Balancing equations oxidation number method

Of course, the oxidation number method gives the same balanced equation as the half-reaction method. 

In fact, you can use oxidation numbers to balance a chemical equation by a new method. The oxidation number method is a method of balancing redox equations by ensuring that the total increase in the oxidation numbers of the oxidized element(s) equals the total decrease in the oxidation numbers of the reduced element(s). 

In this section, you will write balanced equations for redox reactions using the oxidation number method... 

Use the oxidation number method to balance the following equation for the combustion of carbon disulfide. 

Q O The combustion of ammonia in oxygen to form nitrogen dioxide and water vapour involves covalent molecules in the gas phase. The oxidation number method for balancing the equation was shown in an example in this section. Devise a half-reaction method for balancing the equation. Describe the assumptions you made in order to balance the equation. Also, describe why these assumptions did not affect the final result. 

Gompare the half-reaction and oxidation number methods of balancing equations. 

The following redox reactions occur in basic solution. Balance the equations using the oxidation number method. 

The key to the oxidation-number method of balancing redox equations is to realize that the net change in the total of all oxidation numbers must be zero. That is, any increase in oxidation number for the oxidized atoms must be matched by a corresponding decrease in oxidation number for the reduced atoms. Take the reaction of potassium permanganate (KMn04) with sodium bromide in aqueous acid, for example. An aqueous acidic solution of the purple permanganate anion (Mn04 ) is reduced by Br- to yield the nearly colorless Mn2+ ion, while Br- is oxidized to Br2. The unbalanced net ionic equation for the process is... 

FIGURE 4.3 The proce- dure for balancing redox equations by the oxidation-number method. 

Worked Example 4.10 shows how the oxidation-number method is used to balance a reaction carried out in basic solution. The procedure is exactly the same as that used for balancing a reaction in acidic solution, but OH- ions are added as the final step to neutralize any H+ ions that appear in the equation. This simply reflects the fact that basic solutions contain negligibly small amounts of H+ but large amounts of OH-. 

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... 

Cybulski and Moulijn [27] proposed an experimental method for simultaneous determination of kinetic parameters and mass transfer coefficients in washcoated square channels. The model parameters are estimated by nonlinear regression, where the objective function is calculated by numerical solution of balance equations. However, the method is applicable only if the structure of the mathematical model has been identified (e.g., based on literature data) and the model parameters to be estimated are not too numerous. Otherwise the estimates might have a limited physical meaning. The method was tested for the catalytic oxidation of CO. The estimate of effective diffusivity falls into the range that is typical for the washcoat material (y-alumina) and reacting species. The Sherwood number estimated was in between those theoretically predicted for square and circular ducts, and this clearly indicates the influence of rounding the comers on the external mass transfer. 

Balancing a Redox Equation by the Oxidation-Number Method... 

If you try to balance the equation given above, you will see that it appears impossible. Net ionic equations can still be balanced, though, by applying the oxidation-number method, as you will see in Example Problem 20-4. The problem-solving LAB below shows how the oxidation-number method can be used for a real-world application. 

The oxidation-number method is convenient for balancing most redox equations, but you will see in the next section that there are occasions when you must balance the net ionic charge on both sides of the equation in addition to balancing the atoms. 

Many simple redox equations may be balanced by inspection. The oxidation-number method can be used to balance more difficult reactions. 

Two methods are commonly used to balance redox equations the half-reaction method and the oxidation number method. 

Most redox equations can be balanced and (2) the change-in-oxidation-number method. Many redox equations can be balanced... 

Note that oxygen appears in only one reactant, HNO3, but in all three products. Nitrogen appears in HNO3 and in two of the products. Redox equations such as this one, in which the same element appears in several reactants and products, can be difficult to balance. As you have read, when an atom loses electrons, its oxidation number increases when an atom gains electrons, its oxidation number decreases. The number of electrons transferred from atoms must equal the number of electrons accepted by other atoms. Therefore, the total increase in oxidation numbers (oxidation) must equal the total decrease in oxidation numbers (reduction) of the atoms involved in the reaction. The balancing technique called the oxidation-number method is based on these principles, and is described in Table 19.4. 

The Oxidation-Number Method Balance the following redox equation. 

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