CHAPTER 19

Open Textbook to page 586

MANY SUBSTANCES CONTAIN ACIDS.

•VINEGAR (ACETIC ACID)•CARBONATED DRINKS (PHOSPHORIC ACID)•GRAPE JUICE (TARTARIC ACID)•APPLES (MALIC ACID)•LEMONS (CITRIC ACID)

MANY SUBSTANCES CONTAIN BASES.

•LYE (SODIUM HYDROXIDE) FOUND IN COMMERCIAL DRAIN CLEANERS

•MILK OF MAGNESIA (MAGNESIUM HYDROXIDE)

•BAKING SODA (SODIUM BICARBONATE)

ACIDS:

5 GENERAL PROPERTIES:

1)HAVE A SOUR TASTE.

2) CHANGE THE COLOR OF ACID-BASE INDICATORS.

3)REACT WITH ACTIVE METALS TO RELEASE H2 (g).

Mg (s) + 2 HCl (aq) MgCl2 + H2 (g)

4) REACT WITH BASES TO PRODUCE SALTS AND WATER.

5) SOME ACIDS CONDUCT ELECTRIC CURRENT.

ACID NOMENCLATURE

BINARY ACID: ACID THAT CONTAINS ONLY

2 DIFFERENT ELEMENTS,

i.e.,

HYDROGEN AND ONE OF THE MORE ELECTRONEGATIVE ELEMENTS.

NAMES OF BINARY ACIDS

• HF HYDROFLUORIC ACID

• HCl HYDROCHLORIC ACID

• HBr HYDROBROMIC ACID

• HI HYDROIODIC ACID

• H2S HYDROSULFURIC ACID

OXYACIDSACID THAT IS A COMPOUND OF

HYDROGEN,

OXYGEN, AND

a 3rd ELEMENT USUALLY A NONMETAL

COMMON OXYACIDS

• CH3COOH Acetic acid• H2CO3 Carbonic acid• HNO3 Nitric acid• H3PO4 phosphoric acid• H2SO4 sulfuric acid• H2SO3 sulfurous acid• HClO4 perchloric acid• HClO3 chloric acid• HClO2 chlorous acid• HClO hypochlorous acid

Common Industrial Acids

• SULFURIC ACID:MOST COMMONLY PRODUCED INDUSTRIAL CHEMICAL

USED IN CAR BATTERIES

2)NITRIC ACID:

• STAINS PROTEINS YELLOW

• USED IN MAKING EXPLOSIVES

3)PHOSPHORIC ACID:

• USED DIRECTLY FOR MANUFACTURINGFERTILIZERS AND ANIMAL FEED.

• FLAVORING AGENT IN SOFT DRINKS

4)HYDROCHLORIC ACID:

• PRODUCED BY STOMACH

• IN HARDWARE STORES, DILUTE SOL’N KNOWNAS MURIATIC ACID AND IS USED TO CORRECT

ACIDITY OF SWIMMING POOLS AND TO CLEAN MASONRY.

BASES5 GENERAL PROPERTIES

• TASTE BITTER.

• CHANGE THE COLOR OF ACID-BASE INDICATORS.

• DILUTE AQUEOUS SOLUTIONS FEEL SLIPPERY.

BASES5 GENERAL PROPERTIES

• REACT WITH ACIDS TO PRODUCE SALTS AND WATER.

• CONDUCT ELECTRIC CURRENT.

Svante Arrhenius Theory limitedto aqueoussolutions

ARRENHIUS ACIDS & BASES

• ARRENHIUS ACID:

INCREASES THE CONC.

OF HYDROGEN IONS, H+, IN AQUEOUS SOLUTIONS

ARRENHIUS ACIDS & BASES

• ARRENHIUS BASE:

INCREASES THE CONCENTRATION

OF HYDROXIDE IONS, OH-, IN AQUEOUS SOLUTIONS

AQUEOUS SOLUTIONS OF BASES

• ALKALINE• IONIC HYDROXIDES WHICH

DISSOCIATE IN SOLUTION TO RELEASE OH- (aq).

• SODIUM HYDROXIDE: NaOHNaOH (s) Na+ (aq) + OH- (aq)

Group 1 HydroxidesNaOHKOHLiOHRbOHCsOH

Group 2 HydroxidesCa(OH)2

Ba(OH)2

Sr(OH)2

AnotherACID-BASE THEORIES

• ARRENHIUS DEFINITION REQUIRES SUBSTANCES TO BE AQUEOUS.

• DEFINITIONS REVISED TO INCLUDE SUBSTANCES WHEN THEY ARE NOT IN A WATER SOLUTION.

BRONSTED-LOWRY ACIDS & BASES

• BRONSTED-LOWRY ACID:

A MOLECULE or ION THAT IS A

PROTON DONOR.

• HCl + NH3 NH4+ + Cl-

• HCl transfers a proton to the ammonia molecule

Figure 14.3The Reaction of NH3 with HCl to Form

NH4+ and Cl-

BRONSTED-LOWRY BASE

• MOLECULE OR ION THAT IS A PROTON ACCEPTOR.

