# Why can't a galvanic cell be a single cell?

I get that galvanic cells require a salt bridge to maintain neutrality so the cathode doesn't become saturated with electrons, but why is a two-cell setup required? Wouldn't the spontaneous reaction occur and neutral conditions be met if Cu and Zn electrodes were placed in a solution of NaCl?

And vice versa, couldn't an electrolytic cell work just fine with a salt bridge?

This website (and many others) leads me to believe that galvanic cells must have a salt bridge and electrolytic cells must be a single cell. My intuition says that's not right though. Is it because you don't want undesirable compounds reacting at the electrodes? I'd think you'd want the same for both EC cell types if that was the case and electrolytic cells would use salt bridges as well (eg proton exchange membranes). http://chem.libretexts.org/Core/Analytical_Chemistry/Electrochemistry/Electrolytic_Cells

• Sure, galvanic cell would work for a while in a single cell setup, but you'll get a lot of side reactions which you don't want. On the other hand, electrolytic cell would work just fine in a two-cell setup with a salt bridge, but then half of your solution would be effectively excluded from the reaction, which we didn't ask for. Also, welcome to Chem.SE. – Ivan Neretin Jan 12 '17 at 6:17
• Thanks. Wouldn't separating the cells in an electrolytic cell be more desirable than galvanic to reduce the back (spontaneous) reaction of by-products? For example, in electrolytic water splitting, the chamber are separated with a proton exchange membrane to reduce back reaction of hydrogen and oxygen to water. Why do introductory texts then claim electrolytic and galvanic cells must be 1 and 2 celled, respectively? Or are they just simplifying it? – prof.kvothe Jan 12 '17 at 15:35
• That's it: they are just simplifying. – Ivan Neretin Jan 12 '17 at 15:44

By comparison, the construction of a lithium ion cell is close to what you describe for a single chamber galvanic cell. There is a separator involved but mostly to keep the two electrodes from coming into direct contact. One reason this is possible is that the electrolyte is an organic solvent (usually ethylene carbonate, dimethyl carbonate, etc) and doesn't conduct electrons, even when the appropriate salt (eg. $\ce{LiPF6}$) is dissolved in it. There is no salt bridge in this cell, though it is clearly galvanic.