Question

In pretty much all introductory chemistry courses, the galvanic cell (i.e., battery) is introduced as a system of two half-cells with a salt bridge converting chemical energy to electrical energy. From what I understand, this is what is called a Daniell cell. For example,Zn(s)|Zn₂+(aq)||Cu₂+(aq)|Cu(s)|Zn(s)|Zn(aq)₂+||Cu(aq)₂+|Cu(s)|with an NaCl(aq)salt bridge. However, we can design a much simpler battery using only one cell:Zn(s)Zn(s)andCu(s)Cu(s)electrodes both dipped in the same H₂SO₄(aq)solution (similar to a lemon battery). Both designs would produce the same voltage (~1.10V). But since the latter design is simpler/more practical/cheaper/etc., why do most resources exclusively talk about the Daniell cell?

Answer 1

The Daniell cell's dual half-cell configuration is preferred in educational materials over the single half-cell design because it clearly demonstrates the electrochemical principles of a galvanic cell and allows controlled study of individual reactions and ion flow.

Step-by-step explanation:

Differences Between Single Half-Cell and Daniell Cell

When comparing two designs for a galvanic cell, such as the simpler single half-cell design where both zinc and copper electrodes share the same acidic solution versus the Daniell cell, there are fundamental reasons for the popularity of the latter in educational materials. The Daniell cell consists of two separate half-cells connected by a salt bridge and is able to provide a clear illustration of electrochemical principles, including the flow of electrons and ions between cells, and the maintenance of electrical neutrality. This setup allows for detailed study of the individual reactions at each electrode.

In contrast, the single half-cell design, although simpler and potentially cheaper, combines both reactions in a single solution. This can lead to complications like the mixing of half-reactions, which could potentially result in a less stable voltage output compared to the separated half-cells in the Daniell cell. Moreover, the Daniell cell's configuration facilitates the study of redox reactions in a controlled manner, highlighting important concepts such as anode/cathode functions and the direction of ion flow through the salt bridge.

Additionally, the usage of solid or concentrated reactants in commercial batteries is designed to maximize electrical output and maintain stable voltage during discharge, principles best demonstrated by the dual half-cell setups like the Daniell cell.