Determine if a salt produces an acidic or a basic solution.
Strong and Weak Acids
Strong Acid: An acid that dissociates 100% into ions (e.g., HCl → H⁺ + Cl⁻).
Weak Acid: An acid that does not dissociate completely in solution (e.g., HC₂H₃O₂ ⇌ H⁺ + C₂H₃O₂⁻).
There are very few strong acids. If an acid is not listed as a strong acid, it is a weak acid, regardless of the percentage ionization.
Examples of Strong Acids
HCl (Hydrochloric acid)
HBr (Hydrobromic acid)
HI (Hydroiodic acid)
HNO₃ (Nitric acid)
H₂SO₄ (Sulfuric acid)
HClO₃ (Chloric acid)
HClO₄ (Perchloric acid)
Strong and Weak Bases
Strong Base: A base that is 100% ionized in solution.
Weak Base: A base that is less than 100% ionized in solution. Bases that do not contain hydroxide ions in their formula, such as NH₃, are typically weak bases.
Examples of Strong Bases
LiOH (Lithium hydroxide)
NaOH (Sodium hydroxide)
KOH (Potassium hydroxide)
RbOH (Rubidium hydroxide)
CsOH (Cesium hydroxide)
Mg(OH)₂ (Magnesium hydroxide)
Ca(OH)₂ (Calcium hydroxide)
Sr(OH)₂ (Strontium hydroxide)
Ba(OH)₂ (Barium hydroxide)
Identifying Strong and Weak Acids/Bases
A chemical listed in the table of strong acids and bases is strong.
If not listed, it is considered weak.
Example 14.7.1: Identifying Strong and Weak Acids and Bases
HCl: Strong acid
Mg(OH)₂: Strong base
C₅H₅N (Pyridine): Weak base (because it does not contain OH ions)
Exercise Example
RbOH: Strong base
HNO₂: Weak acid
Base Ionization Example
Ca(OH)₂ dissociates as follows:
Ca(OH)₂ → Ca²⁺ + 2OH⁻
As it is a strong base, it dissociates 100%.
Exercise Example
HN₃ dissociates as follows:
HN₃ ⇌ H⁺ + N₃⁻
Does not dissociate 100% because it is a weak acid.
Key Takeaways
Strong acids and bases are 100% ionized in aqueous solution.
Weak acids and bases are less than 100% ionized.
Salts of weak acids or bases can influence the acidity or basicity of their solutions.
Contributions & Attributions
Content shared under CK-12 license by Marisa Alviar-Agnew & Henry Agnew.