5.1: Prelude to Solutions Solutions are homogenous mixtures of two or more compounds. In the case of liquid phase solutions, the solvent is typically the compound in greater quantity, and it is in a liquid state, and the solute is lesser quantity, where the solute is dissolved into the solvent. In aqueous solutions, water is the solvent, even if it is in lesser quantities, and in this class, we will be dealing mostly with aqueous solutions. The solute can be of a different phase than the solvent. 5.2: Solution Concentration and Solution Stoichiomentry Solution concentrations are typically expressed as molarities and can be prepared by dissolving a known mass of solute in a solvent or diluting a stock solution. The concentration of a substance is the quantity of solute present in a given quantity of solution. Concentrations are usually expressed in terms of molarity, defined as the number of moles of solute in 1 L of solution. 5.3: Solution Stoichiometry 5.4: Types of Aqueous Solutions and Solubility Electrolytic solutions are those that are capable of conducting an electric current. A substance that, when added to water, renders it conductive, is known as an electrolyte. A common example of an electrolyte is ordinary salt, sodium chloride. Solid NaCl and pure water are both non-conductive, but a solution of salt in water is readily conductive. A solution of sugar in water, by contrast, is incapable of conducting a current; sugar is therefore a non-electrolyte. 5.5: Precipitation Reactions A complete ionic equation consists of the net ionic equation and spectator ions. Predicting the solubility of ionic compounds gives insight into feasibility of reactions occuring. The chemical equation for a reaction in solution can be written in three ways. The overall chemical equation shows all the substances in their undissociated forms; the complete ionic equation shows substances in the form in which they actually exist in solution; and the net ionic equation omits all spectator ions. 5.6: Representing Aqueous Reactions- Molecular, Ionic, and Complete Ionic Equations The chemical equation for a reaction in solution can be written in three ways. The overall chemical equation shows all the substances present in their undissociated forms; the complete ionic equation shows all the substances present in the form in which they actually exist in solution; and the net ionic equation is derived from the complete ionic equation by omitting all spectator ions, ions that occur on both sides of the equation with the same coefficients. 5.7: Acid-Base Reactions An acidic solution and a basic solution react together in a neutralization reaction that also forms a salt. Acid–base reactions require both an acid and a base. In Brønsted–Lowry terms, an acid is a substance that can donate a proton and a base is a substance that can accept a proton. Acids also differ in their tendency to donate a proton, a measure of their acid strength. The acidity or basicity of an aqueous solution is described quantitatively using the pH scale. 5.8: Gas Evolution Reactions A gas evolution reaction is a chemical process that produces a gas, such as oxygen or carbon dioxide. 5.9: Oxidation-Reduction Reactions Oxidation–reduction reactions are balanced by separating the overall chemical equation into an oxidation equation and a reduction equation. In oxidation–reduction reactions, electrons are transferred from one substance or atom to another. We can balance oxidation–reduction reactions in solution using the oxidation state method, in which the overall reaction is separated into an oxidation equation and a reduction equation. The outcome of these reactions can be predicted using the activity series.