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• Electrolytes, Acids and Bases Problem Set• General Solubilities of Common Compounds
in Water• Guidelines for Identifying Electrolytes and
Nonelectrolytes• Guidelines for Writing Net Ionic Equations• Ionization Constants for Acids and Bases
Aqueous EquilibriaAcids and Bases
Edward A. Mottel
Department of Chemistry
Rose-Hulman Institute of Technology
04/18/23
Electrolytes
• Reading Assignment: • Zumdahl: Chapter 4.9, 7.1
• The degree that a compound dissociates into ions is a measure of its strength, not its concentration.• Strong electrolytes - dissociate virtually
100% into ions, at all concentrations• Weak electrolytes - dissociate less than
50% into ions• Non-electrolytes - do not form ions when
dissolved in a solvent.
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Strong Electrolytes
• Strong Acids
• HCl, HBr, HI, HNO3, H2SO4, HClO4, etc.
• Strong Bases• Group IA hydroxides: NaOH, KOH
• Ca(OH)2, Sr(OH)2, Ba(OH)2
• Most ionic compounds
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Strong Electrolytes
• Soluble Salts• Binary compounds of metal cations with
nonmetal anions• Compounds of metal cations with
polyatomic anions• Ammonium cation with nonmetal or
polyatomic anions.
Which of these are soluble, strong electrolytes?
KCl, Zn(NO3)2, CuSO4, NH4I
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Strong Electrolytes
• Slightly soluble salts• Compounds which have a solubility
product constant (Ksp) are strong electrolytes, but are not very soluble.
• AgCl, BaSO4, Mg(OH)2, etc.
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Weak Electrolytes
• Weak acids, weak bases, and other soluble compounds which do not ionize extensively.
• A weak electrolyte will usually have a dissociation constant associated with it such as Ka or Kb.
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Weak Electrolytes
• Weak Acids
• HCOOH, CH3COOH, HF, HCN, HNO2, H3PO4, H2S, HS–, H2CO3, HCO3
–, etc.
• Weak Bases
• NH3, CH3NH2, N2H4, etc.
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Non-electrolytes
Compounds which dissolve but do not form a significant number of ions.
Most covalent compounds: compounds of two or more nonmetals excluding those which are strong or weak electrolytes.• water, sugar, methanol, ethylene glycol,
etc.
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Solubility is related to theconcentration of the solute
in the solvent
Dissociationis related
to the ability ofthe compoundto form ionsin solution
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Solubility is related to theconcentration of the solute
in the solvent
Dissociationis related
to the ability ofthe compoundto form ionsin solution
Categorize each of thefollowing compounds
in terms of its solubilityand tendency to form ions.
oilNaClsugar
acetic acidCa(OH)2
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Electrolytic Character SolubilityExamples
• Oil -- not very soluble, doesn’t ionize• NaCl -- very soluble and very conductive• Sugar -- very soluble but non-conducting• Acetic acid -- very soluble but poorly
conducting• Calcium hydroxide -- slightly soluble but
the amount that dissolves, completely ionizes in water
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Solubility is related to theconcentration of the solute
in the solvent
Dissociationis related
to the ability ofthe compoundto form ionsin solution
solubleslightlysoluble
strong
weak
non-electrolyte
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Electrolytic Character SolubilityExamples
• Sugar -- very soluble but non-conducting• Acetic acid -- very soluble but poorly
conducting• Calcium hydroxide -- slightly soluble but
the amount that dissolves, completely ionizes in water
• Oil -- not very soluble, doesn’t ionize
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Solubility is related to theconcentration of the solute
in the solvent
Dissociationis related
to the ability ofthe compoundto form ionsin solution
solubleslightlysoluble
strong
weak
non-electrolyte
oil
NaCl Ca(OH)2
sugar
acetic acid CO2
The solubility of a compound does not predictits electrolytic character.
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Equation Notation
Each compound in solution is considered in its “predominant” form with proper annotation:
HCl(aq) H+(aq) + Cl– (aq)
KOH (aq) K+(aq) + OH– (aq)
• Strong Electrolytes as completely dissociated.
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Equation Notation
Each compound in solution is considered in its “predominant” form with proper annotation:• Weak Electrolytes and Non-electrolytes as
molecular compounds
HF(aq) H+(aq) + F– (aq)
CH3OH (aq) H+(aq) + CH3O– (aq)
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Group Activity
Identify the predominant form and write a dissociation reaction for the following compounds• nitric acid• hydrofluoric acid• potassium chlorate• aqueous ammonia• sodium hydroxide
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Equilibrium Arrows
HNO3(aq) H+(aq) + NO3–
(aq)
HF(aq) H+(aq) + F– (aq)
KClO3(aq) K+(aq) + ClO3–
(aq)
NH3(aq) + H2O (l) NH4+(aq) + OH–
(aq)
NaOH (aq) Na+(aq) + OH– (aq)
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Acidity versus Neutralizing Ability
HCl(aq) H+(aq) + Cl– (aq)
CH3COOH (aq) H+(aq) + CH3COO– (aq)
HCl(aq) + OH– (aq) H2O (l) + Cl– (aq)
CH3COOH(aq) + OH–(aq) H2O (l) + CH3COO– (aq)
0.1 M hydrochloric acid is more acidic than 0.1 M acetic acid, but the same volume of each can neutralize the same amount of
base.
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Acid - Base Theories
Theory Acid Base
Arrhenius H+ donor OH– donor
Brønsted-Lowry
H+ donor H+ acceptor
Lewis e– pairacceptor e– pair donor
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Conjugate Acids and Bases
The reaction of an acid and a base produces a conjugate acid and a conjugate base.
HCl(aq) + OH– (aq) H2O(l) + Cl– (aq)
acid base conjugateacid
conjugatebase
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Conjugate Acid-Base Pairs
Acid ConjugateBase
Base ConjugateAcid
HCl HCl
NH3
HCO3–
HCO3– HCO3
–
HCO3–CO3
2– CO32–
H2CO3 H2CO3
NH3 NH4+NH4
+
Cl– Cl–
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Group Activity
Write an equation that demonstrates the acidic character of carbonic acid when it reacts with water.• Assign appropriate equilibrium arrows for
the reaction.• Identify the acid and base.• Identify the conjugate acid and conjugate
base.
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Acid Character of Carbonic Acid
H2CO3(aq) + H2O(l) H3O+(aq) + HCO3–(aq)
acid base conjugateacid
conjugatebase
Which is the acid, which is the base?
Which way does the equilibrium arrow point?
What are the products of this reaction?
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Group Activity
Determine how the bisulfide ion (HS–)• can behave as an acid in water.• can behave as a base in water.
Write an equation for each reaction as it demonstrates its acid or base character.
If possible, assign appropriate equilibrium arrows for each reaction.
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Acid-Base Character of Bisulfide Ion
HS–(aq) + H2O(l)
acid base
H3O+(aq) + S2–(aq)
HS–(aq) + H2O(l)
base acid
OH–(aq) + H2S(aq)
conjugateacid
conjugatebase
conjugatebase
conjugateacid
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Group Activity
For each of the following species determine• if it can behave as an acid.• if it can behave as a base.
Write an equation for each species as it demonstrates its acidic or basic character.
If possible, assign appropriate equilibrium arrows for each reaction.
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Determine the Acid-Base Character
H2CO3
OH–
K+
F–
HS–
H2O
NH4+
SO42–
Which of these species can act as an acid,which can act as a base, which can act as both?
Write an equation that shows each characterand justify your answer.
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