Question

Define:

1) Oxidation reaction

2) reduction reaction

3) neutralization reaction

4) precipitation reaction

Answer 1

Oxidation and Reduction
Oxidation and reduction reactions usually involve the transfer of electrons. A gain of electron is called reduction, and a loss of electron is oxidation. Since electrons can neither be created nor destroyed a gain of electrons by one species must be accompanied by a loss of another species. Thus, oxidation reactions are always accompanied by reductions, and reactions of this type are called redox reactions. These reactions are the basis for battery or Daniel cell operations.

Before the realization of electron transfers, reactions with oxygen were called oxidation reaction, and reactions with hydrogen or with base-forming elements such as metals were called reduction reactions. However, the more modern definition will be used in our discussion of chemistry.

There are many redox reactions, and balancing redox reaction equation is a basic skill for an educated person. A unit will be devoted to balance redox reaction equations in this course. This type of reactions may belong to types mentioned earlier. Please identify the species that are oxidized and reduced in the following reactions,

Zn + H2SO4 = ZnSO4 + 2 H2; (zinc oxidized)
2 HCl + F2 = 2 HF + Cl2 (flourine reduced)
2 Na + H2O = 2 NaOH + H2 (hydrogen reduced)
2 Al + Fe2O3 = 2 Fe + Al2O3
2 HgO = 2 Hg + O2 (oxygen oxidized)
2 KClO3 = 2 KCl + 3 O2 (chlorine reduced)
C2H5OH + O2 = CO2 + H2O


Neutralization Reaction


Acid and Bases Many substances are known as acids and bases In the HandbookMenu, some properties of acids and bases are given in two tables and you may click them to find out their names and formulas. Reactions between acids and bases are called acid-base reactions. Some of them are often called neutralization reactions. However, the concepts of acids and bases have been generalized and much more discussion can be found in modules or units in Chem123/125. Thus, acid-base reactions are further subdivided into other types. A few examples are given below, HCl + NaOH = NaCl + H2 . . . neutralization

Precipitation
Solids appear when two solutions are mixed if the products formed are not soluble. The solids are called precipitates, and such reactions are called precipitation reactions. In reaction equations, we use (s) to represent the formation of a solid or precipitate (ppt). AgNO3 + NaCl = NaNO3 + AgCl(s)
PbNO3 + KI = PbNO3 + PbI(s)

Precipitation reactions take place in solutions, and ions exchange in these reactions. Thus, they are often called exchange reactions or metathesis reactions.