Oxidation-reduction reactions balanced redox reaction

From Appendix 3, it will be seen that the value of for the copper couple is more positive than that of the iron couple, so it is the copper couple which undergoes reduction. Accordingly, the iron couple undergoes oxidation, and the balanced redox reaction is Cu " " + 2Fe + -> Cu° + 2Fe. ... 

Balancing numerous chemical reactions often involves exchanges of electrons between different species. These reactions are called oxidation-reduction reactions, oxido-reduction reactions, or redox reactions. They can take place in a homogeneous phase, specifically within a solution. They can also take place in a heterogeneous medium, on the surface of electrodes. In the first case, we simply speak of redox reactions (it is understood in solution). In the second, we speak of electrochemical reactions. 

We conventionally cite the oxidized form first within each symbol, which is why the general form is o,r> so pb4+ Pb + is correct, but 2+ 4+ is not. Some people experience difficulty in deciding which redox state is oxidized and which is the reduced. A simple way to differentiate between them is to write the balanced redox reaction as a reduction. For example, consider the oxidation reaction in Equation (7.1). On rewriting this as a reduction, i.e. Al3+(aq) + 3e = A Em, the oxidized redox form will automatically precede the reduced form as we read the equation from left to right, i.e. are written in the correct order. For example, o,r for the couple in Equation (7.1) is Ai3+,ai-... 

The usefulness of determining the oxidation number in analytical chemistry is twofold. First, it will help determine if there was a change in oxidation number of a given element in a reaction. This always signals the occurrence of an oxidation-reduction reaction. Thus, it helps tell us whether a reaction is a redox reaction or some other reaction. Second, it will lead to the determination of the number of electrons involved, which will aid in balancing the equation. These latter points will be discussed in later sections. 

In this chapter, you will be introduced to oxidation-reduction reactions, also called redox reactions. You will discover how to identify this type of reaction. You will also find out how to balance equations for a redox reaction. 

First, balance the number of atoms then, balance all of the transferred electrons. However, these simple rules are often difficult to apply in oxidation-reduction reactions (redox reactions). 

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. 

Balancing oxidation-reduction reactions depends on whether the solution is acidic or basic. The method for balancing redox reactions in an acidic solution is as follows ... 

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. 

In oxidation-reduction reactions, electron transfers (e ) are coupled with the transfer of protons (H ) to maintain a charge balance. A modification of the redox balance corresponds to a modification of the acid-base balance. The net reactions of the oxidation of C, S, and N exceed reduction reactions in these elemental cycles. A net production of ions in atmospheric precipitation is a necessary consequence. The disturbance is transferred to the terrestrial and aquatic environments, and it can impair terrestrial and aquatic ecosystems. 

Describe how an oxidation-reduction reaction may be broken down into two half-reactions, and explain why the latter are useful in balancing redox equations. 

You already know that chemical equations are written to represent chemical reactions hy showing what substances react and what products are formed. You also know that chemical equations must be balanced to show the correct quantities of reactants and products. Equations for oxidation-reduction reactions are no different. In this section, you ll learn a specific method to balance redox equations. 

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... 

We know that in an oxidation-reduction reaction we must ultimately have equal numbers of electrons gained and lost, and we can use this principle to balance redox equations. For example, in this case, 2 Ag ions must be reduced for every Cu atom oxidized ... 

Many chemical reactions can be easily balanced. However, balancing oxidation-reduction reactions can be a bit complex. The following general approach can be used in balancing redox reactions. 

Classify the following reactions as oxidation (ox), reduction (red.) or redox reactions. The equations are representative and not balanced. 

Because oxidation and reduction occur simultaneously in all of these reactions, they are referred to as oxidation-reduction reactions. For brevity, we usually call them redox reactions. Redox reactions occur in nearly every area of chemistry and biochemistry. We need to be able to identify oxidizing agents and reducing agents and to balance... 

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