• Robert Boyle’s Approach (17th Century)
  • Acids: Sour taste, react with metals, turn litmus red.
  • Bases: Feel slippery, turn litmus blue.
• Boyle's Limitation: It was more empirical, without theoretical background or predictive power due to lack of knowledge on chemical compositions in the 17th century.

• Acid: Substances that dissociate in water to form hydrogen ions (H+).
• Base: Substances that dissociate in water to form hydroxide ions (OH−).
• Example
  • HCl(aq) → H⁺(aq) + Cl⁻(aq)
  • NaOH(aq) → Na⁺(aq) + OH⁻(aq)
• Limitations
  • Applies only to substances soluble in water.
  • Cannot explain bases like NH₃​ which don’t contain oxygen.

📌 Real World Example

• Lemon Juice is acidic and can turn blue litmus paper red!
• Soap feels slippery due to its basic nature!

• Acid: A proton donor.
• Base: A proton acceptor.
• It’s more expansive, considering a wider range of species as acids and bases, without referring to solvents.
• Example
  • Reaction of NH₃​(g) and HCl(g) leading to formation of NH₄​Cl (s).

🎉 Fun Fact

• Brønsted–Lowry theory does not replace the Arrhenius theory but rather expands upon it!

• Neutralization of Sulfuric Acid and Potassium Hydroxide
  • H_2​SO₄​(aq)+2KOH (aq) → K₂​SO₄​(aq)+2H₂​O(l)
• Ionization of Ammonia in Water
  • NH_{3 ​}(aq) + H₂​O(l) ⇌ NH₄⁺​(aq) + OH⁻(aq)