7.4: Solution Equations: Introduction

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Learning Objectives

Define solution equation.

As stated in Section 7.1, a solution is a uniform blend of two or more elements or compounds that are not bonded together and, therefore, can be separated from one another. Additionally, while the physical forms of the solvent and solutes that are present in a solution are transformed during the dissolving process, the chemical compositions and properties of these substances are not. Therefore, solvation, which is often a reversible process, is classified as a physical change. Furthermore, since, by definition, the solvent and solutes that are present in a solution do not react with one another, the preparation of a solution does not qualify as a chemical reaction and, consequently, cannot be represented in a chemical equation. Instead, the physical changes that occur during the solvation process are symbolically represented using a solution equation.

As will be discussed in greater detail in the following three sections of this chapter, solutes can be classified as non-electrolytes, strong electrolytes, or weak electrolytes, based on the degree to which they dissociate, or separate, during the solvation process. As each of these electrolytes is generated through a unique solvent/solute interaction, the solution equations that represent their dissociations must also be distinctive. Finally, because many different chemicals can be used to prepare a solution, the identities of the specific solvent and solute that are involved in a solvation process must be incorporated into the solution equation that is written to represent their interaction. Therefore, a solution equation pattern, which symbolically represents the dissociative behavior of a generic solute and, therefore, can be modified to reflect the chemical composition of a particular solution, will be presented and applied for each type of electrolyte that is listed above.