Chapter 16 Acids and Bases Properties Arrhenius Definitions Bronsted-Lowry Definitions

Properties of Acids

Properties of Bases

Svante Arrhenius Acids and Bases BASES: yield OH - ions in water, substances that increase the OH - ion concentration when dissolved in water ACIDS: yield H + ions in water, substances that increase the H + ion concentration when dissolved in water

Bronsted-Lowry Definition Broadens substances that be categorized as Acid or Base Involves the TRANSFER of H + ions

Water to Hydronium Chemists use H + and H 3 O + interchangeably Considered the “acidic” form of water Amphoteric = react as an acid or base Amphiprotic = can donate and accept H + ion Watch This Tutorial

HCl (aq) + H 2 O (l)  Cl - (aq) + H 3 O + (aq) ACID BASE CONJUGATE BASE CONJUGATE ACID ACID = proton donor BASE = proton acceptor

Practice Naming/Writing Conjugate Pairs ACID +BASE  CONJUGATE BASE + CONJUGATE ACID HClH2OH2OH3O+H3O+ Cl - H2OH2ONH 3 OH - NH 4 + H 2 SO 4 NH 3 HSO 4 - NH 4 +

Strengths of Acids and Bases The stronger an acid, the weaker it’s conjugate base. INVERSE relationship Table p STRONG acids completely ionize in water, have neglible conjugate bases. 2. WEAK acids partially ionize in water, have weak base conjugates. 3.NEGLIBLE acids incapable of protonation (do not dissociate), thus have strong base conjugates.

In every acid-base reaction, equilibrium favors transfer of proton from the stronger acid to the stronger base to form the weaker acid and the weaker base. Acid-Base Equilibrium In any acid-base reaction, the equilibrium will favor the reaction that moves the proton to the stronger base.

QUESTION? Predict whether equilibrium lies to the left or to the right. LEFT would be K c < 1 RIGHT would be K c > 1 ANSWER: Examine the two bases on table (forward and reverse rxns) H 2 O and Cl - H 2 O is a stronger base than Cl -, forward rxn favored, Equilibrium lies to right K c > 1 HCl (aq) + H 2 O (l)  Cl - (aq) + H 3 O + (aq)

In any acid-base reaction, the equilibrium will favor the reaction that moves the proton to the stronger base. HC 2 H 3 O 2 (aq) + H 2 O (l) H 3 O + (aq) + C 2 H 3 O 2 - (aq) QUESTION? Predict whether equilibrium lies to the left or to the right. LEFT would be K c < 1 RIGHT would be K c > 1 Acetate is a stronger base than H 2 O, so the equilibrium favors the left side (K < 1)