Acids and Bases 19.1 Introduction Dr. Michael J Passow

Acids and Bases Acids and bases (alkalis) are some of the most important compounds, industrially and internally (biochemically) Common acids include carbonic acid in sodas, citric acids in fruits, acetic acid in vinegar, and hydrochloric acid in your stomach Bases are commonly found in such substances as soaps, cleaning fluids, milk, and blood

Properties of Acids and Bases Acids Sour taste React with some metals to product hydrogen gas (H 2 ) Some carbonates react with acids to release CO 2 Causes blue litmus paper to turn pink Solutions conduct electricity Bases Bitter taste Slippery feel Causes pink litmus paper to turn blue (“blue = base”) Solutions conduct electricity Neutral –neither acid nor base

Ion in Solution Water decomposes in “hydronium ions” H 3 O + (aq) and “hydroxide ions” OH - (aq) H 2 O(l) + H 2 O(l)  H 3 O + (aq) + OH - (aq) Simplified version of “self-ionization”: H 2 O(l)  H + (aq) + OH - (aq) (“Pure water” is always neutral, and very rare.)

Types of Acids and Bases Arrhenius Acid contains H and ionizes to form H + in solutions HCl(g)  H + + Cl - Base contains OH and dissociates to produce OH - in solutions NaOH  Na + + OH - Bronsted-Lowry Acid donates H + (hydrogen-ion donor) Base accepts H + (hydrogen-ion donor) HX + H 2 O  H 3 O + + X - acid base

Conjugate Acids and Bases Conjugate acids Produced when a base accepts a H + from an acid Conjugate bases What results when an acid donates a H + to a base HX + H 2 O  H 3 O + + X - (acid) (base) (conjugate acid) (conjugate base) NH 3 + H 2 O  NH OH - (base) (acid) (conjugate acid) (conjugate base) (H 2 O and other substances that can act as both acids and bases are said to be amphoteric)

Carbonic acid and carbonates CO 2, O 2, and H 2 O in air may form carbonic acid H 2 CO 3. When this “acid rain” encounters carbonates (limestones, marbles, cement), it may dissolve the substance When liquid evaporates, deposits may form Stalactites hang tightly Stalagmites grow up mightily