The Reaction of NH3 with HCl to Form NH4

+ and Cl-

AMMONIA ACCEPTS A PROTON FROM HCl thus AMMONIA IS A BRONSTED-LOWRY BASE

BONSTED-LOWRY ACID-BASE REACTION

• PROTONS ARE TRANSFERRED FROM ONE REACTANT (THE ACID)

TO ANOTHER (THE BASE).

ACID-BASE REACTIONS• BRONSTED-LOWRY ACID DONATES A

H+

• SPECIES REMAINING COULD RE-ACCEPT THAT H+ AND THUS ACT AS A BASE

CONJUGATE BASE

• SPECIES THAT REMAINS AFTER A BRONSTED-LOWRY ACID HAS GIVEN UP A H+ ION.

• HF (aq) + H2O (l) F- (aq) + H3O+ (aq)

acid conjugate

base

• BRONSTED-LOWRY BASE ACCEPTS A H+

• SPECIES REMAINING COULD RE-DONATE THAT H+ AND THUS ACT AS AN ACID

CONJUGATE ACID

• SPECIES THAT FORMS AFTER A BRONSTED-LOWRY BASE HAS ACCEPTED A H+ ION.

• HF (aq) + H2O (l) F- (aq) + H3O+ (aq)

base conjugate

acid

BRONSTED-LOWRY ACID-BASE REACTIONSAre equilibrium systems meaning that both theForward and the reverse reactions occur.

Each contain two conjugate acid-base pairs.

Let’s identify the Conjugate Acid-Base Pairs

HNO3 (l) + H2O (l) H3O+ (aq) + NO3- (aq)

Conjugate Acid/Base Pairs

•HA(aq) + H2O(l) H3O+(aq) + A(aq) conj conj conj conj

acid 1 base 2 acid 2 base 1

DO PROBLEM 48 on page 625

AMPHOTERIC COMPOUNDS

• SPECIES THAT CAN ACT AS EITHER AN ACID OR A BASE

H2SO4(aq) + H2O H3O+(aq) + HSO4- (aq)

base

NH3 (g) + H2O (l) NH4+(aq) + OH- (aq)

acid

Water as an Acid and a Base

•Water is amphoteric (it can behave either as an acid or a base).

• H2O (l) + H2O(l) H3O+ + OH

• conj conj– acid 1 base 2 acid 2 base 1

MONOPROTIC ACIDS

• ACIDS THAT CAN DONATE ONLY ONE HYDROGEN ION PER MOLECULE.

• EXAMPLES

HCl

HNO3

HClO4

Polyprotic Acids

• . . . can furnish more than one Hydrogen ion (H+) to the solution.

• Examples:

• H2SO4

• H3PO4

All polyprotic acids ionize in a stepwiseManner i.e., one HYDROGEN ION at a time.

H2SO4 (l) + H2O (l) H3O+ (aq) + HSO4- (aq)

HSO4- (aq) + H2O (l) H3O+ (aq) + SO4

2- (aq)

Each step is weaker than the one before; therefore, concentration of ions formed in the first step is the greatest.

POLYPROTIC ACIDS

• DIPROTIC ACID:

CAN DONATE TWO HYDROGEN IONS PER MOLECULES.

• TRIPROTIC ACID:

CAN DONATE THREE

HYDROGEN IONS

PER MOLECULE

Lewis Acids and BasesEmphasizes role of electron pairs to form a

covalent bond

• Lewis Acid: electron pair acceptor

• Lewis Base: electron pair donor

Al3+ + 6H

OH

Al OH

H6

3+

The Al(H2O)63+ ion

Aluminum ion (Lewis Acid) accepts electron pairs From Water (Lewis Base) donates electron pairsto form covalent bonds.

Lewis Acid-Base Reaction:

formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor.

LEWIS DEFINITION BROADEST OF THETHREE ACID-BASE DEFINITIONS

STRONG ACIDS

• ACID THAT IONIZES COMPLETELY IN AQUEOUS SOLUTION.

STRONG ACID Solutions

HClO4 (aq)

H2SO4 (aq)

HNO3 (aq)HCl (aq)HBr (aq)HI (aq)

MEMORIZE!!!

WEAK ACIDS

• ACID THAT IONIZES LESS THAN COMPLETELY IN AQUEOUS SOLUTION.

• . Ka is the acid dissociation constant.• Smaller the Ka the weaker the acid.

Figure 14.4Graphic Representation of the Behavior of Acids of Different Strengths in Aqueous Solution

a) Strong Acid

b) Weak Acid

Figure 14.6

A Strong Acid (a) and a Weak Acid (b) in Water

Bases•“Strong” and “weak” are used in the same sense for bases as for acids.

•strong = complete dissociation (hydroxide ion supplied to solution)

•NaOH(s) Na+(aq) + OH(aq)

Strong Bases (Strong electrolytes)

Group 1A HydroxidesNaOHKOHLiOHRbOHCsOH

Group 2A HydroxidesCa(OH)2

Ba(OH)2

Sr(OH)2

WEAK BASES (Weak electrolytes): Weak = incomplete dissociation

Kb is the base dissociation constant.Smaller the Kb the weaker the base.

NH3 ammoniaCH3NH2 methylamine

Other organic compounds that containnitrogen atoms.