Chapter 9 Acids and Bases Ionization of Water The pH Scale LecturePLUS Timberlake

LecturePLUS Timberlake Ionization of Water Occasionally, in water, a H+ is transferred between H2O molecules . . . . . . . . H:O: + :O:H H:O:H + + :O:H- . . . . . . . . H H H water molecules hydronium hydroxide ion (+) ion (-) LecturePLUS Timberlake

LecturePLUS Timberlake Pure Water is Neutral Pure water contains small, but equal amounts of ions: H3O+ and OH- H2O + H2O H3O+ + OH- hydronium hydroxide ion ion 1 x 10-7 M 1 x 10-7 M H3O+ OH- LecturePLUS Timberlake

LecturePLUS Timberlake Ion Product of Water Kw [ ] = Molar concentration Kw = [ H3O+ ] [ OH- ] = [ 1 x 10-7 ][ 1 x 10-7 ] = 1 x 10-14 LecturePLUS Timberlake

LecturePLUS Timberlake Acids Increase H+ HCl (g) + H2O (l) H3O+ (aq) + Cl- (aq) More [H3O+] than water > 1 x 10-7M As H3O+ increases, OH- decreases [H3O+] > [OH-] H3O+ OH- LecturePLUS Timberlake

LecturePLUS Timberlake Bases Increase the hydroxide ions (OH-) H2O NaOH (s) Na+(aq) + OH- (aq) More [OH-] than water, [OH-] > 1 x 10-7M When OH- increases, H3O+ decreases [OH] > [H3O+] OH- H3O+ LecturePLUS Timberlake

LecturePLUS Timberlake Using Kw The [OH- ] of a solution is 1.0 x 10- 3 M. What is the [H3O+]? Kw = [H3O+ ] [OH- ] = 1.0 x 10-14 [H3O+] = 1.0 x 10-14 [OH-] [H3O+] = 1.0 x 10-14 = 1.0 x 10-11 M 1.0 x 10- 3 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH1 The [H3O+] of lemon juice is 1.0 x 10-3 M. What is the [OH-] of the solution? 1) 1.0 x 103 M 2) 1.0 x 10-11 M 3) 1.0 x 1011 M LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH1 The [H3O+] of lemon juice is 1.0 x 10- 3 M. What is the [OH-]? [OH- ] = 1.0 x 10 -14 = 1.0 x 10-11 M 1.0 x 10 - 3 LecturePLUS Timberlake

LecturePLUS Timberlake Using the Calculator 1.0 x 10 -14 4.0 x 10-5 Enter 1.0 EE +/- 14  4.0 EE +/- 5 = 2.5 x 10 -10 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH2 The [OH-] of a solution is 5 x 10 -5 M. What is the [H3O+ ] of the solution? 1) 2 x 10- 5 M 2) 1 x 1010 M 3) 2 x 10-10 M LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH2 The [OH-] of a water solution is 5 x 10-5 M. What is the [H3O+] in the solution? [ H3O+] = 1.0 x 10 -14 5 x 10- 5 On some calculators: 1.0 EE +/- 14  5 EE +/- 5 = 2 x 10 -10 M LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH3 A.The [OH-] when [H3O+ ] of 1 x 10- 4 M 1) 1 x 10-6 M 2) 1 x 10-8 M 3) 1 x 10-10 M B.The [H3O+] when [OH- ] of 5 x 10-9 M 1) 1 x 10- 6 M 2) 2 x 10- 6 M 3) 2 x 10-7 M LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH3 Kw = [H3O+ ][OH-] = 1.0 x 10 14 A. (3) [OH- ] = 1.0 x 10 -14 = 1.0 x 10 -10 1.0 x 10- 4 B. (2) [H3O+] = 1.0 x 10 -14 = 2 x 10 - 6 5 x 10- 9 LecturePLUS Timberlake

LecturePLUS Timberlake pH Indicates the acidity [H3O+] of the solution pH = - log [H3O+] From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen) LecturePLUS Timberlake

pH A strong acid A strong base SOURCE: http://en.wikipedia.org/wiki/Image:PH_scale.png#file pH 10-2 10-3 10-5 10-4 10-8 10-7 10-6 [H+] M 10-10 10-9 10-11 10-12 10-13 10-14 10-1 100 A strong acid A strong base Most living cells have a very narrow range of tolerance for pH, i.e. [H+]. The [H+] concentration will be important (either explicitly or implicitly) for many other topics in biology. [H+] is controlled in all biological organisms, and in virtually all biochemical experiments. Each pH unit represents a factor of 10 difference in [H+]. The pH scale goes from 0 to 14—because [H+][OH-] = 10-14

LecturePLUS Timberlake pH In the expression for [H3O+] 1 x 10-exponent the exponent = pH [H3O+] = 1 x 10-pH M LecturePLUS Timberlake

