Question

What kind of salt bridge do you normally find in a galvanic cell with Ag and Zn electrodes? Also, what solution would you put the electrodes in?

Ex: for Cu and Zn, you would put them in solutions of Cu(NO3)2 and Zn(NO3)2, respectively, and put KNO3 in the salt bridge. So what about for Ag and Zn?

Answer 1

For Ag and Zn, the only change is to use `AgNO_3` in place of `Cu(NO_3)_2`

Explanation:

In first explaining the operation of an electrochemical cell, it is common to consider half-cells in which each metal is immersed in a solution made from a soluble salt of that same metal.

So, if the electrodes are Zn and Ag, the electrolytes should be `Zn(NO_3)_2` and `AgNO_3`, because silver nitrate is the only soluble salt of silver.

This is done because we wish to make it possible for either the metal electrode to oxidize (if it happens to be the anode in the cell) or for the ions in the solution to reduce, if it should be the cathode half-cell. This is only for the sake of ensuring that both metals and both ions are present, and requiring that the student make a decision in regards to which chemicals actually react.

In fact, only one of the salts will actually undergo a change.

As to the salt bridge, it is best to use a salt that will not result in an unwanted reduction that might alter the operation of the salt (and particularly, the cathode). Potassium nitrate is a common choice, as potassium ions have very low tendency to reduce.