Strength of Acids
and Bases
Electrical Conductivity
 Acidic and basic solutions conduct
electricity.
Strengths of Acids
 Acids that completely ionize (dissociate) are called
strong acids.
Strong acids produce a strong electric
current = strong electrolyte
HCl(aq) +H2O(l)  H3O+(aq) + Cl(aq)
Strengths of Acids
 Weak acids partially ionize in solutions = weak
electrolyte
 Produce fewer ions and cannot conduct electricity as
efficiently as strong acids
 HC2H3O2(aq) +H2O(l)  H3O+(aq) + C2H3O2− (aq)
Six Strong Acids
1. Hydrochloric acid: HCl
2. Hydrobromic acid: HBr
3. Hydroiodic acid: HI
4. Sulfuric acid: H2SO4
5. Nitric acid: HNO3
6. Perchloric acid: HClO4
These acids completely dissociate in water.
Strength of Bases
 Strong bases dissociate entirely into
metal ions and hydroxide ions.
 Weak bases ionizes only partially in dilute
aqueous solution
Eight Strong Bases
1.
2.
3.
4.
5.
6.
7.
8.
Lithium hydroxide: LiOH
Sodium hydroxide: NaOH
Potassium hydroxide: KOH
Rubidium hydroxide: RbOH
Cesium hydroxide: CsOH
Calcium hydroxide: Ca(OH)2
Strontium hydroxide: Sr(OH)2
Barium hydroxide: Ba(OH)2
These bases completely dissociate in water.
Acid/Base Strength vs.
Concentration
 Do not get acid/base strength confused with
concentration.
 Acid/base strength is based on the ability to
dissociate.
 Concentration is based on how much is dissolved
in solution.
 You can have a strong dilute acid – the acid
completely dissociates, but there is not much
acid dissolved in solution
Acid Ionization Constant
 Acid ionization constant (Ka) is the value
of the equilibrium constant
expression(Keq) for the ionization of a
weak acid.
 Large Ka strong acid
 Small Ka weak acid
Base Ionization Constant
 The base ionization constant (Kb) is the
value of the equilibrium constant
expression (Keq) for the ionization of a
base
 Large Kb strong base
 Small Kb weak base
Write the ionization equation and acid
ionization constant (Ka) expressions
for the acid HF
If you calculate Ka, it will be a weak acid so it will have a
double arrow. Add it to water.
HF + H2O(l)  H3O+ + F(A)
(B)
(CA)
(CB)
Ka = [H3O+ ] × [F-]
[HF]
Leave out liquids and solids in Keq
Write the ionization equation and base
ionization constant (Kb) expressions
for the base NH3
If you calculate Kb, it will be a weak base so it will have a
double arrow. Add it to water.
NH3 + H2O(l)  NH4+ + OH(B)
(A)
(CA)
(CB)
Kb = [NH4 + ] × [OH-]
[NH3]
Leave out liquids and solids in Keq