Salt Bridge Purpose in Galvanic Cells

Elisa_Rojas Palato
Elisa_Rojas Palato Posts: 2

MCAT Student

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in Pre-Med Success Community

Hi! After searching and googling, I couldn't find a good answer for why the salt bridge is important in the Galvanic Cells. From what I have found, all answers mention salt bridge prevent the unbalanced charge difference caused by electrons (e) moving from the anode to the cathode where they interact with the ion that has a higher reduction potential. However, I don't understand how this charge difference forms in the first place. Wouldn't it be the case that as e-s move from the anode to the cathode, they reduce the cation (e.g., Cu2+ + 2e-s → Cu (s) ) such that there aren't flowing e's in the solution because they have all been hypothetically used to reduce the cation? So I don't see how the charge difference develops and becomes a problem. And how the common anion (e.g. sulfate) can alleviate it. Does the anion induce the oxidation of the metals on the anode? Please feel free to provide an example (e.g. Cu2+ and ZN2+) to illustrate this. Thank you in advance to anyone/people who answer this question!!!!!

source: Kaplan FL3, Chem/phys, Quetion 52

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  • Ae-Ri
    Ae-Ri Posts: 171

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    Hi Elisa!

    Happy to help. I've drawn it out in a diagram below. As the copper is reduced, it depletes the copper side of positive charge since Cu2+ is being used up, which is why cations ALWAYS flow to the cathode. As the nickel is oxidized, it introduces more positive charge from Ni2+ ions being formed, so anions from the salt bridge ALWAYS flow to the anode. Both ions in the salt bridge dissipate the electrostatic repulsion that would quickly build up in both cells that would stop the flow of electrons. The identity of the anions and cations from the salt bridge aren't important - they just need to not react in the electrochemical reactions. Does that answer your question?

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