Acids and Bases—An
Introduction
Arrhenius Definition
 Acids
 Produce H+ ions when dissolved in water
 Ionize into H+ ions and negative ion
 (Ex. HCl, HBr)
 Bases
 Produce OH- ions when dissolved in water
 Ionize into OH- ion and positive ion
 (Ex. NaOH, Mg(OH)2 )
 Does not apply to ALL acids and bases! !
Examples
 HCl
 NaOH
Bronsted-Lowry Definition
 Focus on hydronium (H3O+) ion
 Acids
 H+ ion donator/proton donator
 Produces hydronium ion
 Donates hydrogen ions to molecule acting as base
 Bases
 H+ ion acceptor/proton acceptor
 Accepts hydrogen ions from donating compound
 Contains compounds with NONBONDING valence
electrons to accept proton
Examples
 CH3CO2H + H2O  CH3CO2- +
H3O+
 C6H5NH2 + HNO3  C6H5NH3+ + NO3-
Lewis Definition
 Deals with electron pairs
 Acids
 Electron pair acceptor
 Bases
 Electron pair donor
 Covalent bond forms between acid and base
 ALL Bronsted-Lowry bases are Lewis bases, NOT all
Bronsted-Lowry acids act like Lewis acids
Example
 CaO +
SO2  CaSO3
Monoprotic vs. Polyprotic
Acids
 Monoprotic acids
 Acid contains only ONE hydrogen ion that can be
donated
 Polyprotic acids
 More than one hydrogen ion can be donated from acid
 Amphiprotic
 Chemical compound acting as either acid or base
Conjugate Acids/Bases
 Acids and bases are related to each other through the
addition/loss of hydrogen ions
 Conjugate acid-base pairs
 Acids produce conjugate bases
 Bases produce conjugate acids
Conjugate Examples
 HClO2 + KOH  H2O + KClO2
 HNO3 + NH3  NH4+ + NO3-
Strength of Acids and Bases
 Based on the concentration of H+ or OHions in a solution.
 Strong Acids/Bases: completely
dissociate into ions in a solution.
 Weak Acids/Bases: do NOT completely
dissociate into ions in a solution.
Strong Acid Example: HCl
Weak Acid Example:
CH3CO2H
“BIG 6”---Strong Acids
(Know them!!)
 HClO4
 HI
 HCl
 HNO3
 HBr
 H2SO4
Strong Bases
(Know them!!)
 Group I metal hydroxides (NaOH, KOH, etc.)
 Soluble/Slightly soluble Group II metal hydroxides (
Ca(OH)2, Sr(OH)2, Ba(OH)2 )
 Soluble metal oxides ( Li2O, Na2O, K2O, CaO )
Conjugate Acid/Base Strength
 Stronger the acid, the weaker the conjugate base
 Stronger the base, the weaker the conjugate acid
 Weak acids/bases have strong conjugate bases/acids
 Acid/Base reactions favor direction from
 Stronger-----------weaker of each conjugate acid/base