APCHEM - UNIT 8: Acids and Bases

• Acids: Substances that can donate protons (H+) and typically have a sour taste.

• Bases: Substances that can accept protons or donate hydroxide ions (OH-) and usually feel slippery.

8.1 Intro to Acids and Bases

Essential Knowledge Statements:

• The concentrations of hydronium ion and hydroxide ion are often reported as pH and pOH, respectively

  • EQN: pH = -log[H₃O+]

  • EQN: pOH = -log[OH-]

• The terms “hydrogen ion and “hydronium ion” and the symbols H+ (aq) and H₃O+ (aq) are often used interchangeably for the aqueous ion of hydrogen

• Water autoionizes with an equilibrium constant Hw

  • EQN: K_w = [H₃O+][OH-] = 1.0×10^-14 at 25 degrees

• In pure water, pH = pOH is called a neutral solution. At 25 degrees, pK_w = 14.0 and thus pH = pOH = 7.0

  • EQN: pK_w = 14 = pH + pOH at 25 degrees

• The value of K_w is temperature dependent, so the pH of pure, neutral water will deviate from 7.0 at temperatures other than 25 degrees