Acids and Bases
Acids donate protons (H⁺) while bases accept them; the strength of an acid depends on its molecular structure.
Acids and Bases
Brønsted–Lowry Definition
- Acid — donates a proton (H⁺)
- Base — accepts a proton
Strong vs Weak Acids
A strong acid completely dissociates in water:
HCl → H⁺ + Cl⁻
H₂SO₄ → 2 H⁺ + SO₄²⁻
A weak acid partially dissociates:
CH₃COOH ⇌ H⁺ + CH₃COO⁻
Sulfuric Acid — A Case Study
Sulfuric acid (H₂SO₄) is a strong diprotic acid — it can donate two protons. The first dissociation is complete, while the second is partial:
- H₂SO₄ → H⁺ + HSO₄⁻ (strong)
- HSO₄⁻ ⇌ H⁺ + SO₄²⁻ (weak, Ka = 0.01)
The central sulfur atom's high oxidation state (+6) strongly polarises the O–H bonds, making proton donation favourable.
Related molecules: Sulfuric Acid
Learn more: Chemical Bonding