Oxidation-reduction equations half-equation method

Complete and balance the following oxidation-reduction equations using the method of half-reactions. Both reactions occur in acidic solution. 

Balance the oxidation-reduction equation H+NO + H2S - NO + S + H20. Half-Reaction Method... 

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. 

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. 

Steps X Balancing Oxidation-Reduction Equations Occurring in Basic Solution by 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). 

A half-recution is a chemical equation representing only the oxidation or only the reduction of an oxidation-reduction reaction. Redox equations, which must be balanced for both mass and charge, can be balanced using the haff-reaction method. 

Balance oxidation-reduction equations using the half-reaction method. 

In the ion-electron method of balancing redox equations, an equation for the oxidation half-reaction and one for the reduction half-reaction are written and balanced separately. Only when each of these is complete and balanced are the two combined into one complete equation for the reaction as a whole. It is worthwhile to balance the half-reactions separately since the two half-reactions can be carried out in separate vessels if they are suitably connected electrically. (See Chap. 14.) In general, net ionic equations are used in this process certainly some ions are required in each half-reaction. In the equations for the two half-reactions, electrons appear explicitly in the equation for the complete reaction—the combination of the two half-reactions—no electrons are included. 

A We write down the oxidation half-equation with the method of Chapter 5, and obtain the reduction half-equation from Table 21-1, along with the reduction half-cell potential. 

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. 

In this method, the reaction is broken down into two half-reactions, oxidation and reduction half-reactions. Each half-reaction is balanced separately, so that the same number of electrons appear in each half-equation. Then, the two halfreactions are summed up to get a balanced net equation. 

An alternative to the oxidation-number method for balancing redox reactions is the half-reaction method. The key to this method is to realize that the overall reaction can be broken into two parts, or half-reactions. One half-reaction describes the oxidation part of the process, and the other half-reaction describes the reduction part. Each half is balanced separately, and the two halves are then added to obtain the final equation. Let s look at the reaction of aqueous potassium dichromate (K2Cr2C>7) with aqueous NaCl to see how the method works. The reaction occurs in acidic solution according to the unbalanced net ionic equation... 

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. 

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. 

The general procedure is to balance the equations for the half-reactions separately and then to add them to obtain the overall balanced equation. The half-reaction method for balancing oxidation-reduction equations differs slightly depending on whether the reaction takes place in acidic or basic solution. 

Oxidation-reduction reactions can occur in basic as well as in acidic solutions. The half-reaction method for balancing equations is slightly different in such cases. 

In the half-reaction method we separate and completely balance equations describing oxidation and reduction half-reactions. Then we equalize the numbers of electrons gained and lost in each. Finally, we add the resulting half-reactions to give the overall balanced equation. The general procedure follows. 

For each of the following unbalanced equations, (i) write the half-reactions for oxidation and for reduction, and (ii) balance the overall equation in acidic solution using the half-reaction method. 

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 Equations for Oxidation-Reduction Reactions Occurring in Acidic Solution... 

Use the half-reaction method to balance the redox equations. Begin by writing the oxidation and reduction half-reactions. Leave the balanced equation in ionic form. 

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