

Answer 4

That is correct (100%)... The anion from the salt bridge migrates to the anodic cell to off set the build up of cations from oxidation and the cation from the salt bridge migrates to the cathodic cell to offset the loss of cations being reduced to basic standard state.

Just to add an FYI, this is why when designing a battery, the cation concentration in the anodic cell is minimized and the cation concentration in the cathodic cell is maximized. As the Galvanic process discharges the cation concentration in the anodic cell increases b/c of oxidation requiring migration of anion from the salt bridge and the concentration of cation in the cathodic cell decreases requiring migration of the salt bridge cation to the cathode cell. The anodic electrode continues to undergo oxidation until completely dissolved, or the total concentration of cation in the cathodic cell is completely reduced giving a really dead battery.