• 1.0. MODULE 1: TERMINOLOGY/HOMEOSTASIS
  • 2.0. MODULE 2: INORGANIC CHEMISTRY
  • 3.0. MODULE 3: ORGANIC CHEMISTRY
  • 4.0. MODULE 4: THE CELL
  • 5.0. MODULE 5: CELL MEMBRANES-STRUCTURE AND TRANSPORT
  • 6.0. MODULE 6: NERVOUS SYSTEM ORGANIZATION
  • 7.0. MODULE 7: SKELETAL MUSCLE
  • 8.0. MODULE 8: METABOLISM
  • 9.0. MODULE 9: CONTROL OF BODY MOVEMENT
  • 10.0. MODULE 10: THE AUTONOMIC NERVOUS SYSTEM
  • 11.0. MODULE 11: THE BRAIN
  • 12.0. MODULE 12: SPECIAL SENSES
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  • Translations
  • 2.3.1

    Acids and Bases

    In pure water at 25o C, the concentration of H+ is always equal to the concentration of OH-. Both have a concentration of 1.0 x 10-7 Molar. (Placing the symbol for a chemical in brackets [H+] is chemical shorthand for “concentration of.” Therefore, [H+] is read “the concentration of hydrogen ion.”) If we add a substance that results in an increase in [H+], we say that substance is an acid. If we add a substance that results in a decrease in [H+], we say that substance is a base. An acid is any substance that, when added to an aqueous solution, increases the [H+] of the solution, and a base is any substance that, when added to an aqueous solution, decreases the [H+] of the solution. A common acid, for example, is hydrochloric acid, HCl. When HCl reacts with water, it dissociates into an H+ and a chloride ion (Cl-), thus increasing the [H+]. HCl is considered a strong acid because when placed in water, it completely dissociates into its two ions.

    HCl --> H+ + Cl-

    A weak acid, such as acetic acid (CH3COOH), dissociates into H+ and CH3COO-. However, most remain as acetic acid, and there is a chemical equilibrium between the CH3COOH and the H+ + CH3COO-.

    CH3COOH <-- --> H+ + CH3COO-

    An example of a base is ammonia (NH3), which will combine with H+ to form an ammonium ion (NH4+), thus removing H+ from the solution.

    NH3 + H+ --> NH4+

    Another common base is sodium hydroxide (NaOH). How is this a base? When it dissolves, it dissociates into a sodium ion (Na+) and OH-, no change in [H+], right? However, the OH- will combine with Hto form water, thus removing H+ from the solution.

    NaOH --> Na+ + OH-

    H+ + OH- --> H2O

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    Access it online or download it at https://books.byui.edu/bio_264_anatomy_phy_I/231__acids_and_bases.