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Chapter 14Acids & Bases
14.1 Properties of Acids and Bases
Properties of Acids1. Aqueous solutions have a sour taste 2. Some acids react with active metals to release
hydrogen:
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
3. Acids react with bases to produce salts and water:
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
4. Acids conduct electric current
Properties of Acids5. Acids change the color of acid-base
indicators:
Blue litmus turns red
Methyl orange turns red
6. Have a pH of less than 7
7. Donate protons, H+
8. React with carbonates
9. Neutralize bases
Review: Acids Nomenclature• Binary acids - acids that contain two different
elements: hydrogen and one of the more-electronegative elements • prefix "hydro-" • Root of element name • "-ic" ending
• example: HBr = hydrobromic acid • Oxyacids - compounds of hydrogen, oxygen,
and a third element, usually a nonmetal – no prefixes
Some Common Industrial Acids• Sulfuric AcidHighest volume production
of any chemical in the U.S. Used in the production of
paper, fertilizers, petroleum refining & car batteries
Some Common Industrial Acids
• Nitric Acid• Used in the production of rubber,
plastics, pharmaceuticals, fertilizers & explosives
• Nitric acid is a volatile acid – its reactive components evaporate easily
• Stains proteins yellow (including skin!)
Some Common Industrial Acids• Hydrochloric Acid• Used in the pickling of steel• Used to purify magnesium
from sea water• Used to correct swimming
pool pH• Part of gastric juice, it aids in
the digestion of protein• Sold commercially as
“Muriatic acid”
Some Common Industrial Acids
• Phosphoric Acido A flavoring agent in sodaso Used in the manufacture of
detergents & fertilizerso Not a common laboratory reagent
Some Common Industrial Acids
• Acetic AcidConcentrated “glacial” acetic
acid used in the manufacture of plastics
Used in making pharmaceuticalsAcetic acid is the acid present in
vinegar
Properties of Bases1. Aqueous solutions of bases have a bitter
taste 2. Bases change the color of acid-base
indicators Turns red litmus blueTurns phenolphthalein
magenta/purple3. Dilute aqueous solutions of bases feel
slippery 4. Bases react with acids to produce salts
and water 5. Bases conduct electric current 6. Are proton, H+, acceptors7. Have a pH value of greater than 78. Neutralize acids
Arrhenius Acids & Bases
• Arrhenius Acid A chemical compound that increases the concentration of hydrogen ions, H+, in aqueous solution
• Arrhenius BaseA substance that increases the concentration of hydroxide ions, OH-, in aqueous solution Swedish Chemist
Aqueous Solutions of Acids • Acids are molecular compounds that
ionize in solution
HNO3 + H2O → H3O+ + NO3-
H2SO4 + H2O → H3O+ + HSO4-
H2O + HCl → H3O+ + Cl-
Proton Proton DonorDonor
Proton Proton AcceptorAcceptor
Ionization Equations• Instead of:
HCl (g) + H2O (l) → H3O+ (aq) + Cl- (aq)
• Sometimes we write this:
HA + H2O (l) → H3O+ (aq) + A- (aq)
• Or even this:
HCl (aq) → H+ (aq) + Cl- (aq)
Generic formulas
Leave out water
Strength of Acids• Strong acids completely
ionize in solution. (100%)• Weak acids ionize only
slightly and are weak electrolytes.(<5%)
Strong Acid Dissociation
Weak Acid Dissociation
Strength vs. Concentration
• Strength refers to ionization in solution.
• Concentration refers to the amount of solute in solution.
• It is possible to have a concentrated solution of a weak acid or base.
• It is also possible to have dilute solution of a strong acid or base.
Organic AcidsOrganic acids all contain the “carboxyl” group, sometimes several of them.
The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.
