Created by C. Ippolito July 2007 Acids Bases Salts 19.1 Acid Base Theories 19.2 Hydrogen Ions and Acidity 19.3 Strengths of Acids and Bases 19.4 Neutralization Reactions 19.5 Salts in Solution Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Acid-Base Theories Objectives Define the properties of acids and bases Compare and contrast acids and bases as defined by the theories of Arrhenius, Brønsted-Lowry, and Lewis Created by C. Ippolito July 2007 Updated 12/8/2018

Properties of Acids and Bases taste sour burn indicator color litmus – red btb – yellow methyl orange – red phenolphthalein - clear electrolyte in solution Bases taste bitter slippery indicator color litmus – blue btb – blue methyl orange – orange phenolphthalein - pink electrolyte in solution Created by C. Ippolito July 2007 Updated 12/8/2018

Arrhenius Acids and Bases hydrogen containing compounds release H+ ions in aqueous solutions HCl, HNO3, H2SO4, H3PO4, H2CO3 Monoprotic Acid (HCl, HNO3) release one H+ ion Diprotic Acid (H2SO4, H2CO3) releases two H+ ion Triprotic Acid (H2CO3) Bases release OH- ions in aqueous solutions KOH, NaOH, Ca(OH)2, Mg(OH)2 Created by C. Ippolito July 2007 Updated 12/8/2018

Brønsted-Lowry Acids and Bases hydrogen-ion donors Base hydrogen-ion acceptor explains ammonia as a base NH3(aq) + H2O(ℓ)  NH4+(aq) + OH-(aq) Conjugate Acid particle formed when a base gains a hydrogen ion - NH4+(aq) Conjugate Base particle formed when an acid donate a hydrogen ion - OH-(aq) Amphoteric Substance can act as both and acid or base NH3(aq) + H2O(ℓ)  NH4+(aq) + OH-(aq) (water – acid) HCl(aq) + H2O(ℓ)  H3O+(aq) + Cl-(aq) (water – base) Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Lewis Acids and Bases Acids accepts a pair of electrons during a reaction Bases donates a pair of electrons during a reaction Created by C. Ippolito July 2007 Updated 12/8/2018

Hydrogen Ions and Acidity Objectives Define strong acids and weak acids Describe how [H+] and [OH-] are related in an aqueous solution Classify a solution as neutral, acidic, or basic given the hydrogen-ion or hydroxide-ion concentration Convert hydrogen-ion concentrations into pH values and hydroxide-ion concentrations into pOH values Describe the purpose of an acid-base indicator Created by C. Ippolito July 2007 Updated 12/8/2018

Hydrogen Ions from Water Self-Ionization water molecules react to form ions H2O(ℓ) + H2O(ℓ)  H3O H2O(ℓ) ) + OH-(aq) Neutral Solution in pure water at 25°C [H+(aq)] = [OH-(aq)] only 1 x 10-7 M each Created by C. Ippolito July 2007 Updated 12/8/2018

Ion Product Constant for Water (Kw) Kw = [H+] x [OH-] = 1.0 x 10-14 Acidic Solution [H+] is greater than [OH-] [H+] is greater than 1 x 10-7 Basic Solution a.k.a. alkaline solution [H+] is less than [OH-] [H+] is less than 1 x 10-7 Created by C. Ippolito July 2007 Updated 12/8/2018

Finding the [OH-] of a Solution Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 The pH Concept pH scale range from 0 to 14 Acid Solution – pH<7 [H+] > 1 x 10-7 M Neutral Solution – pH=7 [H+] = 1 x 10-7 M Basic Solution – pH>7 [H+] < 1 x 10-7 M Calculating pH pH = -log[H+] Neutral Solution [H+] = 1 x 10-7 pH = -log(1 x 10-7) = -(log 1 + log 10-7) pH = -(0.0 + (-7.0)) = 7 Calculating pOH pOH = -log[OH-] Created by C. Ippolito July 2007 Updated 12/8/2018

Relationship among [H+], [OH-], and pH Created by C. Ippolito July 2007 Updated 12/8/2018

Calculating pH from [H+] Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Using pH to Find [H+] Created by C. Ippolito July 2007 Updated 12/8/2018

Calculating pH from [OH-] Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Measuring pH Acid-Base Indicators change colors in acid/base solutions Created by C. Ippolito July 2007 Updated 12/8/2018

Strengths of Acids and Bases Objectives Define strong acids and weak acids Describe how an acid’s strength is related to the value of its acid dissociation constant Calculate an acid dissociation constant (Ka) from concentration and pOH measurements Order acids by strength according to their acid dissociation constants (Ka) Order bases by strength according to their base dissociation constants (Kb) Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Strong and Weak Acids Strong Acids ionize completely in solution Weak Acids ionize slightly in solution Acid Dissociation Constant (Ka) the stronger the acid the larger the Ka value Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Strong and Weak Bases Strong Bases ionize completely in solution Weak Bases ionize slightly in solution Base Dissociation Constant (Kb) the stronger the base the larger the Kb value Created by C. Ippolito July 2007 Updated 12/8/2018

Calculating Dissociation Constants To find the Ka of a weak acid or the Kb of a weak base, substitute the measured concentrations of all substances at equilibrium into the Ka or Kb expression Created by C. Ippolito July 2007 Updated 12/8/2018

Calculating a Dissociation Constant Created by C. Ippolito July 2007 Updated 12/8/2018

Neutralization Reactions Objectives Define the products of an acid-base reaction Explain how acid-base titration is used to calculate the concentration of an acid or a base Explain the concept of equivalence in neutralization reactions Describe the relationship between equivalence point and the end of a titration Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Acid-Base Reactions Neutralization Reactions acids and bases react in an aqueous solution to form a salt and water HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) 1 mole acid : 1 mole base H2SO4(aq) +2NaOH(aq)  Na2SO4(aq) + 2H2O(l) 1 mole acid : 2 mole base 2HCl(aq) + Ca(OH)2(aq)  CaCl2(aq) + 2H2O(l) 2 mole acid : 1 mole base Equivalence Point when the number of moles of hydrogen ions equals the number of moles of hydroxide ions Created by C. Ippolito July 2007 Updated 12/8/2018

Finding the Number of Moles of an Acid in Neutralization Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Titration process of adding a known amount of known concentration to determine the concentration of another solution Standard Solution solution of known concentration End Point point where indicator changes color showing neutralization has occurred Created by C. Ippolito July 2007 Updated 12/8/2018

Determining the Concentration of an Acid by Titration Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Salts in Solution Objectives Describe when a solution of a salt is acidic or basic Demonstrate with equations how buffers resist changes in pH Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Salt Hydrolysis cations or anions of dissociated salt remove hydrogen ions from or donate hydrogen ions to water Salts formed by weak acid and strong base accept hydrogen ion to form BASIC SOLUTIONS CH3COONa(aq) CH3OO-(aq) + Na+(aq) CH3OO-(aq) + H2O(l)  CH3COOH(aq) + OH-(aq) formed by strong acid and weak base donate hydrogen to form ACIDIC SOLUTIONS NH4Cl(aq) NH4+(aq) + Cl-(aq) NH4+(aq) + H2O(l)  NH3 (aq) + H3O+(l) Created by C. Ippolito July 2007 Updated 12/8/2018

Created by C. Ippolito July 2007 Buffers Buffer solution in which the pH remains relatively constant with the addition of small amounts of acid or base solution of weak acid and its salt or solution of weak base and its salt Buffer Capacity amount of acid or base that can be added to buffer before a significant pH change occurs Created by C. Ippolito July 2007 Updated 12/8/2018