Chapter 19 Acids and Bases

TEKS (G) define acids and bases and distinguish between Arrhenius and Bronsted-Lowry definitions and predict products in acid base reactions that form water; (H) understand and differentiate among acid-base reactions, precipitation reactions, and oxidation-reduction reactions; (I) define pH and use the hydrogen or hydroxide ion concentrations to calculate the pH of a solution; and

Properties of Acids and Bases Tastes sour reacts with metals to produce hydrogen gas Reacts with carbonates to produce carbon dioxide conducts electricity so are good electrolytes Turns blue litmus red Has a pH between 0-6 Reacts with a base to produce salt and water Tastes bitter Slippery conducts electricity Turns red litmus blue Reacts with an acid to produce salt and water Has a pH above 7

Ions in Solution contains more H+ ions than OH- ions H+ > OH- Acidic Solution Neutral solutions Basic Solution contains more H+ ions than OH- ions H+ > OH- neither acidic or basic equal # of H+ and OH- ions H+ = OH- contains more OH- ions than H+ ions H+ < OH-

Arrhenius vs Bronstead-Lowry an acid is a substance that ionizes to produce hydrogen ions in aqueous solution States that an acid is a hydrogen-ion donor a base dissociates to produce a hydroxide ion in aqueous solution a base is a hydrogen-ion acceptor

Amphoteric Substances Amphoteric- a substance that can act as both acids and bases Ex: Water When HF dissolves in water, water acts as base When NH3 dissolves in water, water acts as acid

Strong Acids vs Weak Acids http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s1/index.htm

19.2 Strengths of Acids Strong Acids Weak Acids acid that ionizes completely acid that ionizes only partially in dilute aqueous solutions Ex: HC2H3O2, H2CO3 Good conductors of electricity, makes great electrolytes Ex: HCl, HNO3, H2SO4 Poor conductors of electricity Reactions shown with  Reactions shown with >

Strong Base vs Weak Base http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s2/index.htm

19.2 Strengths of Bases Strong Base Weak Base dissociate completely into metal ions and hydroxide ions Ex: NaOH, Ca(OH)2 ionizes only partially in dilute aqueous solutions to form conjugate acid of the base and hydroxide ion Ex: CH3NH2

19.3 What is pH? Pure water contains equal numbers of H+ and OH- ions Kw = [H+] [OH-] Use 1.0x10-14 M for Kw

Ion Product Constant of Water Ion Product Constant of Water- Kw- the value of the equilibrium constant for water At 298 K, Kw is 1.0 x 10-14 Kw = [H+] [OH-]

pH pH- the negative logarithm of the hydrogen ion concentration pH = -log [H+]

Math Calculations pH + pOH = 14 pH= -log(H+) pH when given pOH = 14- (-log OH)

pH Scale pH below 7 is an acid pH above 7 is a base pH = 7 is neutral

pH of Common Substances Timberlake, Chemistry 7th Edition, page 335

pH Scale http://www.purchon.com/chemistry/flash/ph.swf

19.4 Neutralization Neutralization Reaction- acid & base react to produce a salt & water a Double-Replacement Reaction Salt- an ionic compound formed from the cation of a base & anion of an acid

Acid-Base Indicator- a compound that changes color as it is placed in either an acid or base

Titration The process in which an acid-base neutralization reaction is used to determine the concentration of a solution of unknown concentration.

End Point The point at which an indicator used in a titration changes color

Buffers A solution that resists changes in pH when limited amounts of acids and bases are added.