10.0: Prelude to Acids and Bases One of the most concentrated acids in the body is stomach acid, which can be approximated as a 0.05 M hydrochloric acid solution. Special cells in the stomach wall secrete this acid, along with special enzymes, as part of the digestion process. In a laboratory, a 0.05 M solution of hydrochloric acid would dissolve some metals. How does the stomach survive the presence of such a reactive acid? 10.1: Acids and Bases Definitions Arrhenius acid: a compound that increases the concentration of hydrogen ion (H+) in aqueous solution; Arrhenius base: a compound that increases the concentration of hydroxide ion (OH−) in aqueous solution. the reaction of an acid and a base 10.2: Acid and Base Strength Acids and bases can be strong or weak depending on the extent of ionization in solution. Most chemical reactions reach equilibrium at which point there is no net change. The pH scale is used to succinctly communicate the acidity or basicity of a solution. 10.3: Water as Both an Acid and a Base Water molecules can act as both an acid and a base, depending on the conditions. 10.4: Measuring Acidity in Aqueous Solutions- The pH Scale 10.5: Working with pH 10.6: Buffers A buffer is a solution that resists sudden changes in pH. 10.7: Titration