Examples of Organic Acids Citric acid in citrus fruit Malic acid in sour apples Deoxyribonucleic acid,
DNA Amino acids, the building
blocks of protein Lactic acid in sour milk
and sore muscles Butyric acid in rancid
butter
Aqueous Solutions of Bases• Ionic bases dissociate when placed in water:
NaOH (s) + H2O (l) → Na+ (aq) + OH- (aq)
• Basic solutions are referred to as “alkaline”• Molecular bases produce hydroxide ions through
a reaction with water:
NH3 (g) + H2O (l) → NH4+ (aq) + OH- (aq)
Strength of Bases
• Strength of ionic bases in related to solubility:
High solubility = strong base
Low solubility = weak base
• Molecular bases tend to be weak regardless of solubility
Chapter 14Acids & Bases
14.2 Acid-Base Theories
Bronsted-Lowry Acids & Bases
• Bronsted-Lowry Acid:
A molecule or ion that is a proton donor• Bronsted-Lowry Base:
A molecule or ion that is a proton acceptor
ex: hydroxide ion is the acceptor portion of the ionic base, not the whole compound itself
• Bronsted-Lowry Acid-Base Reaction:
A reaction in which protons are transferred from the acid to the base.
Types of Acids
• Monoprotic Acids: HC2H3O2
HCl
• Diprotic Acid: H2SO4
• Triprotic Acids: H3C6H5O7
H3PO4
• * Each successive proton is harder to remove!
Can donate 1
H
Can donate 2
Hs
Can donate 3
HsPolyprotic AcidsPolyprotic Acids
Lewis Acids & Bases• Lewis Acid:
An atom, ion or molecule that accepts an electron pair to form a covalent bond
• Lewis Base:An atom, ion or molecule that donates an electron pair to form a covalent bond
• Lewis Acid-Base Reaction:The formation of one or more covalent bonds between an electron-pair donor and electron-pair acceptor. This definition can be applied to phases other than aqueous reactions.
Chapter 14Acids & Bases
14.3 Acid-Base Reactions
Conjugate Acids & Bases• Conjugate Base
The species that remains after an acid has given up its proton
H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq)
The stronger the acid, the weaker its conjugate base
AcidAcid Conjugate Conjugate BaseBase
• Conjugate Acid
The species that is formed when a base gains a proton
H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq)
The stronger the base, the weaker its conjugate acid
Conjugate Acids & Bases
BaseBase Conjugate Conjugate AcidAcid
Proton-Transfer Reactions
• These reactions favor the production of the weaker acid and the weaker base.
Amphoteric Compounds
• Any species that can act as either an acid or a base
Ex: Water as a base:
H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq)
Ex: Water as an acid:
NH3 (g) + H2O (l) ↔ NH4+ (aq) + OH- (aq)
Hydroxyl Group in Molecules• The –OH group in a molecule can be acidic or
amphoteric• As the number of oxygens that are bonded around the
atom with the –OH group increases, so does the acidity of the compound.
Oxygens pull Oxygens pull electron density electron density away from the away from the
hydrogen, hydrogen, making it appear making it appear
more positive more positive (and attractive (and attractive to water and to water and other bases)other bases)
Bases Neutralize Acids
Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O
Acids Neutralize Bases
HCl + NaOH NaCl + H2O
Neutralization reactions ALWAYS produce a salt and water.
Acids React with Carbonates
2HC2H3O2 + Na2CO3
2 NaC2H3O2 + H2O + CO2
Neutralization Reactions
• The reaction of hydromium and hydroxide ions to form water molecules
Steps:
1. Dissociation of a base in water
2. Acid donates a proton to water
3. Complete ionic equation
4. Net ionic equation (no spectator ions)
NeutralizationNeutralization
HCl + NaOH HCl + NaOH → NaCl + H→ NaCl + H22OO
Products of NeutralizationHCl + NaOH
H2SO4 + Ca(OH)2
HNO3 + KOH
The products of neutralization are always a ______ and _______.
NaCl + H2O
CaSO4 + 2 H2O
KNO3 + H2O
salt water
Acid Rain• Formation of Acid Rain:
Nonmetallic oxides enter the atmosphere as a result of burning coal, auto exhaust and other forms of air pollution.
Nonmetallic oxides in the air then combine with water to form oxyacids:
SO3 (g) + H2O (l) → H2SO4 (aq)
SOSO22, SO, SO33, CO, CO22, ,
NO, NONO, NO22
Effects of Acid Rain on Marble(calcium carbonate)
George Washington:BEFOREBEFORE
George Washington:AFTERAFTER
CaCOCaCO33 (s)(s) + 2H + 2H33OO++ (aq)(aq) → Ca→ Ca+2+2 (aq)(aq) + CO + CO22 (g)(g) + 3H + 3H22O O (l)(l)