4
$\begingroup$

I was reading about electrochemical cells and I really don't understand why a salt bridge is needed. Can't you just combine the solutions? I've found a lot of webpages explaining electrochemical cells but strangely enough none of them seem to find this important enough to explain. All thoughts appreciated :)

$\endgroup$
  • $\begingroup$ Can you give an example of cell's material ? (electrolyte and electrode) $\endgroup$ – Babounet Mar 22 '15 at 13:08
  • $\begingroup$ I'm going by this: chem1.com/acad/webtext/elchem/ec2.html so a Zn and Cu electrode, and Zn[sup]2+[/sup] and Cu<sup>2+</sup> ions (and NO<sub>3</sub><sup>-</sup>) $\endgroup$ – Plumpie Mar 22 '15 at 13:17
  • 1
    $\begingroup$ What do you think would happen if you put a zinc plate into a copper ion solution? $\endgroup$ – Nicolau Saker Neto Mar 22 '15 at 13:22
  • 1
    $\begingroup$ I think I understand, the copper ions would combine with electrons from the Zn because copper apparently attracts electrons much harder, and then Zn would dissolve to give Zn2+. So you can't bring the solutions together because then your electrode would dissolve. $\endgroup$ – Plumpie Mar 22 '15 at 13:26
  • 1
    $\begingroup$ Correct. The zinc electrode would partially dissolve, and most of the copper ions in solution would deposit on it as a copper metal plating. Since the battery needs copper ions to work, by causing most of them to deposit directly on the zinc electrode, you're basically discharging the cell without collecting any electrons through the external circuit. $\endgroup$ – Nicolau Saker Neto Mar 22 '15 at 16:07
2
$\begingroup$

The use of a salt bridge is to maintain the electrical neutrality throughout the cell.

A salt bridge will allow the movement of ions. Electrons flow from anode to cathode.Due to this a negative charge will be developed in the cathode and a positive charge in the anode.This charge developed will oppose the electron flow (current from anode to cathode) and at one level the electron flow will be ceased.So the cell's action will be stopped. So in order to prevent this, salt bridges are used.

There is a similar question in this site.Please refer that.

Why is it important to use a salt bridge in a voltaic cell? Can a wire be used?

$\endgroup$
1
$\begingroup$

There are a lot of cases where you can work without a salt bridge. If the two reactions(reduction and oxidation) don't interfere with each other, you can just let the solution be in a single pot.

It is only there to separate the two solutions and still maintain ionic contact.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.