Chemistry 14.2

  • Brønsted-Lowry Acids and Bases:

    • Water can act as a Brønsted-Lowry acid by donating protons.

    • Brønsted-Lowry base: Proton acceptor (e.g., ammonia accepts protons from hydrochloric acid).

    • OH5 ion from Arrhenius bases act as Brønsted-Lowry bases.

    • Acid-base reactions involve proton transfer between acid and base.

  • Types of Acids:

    • Monoprotic acids: Donate one proton (e.g., HCl, HNO3).

    • Polyprotic acids: Can donate multiple protons but not all are strong acids.

    • Strong acids ionize completely in solution (e.g., HCl, HNO3).

    • Weak acids release few protons; example: HCN has very low ionization in 1 M solution.

  • Acid Strength:

    • Strong acids: High bond polarity and lower bond energy lead to increased strength.

    • Weak acids, such as acetic acid (CH3COOH), do not ionize completely in water.

  • Brønsted-Lowry Theory Expansion (1923):

    • J. N. Brønsted and T. M. Lowry expanded Arrhenius concepts.

    • Hydrogen chloride (HCl) considered a Brønsted-Lowry acid when reacting with NH3 (ammonia).

  • Bases:

    • Many bases are ionic and dissociate in water (e.g., NaOH).

    • Strong bases completely dissociate and are considered strong electrolytes (e.g., KOH).

    • NH3, despite being a weak electrolyte, produces OH5 ions when dissolved, thus acting as a weak base.

  • Common Aqueous Acids and Bases:

    • Strong Acids: HCl, HNO3, HClO4.

    • Weak Acids: CH3COOH, HF, HCN.

    • Strong Bases: NaOH, KOH.

    • Weak Bases: Ammonia (NH3), various organic nitrogen compounds.