Chapter 14 Acids and Bases

Vocabulary to Know Arrhenius acid/base: donator of hydrogen/hydroxide ion Bronsted-Lowry acid/base: hydrogen donator/acceptor Example: HCl + H2O -> H3O+ + Cl- H3O+ = hydronium ion (frequently seen as H+(aq)) Lewis acid/base: electron pair acceptor/donor Example: H+ + NH3 -> NH4+ Example: H+ + OH- -> H2O Example BF3 + NH3 -> BF3NH3 Example: Ni2+ + 6NH3 -> Ni(NH3)62+

Summary Table

General Reaction Dissolving an Acid in Water HA(aq) + H2O(l) <-> H3O+(aq) + A-(aq) Acid Base Conjugate A. C.B. Conjugate Base: Everything left of the acid molecule after the proton is lost Conjugate Acid: Formed when the proton is transferred to the base Conjugate Acid-Base Pair: Two substances related to each other by the donating and acceping of a single proton (HA & A- and H2O & H3O+)

Example Write the dissociation reaction for each of the following acids in water, and identify the conjugate acid-base pairs: Formic acid (HCOOH) Perchloric acid (HClO4)

Note… HA(aq) + H2O(l) <-> H3O+(aq) + A-(aq) Acid Base Conjugate A. C.B. H2O (base) and A- (conjugate base) are competing for the proton. Whichever is the stronger base will dominate the equilibrium position. If H2O is a stronger base, equilibrium RIGHT If A- is stronger, equilibrium LEFT

Acid Dissociation Constant (Ka) When a proton is removed from HA to make A-… HA(aq) + H2O(l) <-> H3O+(aq) + A-(aq) Ka = [H3O+] [A-] = [H+] [A-] [HA] [HA] *even though water (l) is not included in this expression, it is still necessary for the reaction to occur

Examples Write the dissociation (ionization) reaction (omitting water) for each of the following acids: Hydrochloric acid (HCl) Acetic Acid (HC2H3O2) The ammonium ion (NH4+) The anilinium ion (C6H5NH3+) Write the formula for the acid dissociation constant for each of the reactions