An acid is a substance that releases hydrogen ions (H+) in an aqueous solution. A base is a substance that releases hydroxide ions (OH–) in an aqueous solution.
A strong acid is a substance that fully dissociates in water to produce H+ (Eg. HCl, H2SO4) A strong base is a substance that fully dissociates in water to produce OH– (Eg. NaOH)
Example:
Hydrochloric acid (HCl) HCl + H2O → Cl– + H3O+
Sulfuric acid (H2SO4) H2SO4 + H2O → HSO4– + H3O+ HSO4– + H2O ⇌ SO42- + H3O+
Sodium Hydroxide (NaOH) NaOH + H2O → Na+ + OH– + H2O
A weak acid is a substance that partially dissociates in water to produce H+ (Eg. CH3COOH, H2CO3 , H3PO4) A weak base is a substance that partially dissociates in water to produce OH– (Eg. NH3)
Example:
Acetic acid (CH3COOH) CH3COOH + H2O ⇌ CH3COO– + H3O+
Carbonic acid (H2CO3) H2CO3 + H2O ⇌ HCO3– + H3O+ HCO3– + H2O ⇌ CO32- + H3O+
Phosphoric acid (H3PO4) H3PO4 + H2O ⇌ H2PO4– + H3O+ H2PO4– + H2O ⇌ HPO42- + H3O+ HPO42- + H2O ⇌ PO43- + H3O+
Ammonia (NH3) NH3 + H2O ⇌ NH4+ + OH–
Arrhenius acid-base theory
Arrhenius acid is a substance which increases the concentration of hydronium ions/H3O+ (Eg. HCl) Arrhenius base is a substance which increases the concentration of hydroxide ions/OH– (Eg. NaOH)
Example: HCl + H2O → H3O+ + Cl– NaOH → Na+ + OH–
BrØnsted-Lowry acid-base theory
A BrØnsted-Lowry acid is a proton donor (Eg. HCl) A BrØnsted-Lowry base is a proton acceptor (Eg. NH3)
Example: HCl + NH3 → NH4Cl
Lewis acid-base theory
A lewis acid is an electron-pair acceptor (Eg. BF3) A lewis base is an electron-pair donor (Eg. :NH3)
Example: :NH3 + BF3 → NH3BF3