acids and bases 19.1 introduction dr. michael j passow
TRANSCRIPT
Acids and Bases
19.1 IntroductionDr. 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 (H2)• Some carbonates react with
acids to release CO2
• 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” H3O+ (aq) and “hydroxide ions” OH-(aq)
H2O(l) + H2O(l) H3O+ (aq) + OH-(aq)
Simplified version of “self-ionization”:H2O(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 + H2O H3O+ + 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 + H2O H3O+ + X-
(acid) (base) (conjugate acid) (conjugate base)
NH3 + H2O NH4+ + OH-
(base) (acid) (conjugate acid) (conjugate base)
(H2O and other substances that can act as both acids and bases are said to be amphoteric)
Carbonic acid and carbonates
• CO2, O2, and H2O in air may form carbonic acid H2CO3.
• 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