Balancing Oxidation-Reduction Reactions by the Half-Reaction Method

Is this an oxidation-reduction reaction If so, specify the oxidizing agent and the reducing agent. 

Balancing Oxidation-Reduction Reactions by the Half-Reaction 17.4) Method 

I AIM To learn to balance oxidation-reduction equations by using half-reactions. 

Many oxidation-reduction reactions can be balanced readily by trial and error. That is, we use the procedure described in Chapter 6 to find a set of coefficients that give the same number of each type of atom on both sides of the equation. 

However, the oxidation-reduction reactions that occur in aqueous solution are often so complicated that it becomes very tedious to balance them by trial and error. In this section we will develop a systematic approach for balancing the equations for these reactions. 

To balance the equations for oxidation-reduction reactions that occur in aqueous solution, we separate the reaction into two half-reactions. Half-reactions are equations that have electrons as reactants or products. One half-reaction represents a reduction process and the other half-reaction represents an oxidation process. 

In a reduction half-reaction, electrons are shown on the reactant side (electrons are gained by a reactant in the equation). In an oxidation halfreaction, the electrons are shown on the product side (electrons are lost by a reactant in the equation). 

To balance the equations for oxidation-reduction reactions that occur in aqueous solution, we separate the reaction into two half-reactions. Halfreactions are equations that have electrons as reactants or products. One half-reaction represents a reduction process and the other half-reaction represents an oxidation process. In a reduction half-reaction, electrons are shown on the reactant side (electrons are gained by a reactant in the equation). In an oxidation half-reaction, the electrons are shown on the product side (electrons are lost by a reactant in the equation). 

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Balancing Oxidation-Reduction Reactions by the Half-Reaction Method 1 7.5 Electrochemistry An Introduction 1 7.6 Batteries 1 7.7 Corrosion 1 7.8 Electrolysis... 

In lesson C the student must know the definition of molarity and moles, the quantitative relationship of a chemical equation to determine quantities of reactants and products for reactions. Lesson D has the following objectives Assignment of oxidation numbers to elements according to a set of rules balancing oxidation-reduction equations by the half-reaction method and identification of oxidizing and reducing agents. 

The half-reaction method is a way of balancing oxidation-reductions reactions by the recognition of oxidation and reduction with separate reactions. Included in the reactions are the number of electrons that move and the nature of movement (gain or loss). The steps for this technique are ... 

The following steps may be used to balance oxidation—reduction (redox) equations by the ion-electron (half-reaction) method. While other methods may be successful, none is as consistently successful as is this particular method. The half-reactions used in this process will also be necessary when considering other electrochemical phenomena, thus the usefulness of half-reactions goes beyond balancing redox equations. 

In section 10.2, you learned that a redox reaction involves changes in oxidation numbers. If an element undergoes oxidation, its oxidation number increases. If an element undergoes reduction, its oxidation number decreases. When balancing equations by the half-reaction method in section 10.3, you sometimes used oxidation numbers to determine the reactant(s) and product(s) in each half-reaction. 

The first step in any method of balancing oxidation-reduction equations is to identify the element that is oxidized and the one that is reduced. Because the change in oxidation number is equal to a change in the number of electrons controlled, and the electrons must be controlled by some atom, the total gain in oxidation number is equal to the total loss in oxidation number. The oxidation half of a reaction may be written in one equation, and the reduction half in another. Neither half-reaction can be carried out without the other, but they can be done in different locations if they are connected in such a way that a complete electrical circuit is made (Chapter 17). The half-reaction method is illustrated by balancing the equation for the reaction of zinc metal with dilute nitric acid to produce ammonium ion, zinc ion, and water ... 

Oxidation is defined as a gain in oxidation number, caused by a loss of electrons or of control of electrons. Reduction is defined as a loss in oxidation number, caused by a gain of electrons or of control of electrons. Complicated oxidation-reduction equations must be balanced according to some systematic method because they are too complex to be balanced by inspection. Although neither can take place alone, the oxidation and the reduction can occur in different locations if suitable electrical connections are provided. (Chapter 17) In the halfreaction method, the equation for the half-reaction involving oxidation and that for the half-reaction involving reduction are balanced separately then the two are combined. Each may be multiplied by a small integer if necessary to balance the numbers of electrons involved. 

Oxidation-reduction reactions are often complicated, which means that it can be difficult to balance their equations by simple inspection. Two methods for balancing redox reactions will be considered here (1) the oxidation states method and (2) the half-reaction method. 

Balancing Oxidation-Reduction Equations Occurring in Acidic Solution by the Half-Reaction Method... 

Each of the oxidation-reduction reactions place in acidic solution. Balance each reaction by using the half-reaction method. 

Oxidation-reduction equations can be balanced by inspection or by the half-reaction method. This method involves splitting a reaction into two parts (the oxidation half-reaction and the reduction halfreaction). 

Balance each of the following oxidation-reduction reactions, which take place in acidic solution, by using the "half-reaction" method. 

To complete and balance Equation 20.6 by the method of half-reactions, we begin with the unbalanced reaction and write two incomplete half-reactions, one involving the oxidant and the other involving the reductant. 

Balancing simple oxidation-reduction reactions by the half-reaction method Given an oxidation-reduction reaction, balance it. (EXAMPLE 4.8)... 

Balance the following oxidation-reduction reactions by the half-reaction method. 

An oxidation-reduction reaction can also take place in basic solution. In that case, we use the same half-reaction method, but once we have the balanced equation, we will neutralize the with OH to form water. The is neutralized by adding OH to both sides of the equation to form H2O as shown in Sample Problem 15.5. 

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