38 Fuel Cells
The reactions at each half-cell are given as
Zn(s) → Zn
2+
(aq) + 2e
−
(2.1)
Cu
2+
(aq) + 2e
−
→ Cu(s) (2.2)
Here, the symbols in the parentheses refer to the material state: s, solid;
aq, aqueous solution. In one half-cell with zinc sulfate, the Zn loses two elec-
trons (oxidizes), and in the other cell, Cu
2+
accepts two electrons (reduces).
The Zn electrode loses Zn as Zn
2+
ion into the solution and appears as cor-
roded. The Cu electrode is being plated with Cu from the electrolyte. As
the cell operates, ions move through the partition or salt bridge to keep the
individual cells electrically neutral. Because of the charge accumulation at
one electrode, the driving force is created and the electrons travel through
the wire generati ...