1. 19.2 Hydrogen Ions and Acidity

2. Self-Ionization of Water Water is very polar Water is very polar When the water molecules collide too fast a proton can break off and two ions form When the water molecules collide too fast a proton can break off and two ions form H 2 O → H + + OH - Usually the H + ion reacts with an intact H 2 O molecule to form an hydronium ion H 3 O + Usually the H + ion reacts with an intact H 2 O molecule to form an hydronium ion H 3 O + H + + H 2 O → H 3 O +

3. Algebra Review 10000 = 10 4 ___1___ = 10 -4 ___1___ = 10 -4 10000 10000 Which number is larger 10 4 or 10 6 ? 10 6 Which number is larger 10 -4 or 10 -6 ? 10 -4 think about it what is the larger number 1/10,000 or 1/1,000,000

4. Acidic or basic [H+] > 10 -7 solution is acidic [H+] > 10 -7 solution is acidic [H+] = 10 -7 solution is neutral [H+] = 10 -7 solution is neutral [H+] < 10 -7 solution is basic [H+] < 10 -7 solution is basic Or other way around [OH-] > 10 -7 solution is basic [OH-] > 10 -7 solution is basic [OH-] = 10 -7 solution is neutral [OH-] = 10 -7 solution is neutral [OH-] < 10 -7 solution is acidic [OH-] < 10 -7 solution is acidic

5. H+/OH- concentrations in acids and bases H+ OH- H+ OH- H+ OH- H+ OH- H+ OH- H+ OH- acid neutral base acid neutral base

6. Algebra What’s a logarithm? What’s a logarithm? Writing exponents w/o superscript Writing exponents w/o superscriptExample: log 10 3 = 3 log 10 -3 = -3 -log 10 -3 = 3

7. How much alkalinity/acidity Easier way of expressing acidity/alkalinity Easier way of expressing acidity/alkalinity Focuses only on [H + ] concentration, called pH (little p, big H!!!) Focuses only on [H + ] concentration, called pH (little p, big H!!!) The pH of a solution is the negative logarithm of the hydrogen ion concentration The pH of a solution is the negative logarithm of the hydrogen ion concentration pH = -log [H + ] Artificial scale ranging from 0 to14 Artificial scale ranging from 0 to14

8. Example H2O A few water molecules do this A few water molecules do this H 2 O → H + + OH - Is water an acid or a base? How many molecules break up? How many molecules break up? 10 -7 10 -7 Water has [H + ] = 10 -7 Water has [H + ] = 10 -7 pH = -log 10 -7 pH = -log 10 -7 pH= 7 pH= 7 Because water is considered neutral, pH 7 is the neutral pH Because water is considered neutral, pH 7 is the neutral pH

9. pH of Household Liquids

10. Addtl. definition of an acid/base Acid has a pH < 7 (0 - 6.9) Acid has a pH < 7 (0 - 6.9) Base has a pH > 7 (7.1 - 14) Base has a pH > 7 (7.1 - 14)