LecturePLUS Timberlake pH Range 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] Acidic Basic LecturePLUS Timberlake

LecturePLUS Timberlake Some [H3O+] and pH [H3O+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11 M 11 LecturePLUS Timberlake

LecturePLUS Timberlake pH of Some Common Acids gastric juice 1.0 lemon juice 2.3 vinegar 2.8 orange juice 3.5 coffee 5.0 milk 6.6 LecturePLUS Timberlake

LecturePLUS Timberlake pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4 milk of magnesia 10.6 household ammonia 11.0 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH4 A. The [H3O+] of tomato juice is 1 x 10-4 M. What is the pH of the solution? 1) - 4 2) 4 3) 8 B. The [OH-] of an ammonia solution is 1 x 10-3 M. What is the pH of the solution? 1) 3 2) 11 3) -11 LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH4 A. pH = - log [ 1 x 10-4] = -(- 4) = 4 B. [H3O+] = 1 x 10-11 pH = - log [ 1 x 10- 11] = -(- 11) = 11 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH5 The pH of a soap is 10. What is the [H3O+] of the soap solution? 1) 1 x 10 - 4 M 2) 1 x 1010 M 3) 1 x 10 - 10 M LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH5 The pH of a soap is 10. What is the [H3O+] of the soap solution? [H3O+] = 1 x 10-pH M = 1 x 10-10 M LecturePLUS Timberlake

LecturePLUS Timberlake pH on the Calculator [H3O+] is 4.5 x 10-6 M pH = 4.5 x EXP(or EE) 6+/- LOG +/- = 5.35 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH6 A soap solution has a [H3O+] = 2 x 10-8 M. What is the pH of the solution? 1) 8 2) 7.7 3) 6 LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH6 A soap solution has a [H3O+] = 2.0 x 10-8 M. What is the pH of the solution? B) 2.0 EE 8 +/- LOG +/- = 7.7 LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check pH7 Identify each solution as 1. acidic 2. basic 3. neutral A. _____ HCl with a pH = 1.5 B. _____ Pancreatic fluid [H+] = 1 x 10-8 M C. _____ Sprite soft drink pH = 3.0 D. _____ pH = 7.0 E. _____ [OH- ] = 3 x 10-10 M F. _____ [H+ ] = 5 x 10-12 LecturePLUS Timberlake

LecturePLUS Timberlake Solution pH7 Identify each solution as 1. acidic 2. basic 3. neutral A. _1__ HCl with a pH = 1.5 B. _2__ Pancreatic fluid [H+] = 1 x 10-8 M C. _1__ Sprite soft drink pH = 3.0 D. _3__ pH = 7.0 E. _1__ [OH-] = 3 x 10-10 M F. _2__ [H+] = 5 x 10-12 LecturePLUS Timberlake

LecturePLUS Timberlake Acid Rain Unpolluted rain has a pH of 5.6 Rain with a pH below 5.6 is “acid rain“ CO2 in the air forms carbonic acid CO2 + H2O H2CO3 Adds to H+ of rain H2CO3 H+ (aq) + HCO3-(aq) Formation of acid rain: 1. Emission of sulfur and nitrogen oxides from the burning of fuels expecially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N2 SO2 26 million tons in 1980 NO and NO2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO2 2. Reactions in the atmosphere form SO3 2SO2 + O2  2 SO3 3. Reactions with atmosphere water form acids SO3 + H2O  H2SO4 sulfuric acid NO + H2O  HNO2 nitrous acid HNO2 + H2O  HNO3 nitric acid 4. Effects of Acid Rain Decline in fish populations in rivers and lasts due to toxic effect of Al leached from soil by acid rain Extensive fish kills in spring from runoff due to accumulation of large amounts of acid on the snow Dissolves minerals Mg, Ca, and K from the soil and waxy coatings that protect leaves from bacteria Corrodes metals, textiles, paper and leather LecturePLUS Timberlake

LecturePLUS Timberlake Sources of Acid Rain Power stations Oil refineries Coal with high S content Car and truck emissions Bacterial decomposition, and lighting hitting N2 LecturePLUS Timberlake

LecturePLUS Timberlake SO2 26 million tons in 1980 NO and NO2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO2 Reactions with oxygen in air form SO3 2SO2 + O2 2 SO3 Reactions with water in air form acids SO3 + H2O H2SO4 sulfuric acid NO + H2O HNO2 nitrous acid HNO2 + H2O HNO3 nitric acid LecturePLUS Timberlake

LecturePLUS Timberlake Effects of Acid Rain Leaches Al from soil, which kills fish Fish kills in spring from runoff due to accumulation of large amounts of acid in snow Dissolves waxy coatings that protect leaves from bacteria Corrodes metals, textiles, paper and leather LecturePLUS Timberlake