Diagramming Voltaic Cells
Problem: Diagram, show balanced equations, and write the notation for
a voltaic cell that consists of one half-cell with a Cr bar in a Cr(NO3)3
solution, another half-cell with an Ag bar in an AgNO3 solution, and a
KNO3 salt bridge. Measurements show that the Cr electrode is negative
relative to the Ag electrode.
Plan: From the given contents of the half-cells, we write the half-
reactions. We must determine which is the anode compartment
(oxidation) and which is the cathode (reduction). To do so, we must find
the direction of the spontaneous redox reaction, which is given by the
relative electrode charges. Since electrons are released into the anode
during oxidation, it has a negative charge. We are told that Cr is negative,
so it must be the anode and, therefore, Ag is the cathode.
Solution: Writing the balanced half-reactions. Since the Ag electrode is
positive, the half-reaction consumes electrons:
Ag+(aq) + e- Ag(s) [reduction; cathode]
| Previous slide | Next slide | Back to first slide | View graphic version |