definition - increases the concentration of H+ ions when dissolved in water 

• the H+ ion generally forms H3O+ w/ water
• Bronsted-Lowry definition - donates proton to another substance
  • even applies to substances not dissolved in water
  • weak H-X bond, stable base, positively polarized H >> stronger acid
• Lewis definition - electron-pair acceptor
• pH = -log [H+]
• strong acid - complete dissociates, [H+] = [acid]
  • HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
• weak acid - partially dissociates
  • Ka = [H+][conjugate base] / [acid]
  • [H+] = [conjugate base] when Ka is very small
• polyprotic acids - have more than 1 ionizable H atom
  • easier to remove 1st proton than second
  • Ka becomes smaller
• binary acids - contains hydrogen and 1 other element
  • bond strength determines acid strength
  • element increases in size >> bond strength decreases >> acid strength increases
  • element electronegativity increases >> polarity increases >> acid strength increases
• oxyacids - OH and oxygen bonded to a central atom
  • element electronegativity increases, # of oxygen increases >> acid strength increases
• carboxylic acids - contains a carboxyl group, largest cateogry of organic acids
  • # of electronegative atoms increase >> acid strength increases

Find the pH of a 0.001 M solution of acetic acid  

• Ka = 1.8 x 10-5
• Ka = [H+] [acetate] / [acetic acid] = x2 / 0.001
• x = [(1.8 x 10-5) (0.001)]1/2 = 1.3 x 10-4 = [H+]
• pH = -log [H+] = 3.87

Find the pH of 0.1 M solution of HCl  

• strong acid, completely dissociates
• pH = -log [HCl] = 1