Electrochemistry I Batteries and Free Energy

Many of the simplest chemical reactions involve only an interchange of atoms or ions between reactants, or perhaps only the dissociation of one reactant into two parts. In such reactions, there is no change in the electrical charge of any of the atoms involved. This chapter deals with another type of reaction, in which one or more electrons are transferred between atoms, with the result that some of the atoms involved do have their electrical charges changed. These reactions are known as electron-transfer reactions. You can appreciate their importance when you realize that every battery used in electronic devices and machines, every impulse involved in nerve transmission, every metabolic reaction that produces energy in biological systems, photosynthesis, and combustion processes (to mention but a few examples) requires electron-transfer reactions. 

The process of donating and accepting electrons is reversible. For example, 

Reducing agents differ in their ability to donate electrons. Fpr example, meftlt lie Zn can donate electrons to Cd2+ to Produce mclallic Cd and7n2-,,  

A reversible electron-transfer reaction written in the form 

Note that all the components of one half-reaction are placed in one beaker, and all the components of the second half-reaction are placed in the other beaker. One must not put the materials of the lefthand side of the equation in one beaker, and those of the righthand side in the other If one did, electron transfer could occur on contact of the two reactants, and there would be no flow of current from one electrode to the other. The negative electrode always involves the half-reaction with the greatest reducing strength in this case it is a strip of zinc dipping into a solution of Zn2+ so ez nc sa 7- ThePOA7, ve 

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