Single-Replacement Oxidation-Reduction Redox Reactions

Single-Replacement Oxidation-Reduction (Redox) Reactions 

Remove the spectator ions to arrive at the net ionic equation. Check for charge and atom balance. 

The six plus charge on the left balances the six plus charge on the right. Three Mg and two Fe on each side give atom balance. 

In this case, the net ionic equation tells you that magnesium metal is changed to magnesium ions in solution while the opposite process occurs for iron. The iron ions that were in solution were changed to iron atoms, which collectively form solid iron. The chloride ions in the solution are unchanged while the metals react, and thus they do not appear in the net ionic equation. 

Go to http //now.brookscole.com/ cracoliceSe and click Coached Problems for a tutorial on Writing Net Ionic Equations. 

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Section 9.5 Single-Replacement Oxidation-Reduction (Redox) Reactions... 

These reactions are part of a larger category of reactions known as redox reactions (redox is short for oxidation-reduction). Sometimes these are called displacement reactions. These are chemical reactions in which atoms of one element replace the atoms of a second element in a compound. A general equation for a single-replacement reaction involving a metal (A), replacing a metallic cation in solution (B) is ... 

Redox reactions are not limited to single replacement reactions. They really describe a wide variety of reactions, but each shares the common theme of involving an oxidation and a reduction. An oxidation occurs when a substance loses electrons and becomes more positively charged. Earlier in the book we discussed a similar phenomenon in the formation of ionic compounds. Substances don t just lose electrons for no reason. They lose electrons because another substance takes them. When a substance acquires additional electrons and becomes more negatively charged, it is called a reduction. An oxidation cannot take place without a reduction, so these processes must occur simultaneously. These reactions describe the simultaneous oxidation and reduction of materials, which has earned them the name oxidation-reduction reactions. 

An oxidation-reduction reaction is one in which electrons are transferred from one reactant to another. They are often called redox reactions for short. Oxidation is the loss of one or more electrons by a species. The species losing electrons is oxidized. Reduction is the gain of one or more electrons by a species, and that species is reduced. Oxidation and reduction always occur simultaneously. The single-displacement reaction of copper metal with silver nitrate solution is both a single replacement reaction and an oxidation-reduction reaction. 

Many elements are capable of replacing ions of other elements in aqueous solution. This is one kind of oxidation-reduction reaction, or redox reaction. The equation for such a reaction looks as if one element is replacing another in a compound. It is a single-replacement equation. These reactions are sometimes called singlereplacement reactions. The general equation is... 

Fig. 4 Reaction pathways for superoxide dismutases and superoxide reductases. Shown in black are the two possible pathways leading to oxidation of the active site by superoxide, producing peroxide this half of the catalytic cycle is common to SOR and SOD. Shown in gray is the re-reductive path specific to SOD, and which in SOR is replaced by a single-electron transfer from the specialized redox protein, rubredoxin. M may be Fe (n = 2, in SOR, or in SOD), Ni, Mn (n = 2, in SOD), or Cu (n = 1, in SOD)...

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