Basic solutions half-reaction method

The Sample Problem on the next page illustrates the use of these steps for an acidic solution. To balance a net ionic equation for basic conditions by the half-reaction method, balance each half-reaction for acidic conditions, adjust for basic conditions, and then combine the half-reactions to obtain the balanced net ionic equation. The following Concept Organizer summarizes how to use the half-reaction method in both acidic and basic conditions. 

The following redox reactions occur in basic solution. Use the half-reaction method to balance the equations. 

PROBLEM 4.20 Balance the following equation by the half-reaction method. The reaction takes place in basic solution. 

To balance a redox reaction which occurs in a basic solution is a very similar to balancing a redox reaction which occurs in acidic conditions. First, balance the reaction as you would for an acidic solution and then adjust for the basic solution. Here is an example using 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. 

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

Balance the following oxidation-reduction reactions, which occur in basic solution, using the half-reaction method. 

Use the half-reaction method to balance these equations. Add water molecules and hydrogen ions (in acid solutions) or hydroxide ions (in basic solutions) as needed. Keep balanced equations in net ionic form. 

The Half-Reaction Method for Balancing Equations for Oxidation-Reduction Reactions Occurring in Basic Solution... 

In using the half-reaction method, we usually begin with a skeleton ionic equation showing only the substances undergoing oxidation and reduction. In such cases, we usually do not need to assign oxidation numbers unless we are unsure whether the reaction involves oxidation-reduction. We will find that H (for acidic solutions), OH (for basic solutions), and H2O are often involved as reaaants or products in redox reactions. Unless, ... 

When balancing redox reactions occurring in basic solutions, the text instructs you to first use the half-reaction method as specified for acidic solutions. What if you started by adding OH first instead of H+ What potential problem could there be with this approach ... 

In Chapter 4 (Section 4.6) we introduced the half-reaction method of balancing simple oxidation-reduction reactions. We now extend this method to reactions that occur in acidic or basic solution. The steps used to balance these equations successfully are built upon those presented in Chapter 4. Keep in mind that oxidation-reduction reactions involve a transfer of electrons from one species to another. For example, in the reaction described in the chapter opener, zinc metal becomes zincfll) ion each zinc atom loses two electrons, and copper(II) ion becomes copper metal (each copper ion gains two electrons). 

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. 

Oxidation—reduction reactions involve a transfer of electrons from one species to another. The half-reaction method can be applied to balancing oxidation-reduction reactions in acidic and basic solutions. Many of the principles required for balancing these reactions were presented in Chapter 4. 

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)... 

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. 

To balance redox reactions occurring in basic solution, follow the half-reaction method outlined in Examples 18.1 and 18.2, but add an extra step to neutralize the acid with OH as shown in step 3. 

We can balance redox reactions using the half-reaction method, in which the oxidation and reduction reactions are balanced separately and then added. This method differs slightly for redox reactions in acidic and in basic solutions. 

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