Types of Chemical Reactions
...actions (a chemical change accompanied by a gain of electrons) and Oxidation reactions (a chemical change accompanied by a loss of electrons). Redox reactions involve electron transfer from one atom/molecule to another. The reactant which loses the electron is oxidized and conversely, the reactant that gains the electron is reduced. The equation Zn + 2HCl à ZnCl2 + H2 is an example of a redox reaction, because zinc metal is oxidized to Zn+2 and H+ is reduced to H2 gas. A noticeable physical change is color change. In most of our redox experiments, the reactants either changed color or changed the color of the solution it was added to. Precipitation reactions involve a solid product called a precipitate being formed from a reaction in the solution. This happens when water soluble reactants form one or more products which are insoluble in water. For example, the formation of stalactites and stalagmites in caverns resulted from the reaction Ca(HCO3)2 à CaCO3 + CO2 + H2O where CaCO3 is not water soluble. The physical change, which is an outcome of these types of reactions, is that the solution usually turns a milky white color with chunks in it that are called preci...