Acidic solution balancing oxidation-reduction equations

Balancing oxidation-reduction equations for reactions occurring in aqueous acidic solutions is usually fairly straightforward since we can use H20 to balance O, and then H+ to balance H. In basic solution,... 

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. 

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

Although the preceding skeleton equation is not complete, it does give the essential information about the oxidation-reduction reaction. Moreover, given the skeleton equation, you can complete and balance the equation using the half-reaction method. Let us see how to do that. We first look at balancing oxidation-reduction equations in acidic solution. To balance such equations in basic solution requires additional steps. 

Steps in Balancing Oxidation-Reduction Equations in Acidic Solution... 

Write plausible half-equations and a balanced oxidation-reduction equation for the disproportionation of Xep4 to Xe and Xe03 in aqueous acidic solution. Xe and Xe03 are produced in a 2 1 mole ratio, and 02(g) is also produced. 

Balance the oxidation-reduction equation for the oxidation of H2S(aq) by HN03(aq) to produce NO(g) and S(s) in aqueous acidic solution (thus H+ and H20 may be involved). 

When this oxidation-reduction equation is balanced in acidic solution, using only whole number coefiTicients, what is the coefficient for S(s l... 

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

To balance an oxidation—reduction equation in basic solution, you begin by balancing the equation as if it were a reaction in acidic solution. Then, you add the following steps. ... 

Balancing equations in acidic and basic solutions by the half-reaction method Given the skeleton equation for an oxidation-reduction equation, complete and balance it. (EXAMPLES 20.1,20.2)... 

Balance the following oxidation-reduction equations. The reactions occur in acidic or basic aqueous solution, as indicated. 

Oxidation-reduction equations are now balanced using half-reactions in acidic or basic solutions. 

Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction. 

B Since we need to refer to Table 21-1 in any event, it is perhaps a bit easier to locate the two balanced half-equations in the table. There is only one half-equation involving both Fe2+(aq) and Fe3+(aq) ions. It is reversed and written as an oxidation below. The halfequation involving Mn04 (aq) is also written below. [Actually, we need to know that in acidic solution Mn2+(aq) is the principal reduction product of Mn04 (aq).]... 

Write partial equations for the oxidation and the reduction. Then (1) Balance charges by adding in acid solutions or OH in basic solutions. (2) Balance the number of O s by adding H O s to one side. (3) Balance the number of H s by adding H s to one side. The number added is the number of equivalents of oxidant or reductant. 

Write balanced ionic half-reaction equations for the reduction of each of the following oxidizing agents in acid solution. 

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... 

Most aqueous reaction equations can be balanced by trial and error. Oxidation-reduction reactions require a more systematic approach to balancing equations using either an 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. 

Equations for redox reactions are sometimes difficult to balance. Use the steps in Skills Toolkit 2 below to balance redox equations for reactions in acidic aqueous solution. An important step is to identify the key ions or molecules that contain atoms whose oxidation numbers change. These atoms are the starting points of the unbalanced half-reactions. For the reaction of zinc and hydrochloric acid, the unbalanced oxidation and reduction half-reactions would be as 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. 

It turns out that most oxidation-reduction reactions occur in solutions that are distinctly basic or distinctly acidic. We will cover only the acidic case in this text, because it is the most common. The detailed procedure for balancing the equations for oxidation-reduction reactions that occur in acidic solution is given below, and Example 18.5 illustrates the use of these steps. 

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