A simple electrochemical cell

The schematic below illustrates a simple electrochemical cell.


In short an electrochemical cell functions as a battery. Recall that a current is simply a flow of electrons. In an electrochemical cell, the electron transfer that occurs during a redox reaction is made to flow through an external circuit.

How do we identify which species is donating the electron and which species is accepting the electrons? We can make use of the standard electrode values in the data booklet.
From the electrode values we can see that Cu2+ is more likely to be reduced compared to Zn2+. Hence we make Cu2+ the species that is to be reduced and Zn(s) would be the species that will be oxidized, i.e. the electron donating species. If you calculate the standard cell potential, we will see that the standard cell potential is positive, indicating that the reaction is feasible.

Students should note that for an electrochemical cell, the standard cell potential is always positive.