Acids & BasesAcids & Bases

Naming ReviewNaming Review

Binary Acids1. Start the acid name with “hydro-“2. Add the root of the second element with the suffix “ic”3. Add the word “acid” EX. HCl- hydrochloric acid

Polyatomic Acids• Use the root name of the polyatomic• Add “ic” if the polyatomic ends in –ate What I ATE was ICky• Add “ous” if the polyatomic ends in –ite I took a bITE it was deliciOUS• Add the word “acid”

DefinitionsDefinitions

AcidsAcids• Ionize to form hydronium ions (H3O+) in water

(Arrhenius)• Proton donor (Bronsted-Lowry)• Electron-pair acceptor (Lewis)

HCl + H2O H3O+ + Cl–

DefinitionsDefinitions

BasesBases• Dissociate or ionize to form hydroxide ions (OH-) in water (Arrhenius)• Proton acceptor (Bronsted - Lowry)• Electron-pair donor (Lewis)

NH3 + H2O NH4+ + OH-

Acid-Base ReactionsAcid-Base Reactions

Conjugate Base – the species that remains Conjugate Base – the species that remains after the acid has given up a protonafter the acid has given up a proton

Conjugate Acid – the species that is formed when the base gains a proton

HCl + H2O H3O+ + Cl-acid conjugate

baseconjugate acid

base

HF + H2O F- + H3O+

Acid

Base

Conjugate Acid

Conjugate Base

HF

H2O

H3O+

F-

Acid-Base ReactionsAcid-Base Reactions

PropertiesProperties

sour taste

corrosive

electrolytes

turn litmus red

react with metals to form H2 gas

bitter taste

corrosive

electrolytes

turn litmus blue

slippery feel

UsesUses

H3PO4 - soft drinks, fertilizer, detergents

H2SO4 - fertilizer, car batteries

HCl - gastric juice

HC2H3O2 - vinegar

UsesUses

NaOH - lye, drain and oven cleaner

Mg(OH)2 - laxative, antacid

NH3 - cleaners, fertilizer

Strong vs. WeakStrong vs. Weak

Strong Acid/BaseStrong Acid/Base• 100% ions in water – completely dissociate• strong electrolyte

Weak Acid/BaseWeak Acid/Base• few ions in water –

incomplete dissociation• weak electrolyte

- +

- +

Strong AcidsStrong Acids

H2SO4 Sulfuric Acid

HClO4 Perchloric Acid

HCl Hyrochloric AcidHNO3 Nitric Acid

HBr Hydrobromic AcidHI Hydroidic Acid

Strong BasesStrong Bases

Ca(OH)2 Calcium hydroxide

Sr(OH)2 Strontium hydroxide

Ba(OH)2 Barium hydroxide

NaOH Sodium hydroxideKOH Potassium hydroxideRbOH Rubidium hydroxideCsOH Cesium hydroxide

pH ScalepH Scale

0

7INCREASING

ACIDITY NEUTRALINCREASING

BASICITY

14

pHpH• a measure of the concentration of

H3O+ ions in solution• measured with a pH meter or an

indicator with a wide color range

pH ScalepH Scale

pH of Common SubstancespH of Common SubstancespH of Common SubstancespH of Common Substances

Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA?

ConcepTestConcepTest

A B

ACID + BASE ACID + BASE SALT + WATER SALT + WATER

HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO

Neutralization does not always mean pH = 7.

=

Neutralization ReactionNeutralization Reaction

KOH + HNO3 H2O + KNO3

Acid?

Base?

Salt?

HNO3

KOH

KNO3

Neutralization ReactionNeutralization Reaction

IndicatorsIndicators

IndicatorIndicator• Substance that changes color in an acid or base• Acid-base indicators are very weak acids and bases that change

color when they:– accept a proton from acid – donate one to a base

Indicator Color of acid Color of base

Litmus paper Red Blue

Phenolphthalein Colorless Pink

Goldenrod Yellow Red

Bromothymol blue Yellow Blue

TitrationTitration

The controlled addition and measurement of the amount of a solution of known concentration required to react completely with a measured amount of solution of unknown concentration

Equivalence Point – the point at which two solutions used in a titration are present in chemically equivalent amounts• Occurs at a pH that is halfway between the two curves

End Point – the point at which an indicator changes color

TitrationTitration

Beaker – vinegar + phenolphthaleinBuret – sodium hydroxide

As soon the liquid in the beaker

changes color, stop the dropping. Notice the amount

of titrating solution used

Titration CurvesTitration Curves

Titration CurvesTitration Curves

strong acid / strong base weak acid / strong base

H2O: Acid or Base?H2O: Acid or Base?

Amphoteric – a species that can react as either an acid or a base

NH3 + H2O NH4+ + OH-

HCl + H2O H3O+ + Cl– acid base

base acid

Self-Ionization of H2OSelf-Ionization of H2O

Two water molecules produce a hydronium ion and a hydroxide ion by transfer of a proton

H2O + H2O <----> H3O + OH⁺ ⁻ At 25 C – the concentrations of H3O + OH in pure water are 1.0x10⁺ ⁻ -7M [ H3O ] = 1.0x10⁺ -7M [ OH ] = 1.0x10⁻ -7M Ionization constant of water is Kw

Kw = [ H3O ] [ OH ]⁺ ⁻

Kw = [ H3O ] [ OH ] = (1.0x10⁺ ⁻ -7M)(1.0x10-7M) = 1.0x10-14M2

Ionization ProblemsIonization Problems

A 1x10-4M solution of HNO3 has been prepared for a lab experiment.

a. Calculate [ H3O ] ⁺

b. Calculate [ OH ]⁻

pH & ConcentrationpH & Concentration

pH of a solution is the negative of the common logarithm of the hydronium ion concentration

pH = -log [ H3O ] ⁺

neutral solution at 25C [ H3O ] = 1.0x10⁺ -7MpH = -log (1.0x10-7) = -(-7) = 7

pOH = -log (1.0x10-7) = -(-7) = 7

pH + pOH = 14

Kw= [ H3O ] [ OH ] =1.0x10⁺ ⁻ -14M2

-log(1.0x10-14) = 14

pH & Conc. CalculationspH & Conc. Calculations

1. What is the pH of a 1x10-3M NaOH solution?

2. What is the pH of a solution if the [ H3O ] ⁺is 3.4x10-5M?

3. Determine the hydronium ion of an aqueous solution that has a pH of 4.0

pH & Conc. CalculationspH & Conc. Calculations

4. The pH of a solution is measured and determined to be 7.52

a. What is the hydronium ion concentration?

b. What is the hydroxide ion concentration?

c. Is the solution acidic or basic?