1. The definitions of acids and bases have changed over time. Arrhenius Definition of Acids and Bases: An acid is any substance that adds hydrogen ion (H+) to solution. A base is any substance that adds hydroxide ion (OH-) to solution. Because acids and bases add ions to water, they are both electrolytes and will conduct electricity. Important: Not all compounds that have OH in them are bases For example: CH 3 COOH is acetic acid (vinegar) IV-18: “Pass the Proton” Acid – Base Theories Notes

2. The pH of a solution is determined by: The molarity of the solution AND The identity of the solution (acid, base or neutral) What does pH measure? IV-19: “pHooey!” [H + ] and pH Notes

3. Acids tend to dissociate into H+ ions in solution. Example: HCl (aq)  H + + Cl – IV-19: “pHooey!” [H + ] and pH Notes

4. Bases tend to dissociate into OH- ions in solution. Example: NaOH (aq)  Na + + OH – IV-19: “pHooey!” [H + ] and pH Notes

5. You can think about pH as the “power of hydrogen.” pH measures the concentration of H+ ions in the solution, [H+] pH = [H+] IV-19: “pHooey!” [H + ] and pH Notes

6. pOH is the concentration of OH- ions in solution. pOH = [OH-] IV-19: “pHooey!” [H + ] and pH Notes

7. The pH of water is 7. Water is considered neutral because the number of H+ is equal to the number of OH-. [H+] = [OH-] IV-19: “pHooey!” [H + ] and pH Notes

8. pH + pOH = 14 Water is neutral. Neutral: [H+] = [OH-] The pH of water is 7, therefore the pOH must be 7 as well. pH plus pOH adds to 14. IV-19: “pHooey!” [H + ] and pH Notes

9. pH & pOH scale  log scale Each unit of change in pH represents a tenfold difference in H+ concentration EX: A solution with a pH of 3 has an [H+] ten times greater than a solution with a pH of 4 pH = -log [H+] **Same goes for pOH** pOH = -log [OH-]

11. The pH number of a solution tells you the concentration of H+ ions in solution. A pH of 1 corresponds to a H+ concentration of 0.1 moles/L. [pH of 1= 0.1 M H+] Solutions that are more acidic have more H+ ions. Solutions that are more basic have less H+ ions. IV-19: “pHooey!” [H + ] and pH Notes

12. If you know the pH of a solution, what else do you know? IV-19: “pHooey!” [H + ] and pH Check-In