1. Acids & Bases
Section Notes

2. Properties of Acids Taste sour (eg: citric acids, acetic acid)
React with metals
Causes blue litmus to turn pink
Aqueous solutions conduct electricity

3. Properties of Bases Taste bitter Feel slippery (eg: soap)
Causes pink litmus to turn blue
Aqueous solutions conduct electricity

4. H2O(l) + H2O(l)  H3O+(aq) + OH-(aq)
Ions in solution
All water solutions contain H+ & OH-
Acidic solution – contains more H+
Basic solution – contains more OH-
Neutral solution – contains equal H+ & OH-
Water undergoes self-ionization
H2O(l) + H2O(l)  H3O+(aq) + OH-(aq)
H3O+ and H+ used interchangeable to represent a hydrogen ion
Pure water is neutral b/c H+ = OH-

5. Arrhenius Acids & Bases
Swedish chemist Svante Arrhenius (1887) first proposed how acids & bases form
Arrhenius model
Acids – produce H+ in aq. soln.
HCl(g)  H+(aq) + Cl-(aq)
Bases – produce OH- in aq. soln.
NaOH(s)  Na+(aq) + OH-(aq)
Shortcoming: does not explain all bases (eg: NH3 = base)

6. Brønsted-Lowry Model
Danish chemist Johannes Brønsted & English chemist Thomas Lowry proposed more inclusive model
Brønsted-Lowry model
Acid – H+ donor
Base – H+ acceptor
Every Brønsted-Lowry interaction involves conjugate acid-base pairs
Conjugate acid – species produced when a base accepts H+ from an acid
Conjugate base – species produced when an acid donates H+ to a base
HX H2O  H3O X-
acid base conjugate conjugate
acid base

7. You try…
Identify the conjugate acid/base pairs in each of the following reactions.
NH4+(aq) + OH-(aq)  NH3(aq) + H2O(l)
HBr(aq) + H2O(l)  H3O+(aq) + Br-(aq)
Amphoteric – substance that can act as both an acid and a base
CO32-(aq) + H2O(l)  HCO3-(aq) + OH-(aq)
HSO4-(aq) + H2O(l)  H3O+(aq) + SO42-(aq)

8. Monoprotic and Polyprotic Acids
Monoprotic – contains 1 ionizable hydrogen atom (HCl)
Diprotic – contains 2 ionizable hydrogen atoms (H2SO4)
Triprotic – contains 3 ionizable hydrogen atoms (H3PO4)
Steps for ionization of a polyprotic acid:
H3PO4
H2Se
H2SO3

9. Strength of Acids
Strong acids – ionize completely in water (good conductors)
HCl + H2O  H3O+ + Cl-
Rxn goes to completion
Denoted by single arrow
Weak acids – ionize only partially in water (p. 602)
HC2H3O2 + H2O  H3O+ + C2H3O2-
Reversible rxn (double arrow)
Equilibrium established

10. Strength of Bases
Strong base – dissociates entirely into metal ions & hydroxide ions
NaOH  Na+ + OH-
Weak base – ionizes only partially to form conjugate acid & hydroxide ion
CH3NH2 + H2O  CH3NH3+ + OH-