Review: 1. Write equations to represent how the following ionize in water according to Arrhenius theory? a. Sulfuric acid b. lithium hydroxide 2. Write equations to show the hydrolysis reaction that each Bronsted-Lowry base would undergo when added to water. a. Nitrite ion, NO2-1 b. methylamine, CH3NH2 3. What is the conjugate pair of the nitrite ion? 4. What is the conjugate base produced by adding methylamine to water?

Water is not JUST water … Water and the pH Scale: Water is not JUST water … H2O undergoes a process called auto-ionization Auto-ionization can be explained using Arrhenius OR Bronsted-Lowry The Arrhenius version: The Bronsted-Lowry version:

Water is not JUST water … Water and the pH Scale: Water is not JUST water … This is an extremely reactant-favored equilibrium process! (Like all equilibrium rxn’s, we can write a K expression) The Arrhenius version: H2O(l) ↔ H+(aq) + OH-(aq) The Bronsted-Lowry version: H2O(l) + H2O(l) ↔ H3O+(aq) + OH-(aq)

H2O(l) + H2O(l) ↔ H3O+(aq) + OH-(aq) Kw = [H3O+] [OH-] = 1x10-14 Water and the pH Scale: H2O(l) + H2O(l) ↔ H3O+(aq) + OH-(aq) Kw = [H3O+] [OH-] = 1x10-14 H2O(l) ↔ H+(aq) + OH-(aq) Kw = [H+] [OH-] = 1x10-14 So what??? There is always a mathematical relationship between (H+) H3O+ and OH- ions in solution due to the equilibrium of water [H3O+] = [OH-] neutral solution [H3O+] > [OH-] acidic solution [H3O+] < [OH-] basic solution

Math Check: An aqueous solution has an [H3O+] = 2.3x10-4 M. What is the hydroxide ion concentration and is this solution acidic or alkaline?

Water and the pH Scale: pH – The simple man’s way of determining if a solution is acidic or basic pH = -log [H3O+] or pH = -log [H+]

Water and the pH Scale: pOH values can also be calculated the same way … pOH = -log [OH-] pOH gives the same information as pH, just in reverse

Water and the pH Scale: One more useful formula … pOH + pH = 14

Practice: Try 1, 3, 5, 6, and 9. (The answers are on back and complete answer key is posted, make sure you can do these!!!)