Chapter 19.1 Acid-Base Theories Chemistry I Mrs. Ragsdale

Properties of Acids Taste sour – typically edible When dissolved in water (placed in solution), they become electrolytes Change the color of an acid-base indicator Score anywhere from 0 – 6.9 on the pH scale

Properties of Bases Taste bitter – typically poisonous Feel slippery Think soap: it feels slick and tastes very bitter Change the color of an acid-base indicator Also form electrolytes when placed in solution Score anywhere from 7.1 – 14 on a pH scale

Common Acids and Bases Acids Bases HCl – Hydrochloric acid HNO₃ - Nitric acid H₂SO₄ - Sulfuric acid H₃PO₄ - Phosphoric acid NH₄ - Ammonium NaOH – Sodium hydroxide KOH – Potassium hydroxide Ca(OH)₂ - Calcium hydroxide Mg(OH)₂ - Magnesium hydroxide NH₃ - Ammonia

Defining Acids and Bases Three main ways to define acids and bases Arrhenius Acids and Bases Bronsted-Lowry Acids and Bases Lewis Acids and Bases

Arrhenius Acids and Bases Acids are hydrogen-containing compounds that ionize to yield hydrogen ions (H⁺) in aqueous solution. Bases are compounds that ionize to yield hydroxide ions (OH⁻) in aqueous solution

Arrhenius Acids Can be monoprotic, diprotic, or triportic acids Mono – HCl Di – H₂SO₄ Tri – H₃PO₄ Release H⁺ ions in solution

Arrhenius Bases Compounds that ionize in solution that yield hydroxide (OH⁻) ions

Bronsted-Lowry Acids and Bases Acids are hydrogen proton (H⁺) donators Bases are hydrogen proton acceptors Important because Arrhenius definition leaves out acids and bases like ammonia and ammonium!

Conjugate Acids and Bases When an acid donates a hydrogen proton on the left side of a reaction, it becomes a base on the right. On the other hand when a base on the left accepts a proton, on the right it becomes an acid because it now has a hydrogen proton it can donate. Therefore we have conjugate acid-base pairs.

Final Tidbits… Hydronium ions (H₃O⁺) can be formed when acids are added to water. Hydronium ions are considered bases. HCl(g) + H₂O (l) ↔ H₃O⁺(aq) + Cl⁻(aq) Water is amphoteric. This means it can act as an acid or a base. It can acts as an acid OH⁻ or as a base as H₃O⁺

Lewis Acids and Bases An acid accepts a pair of electrons during a reaction while a base donates a pair of electrons

Putting it all together!

Acid-Base Definitions Your handy dandy chart! Acid-Base Definitions Type Acid Base Arrhenius H⁺ producer OH⁻ producer Bronsted-Lowry H⁺ donor H⁺ acceptor Lewis Electron-pair acceptor Electron pair donor