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Chapter 19Chapter 19
Acids and BasesAcids and Bases
TEKSTEKS
(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 Properties of Acids and BasesBases
AcidsAcids Tastes sourTastes sour reacts with metals to reacts with metals to
produce hydrogen gasproduce hydrogen gas Reacts with carbonates Reacts with carbonates
to produce carbon to produce carbon dioxidedioxide
conducts electricity so conducts electricity so are good electrolytesare good electrolytes
Turns blue litmus redTurns blue litmus red Has a pH between 0-6Has a pH between 0-6 Reacts with a base to Reacts with a base to
produce salt and produce salt and waterwater
BasesBases Tastes bitterTastes bitter SlipperySlippery conducts electricityconducts electricity Turns red litmus Turns red litmus
blueblue Reacts with an acid Reacts with an acid
to produce salt and to produce salt and waterwater
Has a pH above 7Has a pH above 7
Ions in SolutionIons in SolutionAcidic 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-Arrhenius vs Bronstead-LowryLowry
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 SubstancesAmphoteric Substances
Amphoteric-Amphoteric- a substance that a substance that can act as both acids and basescan act as both acids and bases– Ex: WaterEx: Water
When HF dissolves in water, When HF dissolves in water, water acts as basewater acts as base
When NHWhen NH33 dissolves in water, dissolves in water, water acts as acid water acts as acid
Strong Acids vs Weak AcidsStrong Acids vs Weak Acids
–http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s1/index.htm
19.2 Strengths of Acids19.2 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 electrolytesEx: HCl, HNO3, H2SO4
Poor conductors of electricity
Reactions shown with
Reactions shown with >
Strong Base vs Weak BaseStrong Base vs Weak Base
–http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s2/index.htm
19.2 Strengths of Bases19.2 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?19.3 What is pH?
Pure water contains equal Pure water contains equal numbers of Hnumbers of H++ and OH and OH-- ions ions
KKww = [H = [H++] [OH] [OH--]]
Use 1.0x10Use 1.0x10-14-14 M M for Kfor Kww
Ion Product Constant of Ion Product Constant of WaterWater
Ion Product Constant of Ion Product Constant of Water-Water- K Kww- the value of the - the value of the equilibrium constant for equilibrium constant for waterwater
At 298 K, KAt 298 K, Kw w is 1.0 x 10is 1.0 x 10-14-14
KKww = [H = [H++] [OH] [OH--]]
pHpH
pHpH- the negative logarithm of - the negative logarithm of the hydrogen ion the hydrogen ion concentrationconcentration
pH = -log [HpH = -log [H++] ]
Math CalculationsMath Calculations
pH + pOH = 14pH + pOH = 14 pH= -log(HpH= -log(H++)) pH when given pOH = 14- (-log OH)pH when given pOH = 14- (-log OH)
pH ScalepH Scale
pH below 7 is an acidpH below 7 is an acidpH above 7 is a basepH above 7 is a basepH = 7 is neutralpH = 7 is neutral
pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
pH ScalepH Scale
http://www.purchon.com/chemistry/http://www.purchon.com/chemistry/flash/ph.swfflash/ph.swf
19.4 Neutralization19.4 Neutralization
Neutralization Reaction-Neutralization Reaction- acid acid & base react to produce a salt & base react to produce a salt & water& water– a Double-Replacement a Double-Replacement
ReactionReactionSalt-Salt- an ionic compound an ionic compound
formed from the cation of a formed from the cation of a base & anion of an acidbase & anion of an acid
Acid-Base Indicator-Acid-Base Indicator- a a compound that changes color compound that changes color as it is placed in either an as it is placed in either an acid or baseacid or base
TitrationTitration
The process in which an acid-base The process in which an acid-base neutralization reaction is used to neutralization reaction is used to determine the concentration of a determine the concentration of a solution of unknown concentration.solution of unknown concentration.
End PointEnd Point
The point at which an indicator used The point at which an indicator used in a titration changes colorin a titration changes color
BuffersBuffers
A solution that resists changes in pH A solution that resists changes in pH when limited amounts of acids and when limited amounts of acids and bases are added.bases are added.