Redox reactions oxidation-reduction identifying

Are these reactions oxidation-reduction reactions Are electrons transferred Simply reading a chemical equation does not always tell us whether oxidation and reduction have occurred, so chemists have developed a numerical system to help identify a reaction as redox. For redox reactions, this system also shows us which element is oxidized, which is reduced, what the oxidizing agent is, and what the reducing agent is. 

Using the electron transfer definition, many more reactions can be identified as redox (reduction-oxidation) reactions. An example is the displacement of a metal from its salt by a more reactive metal. Consider the reaction between zinc and a solution of copper(If) sulphate, which can be represented by the equation... 

The curves relative to the half-reactions intersect at the point corresponding to the formation of the so-called activated complex. The height of the energy barrier of the two redox processes (oxidation, /z0x reduction, hRed) is inversely proportional to the respective reaction rates. Since in this case h0x = hRed, it is immediately apparent that these conditions identify the equilibrium conditions. 

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. 

Determine which of the following balanced net ionic equations represent redox reactions. For each redox reaction, identify the reactant that undergoes oxidation and the reactant that undergoes reduction. 

Chromium(II) is a very effective and important reducing agent that has played a significant and historical role in the development of redox mechanisms (Chap. 5). It has a facile ability to take part in inner-sphere redox reactions (Prob. 9). The coordinated water of Cr(II) is easily replaced by the potential bridging group of the oxidant, and after intramolecular electron transfer, the Cr(III) carries the bridging group away with it and as it is an inert product, it can be easily identified. There have been many studies of the interaction of Cr(II) with Co(III) complexes (Tables 2.6 and 5.7) and with Cr(III) complexes (Table 5.8). Only a few reductions by Cr(II) are outer-sphere (Table 5.7). By contrast, Cr(edta) Ref. 69 and Cr(bpy)3 are very effective outer-sphere reductants (Table 5.7). 

Redox reactions are better defined in terms of the concept of electron transfer. Thus an atom is said to be oxidized if, as the result of a reaction, it experiences a net loss of electrons and is reduced if it experiences a net gain of electrons. This simple definition can be used to identify oxidation or reduction processes at carbon in terms of a scale of oxidation states for carbon based on the electronegativities of the atoms attached to carbon. The idea is to find out whether in a given reaction carbon becomes more, or less, electron-rich. We will use the following somewhat arbitrary rules ... 

The contaminant redox reactions just summarized only occur when coupled with suitable half-reactions involving oxidants or reductants from the environment. In a particular environmental system, these redox agents (along with the physico-chemical factors discussed in section 4.2) collectively determine the nature, rate, and extent of contaminant transformation. Under favorable circumstances, the dominant redox agent(s) can be identified and quantified, thereby providing a rigorous basis for estimating the potential for, and rate of, transformation by abiotic redox reactions. 

Once the relevant oxidation and reduction half-reactions have been identified (e.g., from Tables 16.1-5), they can be combined and balanced to determine the overall reaction for any redox transformation. In generalized form, this can be written... 

Write half-reactions for each of the following redox reactions. Identify each half-reaction as being either oxidation or reduction. 

Once you have a firm grasp on the rules for oxidation numbers and solving problems involving oxidation numbers, you can use oxidation numbers to determine the substance that undergoes a reduction and an oxidation in a redox reaction. You can tell that a substance has been reduced if it has gained electrons (electrons are a reactant). A substance that has been oxidized has lost electrons (electrons are a product). After the substances that have changed oxidation states in a redox reaction are identified, you then write separate half reactions. Half reactions are two separate reactions that show the oxidation and reduction reactions separately. An example follows. 

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 ... 

This imaginary electron machine illustrates the point that the electrons that are involved in redox reactions can come from any source, as long as they are available to transfer. It also points out that reduction, the complimentary process of oxidation, requires something to accept the electrons. These two processes can be identified and separated to help understand redox reactions and balance redox equations. 

A decomposition reaction may or may not also be an oxidation-reduction reaction. You can always identify a redox reaction by determining the oxidation state of each element in each occurrence in the reaction (see the Problem-Solving Tip in Section 4-5). 

Use standard reduction potentials to identify oxidizing and reducing agents in a cell or in a redox reaction... 

Identifying oxidation-reduction reactions and their components Reduction is the gain of an electron by a molecule, atom, or ion, thus decreasing its oxidation number. Oxidation is the loss of an electron, thus increasing the oxidation number of the molecule, atom, or ion. These two processes always occur together in oxidation-reduction reactions, also called redox reactions. Electrons lost by one substance are gained by the other. 

Which of the following reactions are redox reactions In those that are, identify the oxidation and reduction processes. 

---