Electrochemistry 1 Balancing Redox Reactions

Simple redox reactions can be balanced by the trial-and-error method described in Section 3.1, but other reactions are so complex that a more systematic approach is needed. There are two such systematic approaches often used for balancing redox reactions the oxidation-number method and the half-reaction method. Different people prefer different methods, so we ll discuss both. The oxidation-number method is useful because it makes you focus on the chemical changes involved the halfreaction method (discussed in the next section) is useful because it makes you focus on the transfer of electrons, a subject of particular interest when discussing batteries and other aspects of electrochemistry (Chapter 18). 

The half-reaction method for balancing redox reactions divides the overall redox reaction into oxidation and reduction half-reactions. Each half-reaction is balanced for atoms and charge. Then, one or both are multiplied by some integer to make electrons gained equal electrons lost, and the half-reactions are recombined to give the balanced redox equation. The half-reaction method is commonly used for studying electrochemistry because... 

The half-reaction method for balancing redox reactions is commonly used for studying electrochemistry for several reasons ... 

You had a brief introduction to the topic of electrochemistry in Chapter 11 when you reviewed the oxidation-reduction process in which reactions occur by the transfer of electrons. One of the procedures you looked at was the half-reaction method of balancing redox equations. In this chapter, we will be looking at the oxidation and reduction process in even more depth. 

Electrochemistry occurs through redox reactions, and its description requires balanced equations for redox reactions. Both topics are discussed in Section 11.4, which you should review now. 

This equivalence provides the basis for balancing redox equations. Although there is no single best method for balancing all redox equations, two methods are particularly useful (1) the half-reaction method, which is used extensively in electrochemistry (Chapter 21)... 

On commencing study of this topic, students should be comfortable with writing and balancing equations for chemical reactions (covered in greater depth in section 3.2 of Chapter 3). Knowledge of ions is also central. Concepts of basic electricity, such as electric current and potential difierence (a concept many students struggle with), are essential. Redox reactions (covered in Chapter 7) enter the study of electrochemistry... 

In this chapter, 1 explain redox reactions, go through the balancing of this type of equation, and then show you some applications of redox reactions in an area of chemistry called electrochemistry. 

Combustion is a redox reaction. So are respiration, photosynthesis, and many other biochemiccd processes people depend on for life. In this chapter, I explain redox reactions, go through the balancing of this type of equation, cind then show you some applications of redox reactions in an area of chemistry Ccdled electrochemistry. Electrochemistry is an cirea of chemistry in which we use chemical reactions to produce electrons (electricity) or use electrons (electricity) to cause a desired chemical reaction to take place. 

You will learn more about the importance of half-reactions when you study electrochemistry in Chapter 21. For now, however, you can learn to use halfreactions to balance a redox equation. First, look at an unbalanced equation taken from Table 20-3 to see how to separate a redox equation into half-reactions. For example, the following unbalanced equation represents the reaction that occurs when you put an iron nail into a solution of copper(II) sulfate, as shown in Figure 20-8. Iron atoms are oxidized as they lose electrons to the copper(ll) ions. 

You have learned two methods by which redox equations can be balanced. Both methods will provide the same results however, the half-reaction method may be more useful to your study of electrochemistry. 

---