1.18.1. General Information and Nomenclature.
As you are fully expected to know by now, salts are compounds comprising one or more metal atoms and one or more acid remainders. You are also expected to know the nomenclature of salts. To name a salt, one needs to name the metal first and then the acid remainder (Table 2 in section 1.12
). As is the case with oxides and bases, if a metal can be in more than one state of valence, the latter should be specified as a Roman numeral in parentheses after the name of the metal. According to this rule, CuBr is called copper (I) bromide and CuBr2
copper (II) bromide. However, if a metal that can exhibit more than one valence forms only one salt with a particular acid remainder, there is no need to specify the valence in the name of the salt. For example, the valence of copper can be 1 and 2. In principle, one would expect copper to form two fluoride salts, CuF and CuF2
. Of these two, however, only CuF2
exists. Consequently, we name CuF2
copper fluoride, not copper (II) fluoride. Similarly, CuI does exist, whereas CuI2
does not. For this reason, the correct name for CuI is copper iodide, not copper (I) iodide.
Numerous salts occur in nature both as solid minerals and in solution, such as sea water and mineral water. Among the most common native salts are NaCl and carbonates, sulfates, and chlorides of potassium, calcium, and magnesium. Calcium carbonate is the main component of such highly important minerals as limestone, marble, and chalk. The mineral calcite is essentially pure CaCO3
, and so is the chicken eggshell. 1.18.2. Preparation of Salts.
Since many salts are commercially available, there is rarely a need to make simple salts in the laboratory. If necessary, salts can be prepared by a number of reactions, including between (i) a base and an acid (neutralization); (ii) a base and an acidic oxide; (iii) an acid and a basic oxide; and (iv) a metal and an acid. Insoluble or poorly soluble salts are also conveniently prepared by a variety of exchange reactions between a soluble salt and another soluble salt, an acid, or a base (Figure 1-87).