# What balances charges that may build up as reduction and oxidation occur in a voltaic cell?

There's a disagreement between me and my high school chemistry teacher regarding the answer to this question. I'm not convinced by his argument and neither is he convinced by my argument.

The problem goes as following

What balances charges that may build up as reduction and oxidation occur in a voltaic cell?

a. the salt bridge.

b. the electrolyte solutions

c. one of the half-cells

d. the moving electrons

We both agree that the word "charges" in the question refers to electrons. I argue that the answer is "a. the salt bridge". The salt bridge allows ions to pass to between the half-cells which prevents the build-up of charge on one of the half-cells due to the electrons, allowing the reaction to continue. So the salt bridge counter-acts or balances the charges. My teacher claims that the answer is "d. the moving electrons". He argues that moving the electrons balances the charges (I can't really phrase his argument).

My understanding of "balances the charges" is "counter-acts the effect of the charges". Perhaps this is where I just don't understand the question or my teacher. How can the movement of the electrons balance the charges or, in my understanding, counter-act the effect of the charges when it, in my understanding, is what creates the effect of the charges.

What is the correct answer and why?

• A bridge is optional, need not to be present if half cells share the electrolyte. Electrons are not present in electrolytes but ions. Free electrons reduce water in less then millisecond. Oct 20, 2022 at 6:07
• Also, electrons, coming and leaving, disbalance charges. Oct 20, 2022 at 6:32
• What a terribly asked exercise! You're both kind of correct and kind of wrong at the same time. The electrons from the oxidation half cell just move to the reduction half cell, answer d. At the same time, ions must travel the other way. This could be via a salt bridge, but that doesn't make it the correct answer. Oct 20, 2022 at 6:33