Acids and Bases

Acids An acid is compound that produces hydrogen ions (H+) when dissolved in water. Naming acids If anion ends in –ide, the acid name begins w/ hydro- and ends w/ -ic. Example HCl Hydrochloric Acid If anion ends in –ite, the acid name is the stem of the anion w/ the suffix –ous. Example H2SO3 Sulfurous Acid

Cont. If the anion ends in –ate, the acid name is the stem of the anion w/ the suffix –ic. Example HNO3 Nitric Acid

Bases A base is a compound that produces hydroxide ions (OH-) when dissolved in water. Naming bases Bases are named the same as any other ionic compound. Example NaOH Sodium hydroxide

Self-Ionization of Water A water molecule that gains a hydrogen ion is called hydronium (H3O+) A water molecule that loses a hydrogen ion is called hydroxide (OH-) H2O(l) H+(aq) + OH-(aq)

Cont. The rxn in which 2 water molecules produce ions is called the self-ionization of water. In pure water the concentration of hydrogen ions and the concentration of hydroxide ions are each 1.0 x 10-7 M If H+ decreases, then OH- increases, and vice versa.

Ion-product Constant for Water Kw Kw = [H+] x [OH-] = 1.0 x 10-14M When some substances dissolve in water they release hydrogen ions (Acids) When some substances dissolve in water they release hydroxide ions (Bases)

pH Ranges from 0-14, neutral is 7, 0 is strongly acidic, and 14 is strongly basic. pH = -log [H+] Example of neutral pH [H+] = pH = -log (1 x 10-7M) pH = 7.0

Measuring pH Acid-Base indicators – indicators are acids or bases that undergo dissociation in a known pH range. When it undergoes dissociation there is a color change Examples Thymol blue Bromthymol blue Phenolphthalein pH meters - record electric activity using a millivoltmeter.