Acid and Base Acid and Base DefinitionsDefinitionsAcid and Base Acid and Base DefinitionsDefinitions

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Acid and BasesAcid and Bases

Acid and BasesAcid and Bases

Acid and BasesAcid and Bases

Acids

Have a sour taste. Vinegar is a solution of acetic acid. CitrusHave a sour taste. Vinegar is a solution of acetic acid. Citrusfruits contain citric acid.fruits contain citric acid.

React with certain metals to produce hydrogen gasReact with certain metals to produce hydrogen gas..

React with carbonates and bicarbonates to produce carbon React with carbonates and bicarbonates to produce carbon dioxide gasdioxide gas

Have a bitter taste.Have a bitter taste.

Feel slippery. Many soaps contain bases.Feel slippery. Many soaps contain bases.

Bases

Some Properties of Acids

Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion

attached to a water molecule)

Taste sour

Corrode metals

Electrolytes

React with bases to form a salt and water

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

Anion Ending Acid Name

-ide hydro-(stem)-ic acid

-ate (stem)-ic acid

-ite (stem)-ous acid

Acid Nomenclature Review

No OxygenNo Oxygen

w/Oxygen w/Oxygen

An easy way to remember which goes with which…An easy way to remember which goes with which…

““In the cafeteria, you In the cafeteria, you ATEATE somethingsomething ICICky”ky”

Acid Nomenclature Flowchart

h yd ro - p re fix-ic en d in g

2 e lem en ts

-a te en d in gb ecom es-ic en d in g

-ite en d in gb ecom es

-o u s en d in g

n o h yd ro - p re fix

3 e lem en ts

AC ID Ss ta rt w ith 'H '

• HBr HBr (aq)(aq)

• HH22COCO33

• HH22SOSO33

hydrohydrobromic acidbromic acid

carboncarbonicic acidacid

sulfursulfurousous acidacid

Acid Nomenclature Review

Some Properties of Bases

Produce OHProduce OH-- ions in water ions in water

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and waterReact with acids to form salts and water

pH greater than 7pH greater than 7

Turns red litmus paper to blueTurns red litmus paper to blue “ “BBasicasic BBluelue””

Some Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

Acid/Base definitions

• Definition #1: Arrhenius (traditional)

Acids – produce H+ ions (or hydronium ions H3O+) in water

Bases – produce OH- ions in water

(problem: some bases don’t have hydroxide ions!)

Arrhenius acid is a substance that produces H+ (H3O+) in water

Arrhenius base is a substance that produces OH- in water

Acid/Base Definitions

• Definition #2: Brønsted – Lowry

Acids – proton donor

Bases – proton acceptor

A “proton” is really just a hydrogen atom that has lost it’s electron!

A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor

acid conjugate base

base conjugate acid

ACID-BASE THEORIESACID-BASE THEORIESACID-BASE THEORIESACID-BASE THEORIES

The Brønsted definition means The Brønsted definition means NHNH33 is a is a BASEBASE in water — and in water — and water is itself anwater is itself an ACIDACID

BaseAcidAcidBaseNH4

+ + OH-NH3 + H2OBaseAcidAcidBase

NH4+ + OH-NH3 + H2O

Amphoteric Substances

• A substance that is amphoteric can act as either an acid or a base.

• In the previous slide, water acted as an acid.• In the following example, water acts as a base.

HCl (g) + H2O (l) H3O+ (aq) + Cl- (aq)

acid base conj. acid conj. base

Conjugate PairsConjugate Pairs

Acid-Base Behavior• Consider a compound having the formula HOX.• If X is highly electronegative, it will have a strong attraction

for the electrons shared with O.– The O, will in turn, pull strongly on the electrons held shared

with H.– This H will then be easily lost = acid

• If X has a low electronegativity, the oxygen will pull the electrons away from X.– The hydrogen will remain joined to the oxygen.– Since the O and H can easily remain together, it is likely that OH-

will be formed = base• Nonmetals tend to have high EN = acids• Metals tend to have low EN = bases

Acids & Base DefinitionsAcids & Base Definitions

Lewis acid - a substance Lewis acid - a substance that accepts an electron that accepts an electron pairpair

Lewis base - a substance Lewis base - a substance that donates an electron that donates an electron pairpair

Definition #3 – Lewis Definition #3 – Lewis

Formation of Formation of hydronium ion hydronium ion is also an excellent is also an excellent example.example.

Lewis Acids & BasesLewis Acids & Bases

•Electron pair of the new O-H bond Electron pair of the new O-H bond originates on the Lewis base.originates on the Lewis base.

HH

H

BASE

••••••

O—HO—H

H+

ACID

Lewis Acid/Base ReactionLewis Acid/Base Reaction

Lewis Acid-Base Lewis Acid-Base Interactions in BiologyInteractions in Biology

• The heme group in The heme group in hemoglobin can hemoglobin can interact with Ointeract with O22 and and CO.CO.

• The Fe ion in The Fe ion in hemoglobin is a hemoglobin is a Lewis acidLewis acid

• OO22 and CO can act as and CO can act as Lewis basesLewis bases

Heme group

HOMEWORK1) Identify the acid, base, conjugate acid, and conjugate base

in the following reactions (using the Bronsted-Lowry definition):

a) HNO3 (aq) + NaOH (aq) H2O (l) + NaNO3 (aq)b) NaHCO3 (aq) + HCl (aq) NaCl (aq) + H2CO3 (aq)

2) What is the conjugate base of each of the following acids?a) H2SO3 c) NH3

b) H2CO3 d) HF

3) Classify each of the following substances as either a Lewis acid or a Lewis base:

a) Cl- c) Na+

b) CO32- d) Br-

MORE HOMEWORK

4) Describe the differences in the three acid-base definitions of this PowerPoint.

5) What are conjugate acids and bases?6) Name the following substances:

a) HCl (aq) b) H2SO4 c) KOH

7) What kind of element would you expect to find in position X of the compound HOX if the compound is determined to be amphoteric?