In the Zn/cu cell, once the reaction starts, excess ions begin to accumulate in both the half cells. To maintain the electrical neutrality, a salt bridge is used. how does the salt bridge actually work?

For example, if we use NaCl salt bridge, does ZnCl2 get precipitated in the anodic half cell?

  • $\begingroup$ It could, but ZnCl2 is very soluble in water. 432.0 g/ 100 g (25 °C) . $\endgroup$ – MaxW Oct 23 '18 at 13:18
  • $\begingroup$ Salt bridge works by letting the excess ions move someplace else, so in the end there is no excess. $\endgroup$ – Ivan Neretin Oct 23 '18 at 13:23

The function of the salt bridge is to supply appropriate ions to the solutions to maintain electrical balance.

At the cathode, as reduction occurs, positive ions are taken from solution and deposited on the Cu cathode. To replace this, positive ions from the salt bridge will preferentially move into that side of the cell.

At the anode, neutral elemental Zn is oxidizing into Zn+2 ions and negative ions from the salt bridge will move to this half of the cell to maintain charge neutrality.

Very nice diagram and description from U Texas website here

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