CHM152 NAU - Acids and Bases

Acids

• Produces hydrogen ions (H+) in aqueous solutions

• React with active metals

• Corrosive

• Reacts with carbonates, producing CO₂

• Reacts with bases to form ionic salts

Common Acids

HNO_3, HSO₃, HCl, H₃PO₄, HC₂H₃O₂, HF, H₂CO₃, H₃BO₃

Binary Acids

• Have acidic hydrogen attached to a nonmetal atom

  • HCl, HF, HBr, HI, etc.

Oxyacids

• Have acid hydrogens attached to an oxygen atom

  • H₂SO₄, HNO₃

Carboxylic Acids

• Have a -COOH group

  • HC₂H₃O₂, H₃C₆H₅O₇

• Only the first H in the formula is acidic (the H on the -COOH)

Bases

• Accepts protons (H⁺)

• Release hydroxide ions (OH^-) in aqueous solution

• Reacts with acids to form ionic salts

  • Does this by neutralizing the acid

Most ionic bases contain ___ ions, but some contain ___ ions.

OH^-, CO₃^2-

Molecular Bases

A base composed of covalently bonded non-metal atoms that typically posses a lone pair of electrons

• e.g., NH₄ (Ammonium)

Covalent Bond

Between non-metals

Ionic Bond

Between a non-metal and metal

Arrhenius Theory

• Bases dissociate in water to produce OH^- ions and cations

• Acids ionize in water to produce H⁺ ions and anions

H⁺ ions are ____.

Protons

Arrhenius Acid-Base Reaction

Acid + Base —> Salt + Water

Brønsted-Lowry Theory

• The acid is an H⁺ donor

• The base is an H⁺ acceptor

Brønsted-Lowry Acid-Base Reaction

H-A + :B ←→ :A^- + H-B⁺

Amphoteric

Substances that can act as either an acid or base

Conjugate acid-base pairs are two substances related to each other by…

A transfer of a single proton

Lewis Definition

• A Lewis acid is an electron pair acceptor

• A Lewis base is an electron pair donor

Why does the Lewis definition of an acid allow substances without H to be classified as acids?

A Lewis acid has an empty orbital (or can arrange electrons to create an empty orbital) that can accept an electron pair

• E.g., BF₃ + :NH₃ → F₃B:NH₃

Cationic Lewis Acids

Small, highly charged, metal ions that have lost their electrons, and can therefore act as Lewis acids