AP CHAPTER 4 OUTLINE
REACTIONS BETWEEN IONS IN AQUEOUS SOLUTIONS
I. Electrolytes and Nonelectrolytes
A. Electrolyte -- a substance that conducts electricity in an aqueous solution
1. Dissociation -- the process in which ionic compounds break up into ions when making a solution
2. Strong Electrolyte -- strong conductor of electricity (100% dissociation)
B. Nonelectrolyte -- a substance that does not conduct electricity in an aqueous solution
1. Most molecular compounds are nonelectrolytes
2. Hydrated -- surrounded by water molecules
II. Equations for Ionic Reactions
A. Ionic Reactions -- reaction between ions in aqueous solutions
1. Molecular equations -- equation with all ions written together as a compound
2. Ionic equations -- equation in which all soluble strong electrolytes are written in "dissociated" form
a. Spectator Ions -- ions that do not take part in a chemical reaction
3. Net Ionic equations -- equation in which all spectator ions are eliminated
B. Criteria for a Balanced Ionic and Net Ionic Equation
1. Atoms balance
2. Net charge balance
Examples:
III. Predicting Reactions that Produce Precipitates
A. Double Replacement Reaction (Metathesis Reaction) -- two ionic compounds exchange ions with each other in solution
1. Precipitation reaction -- metathesis reaction in which a precipitate is formed
B. Solubility Rules!!!
1. All compounds of the alkali metals (Group 1A) are soluble
2. All salts containing NH4+, NO3-, ClO3-, and C2H3O2- are soluble
3. All chlorides, bromides, and iodides (salts containing Cl-, Br-, or I-) are soluble except when combined with Ag+, Pb+2, and Hg2+2 (note the subscript "2")
4. All sulfates (salts containing SO4-2) are soluble except those of Pb+2, Ca+2, Sr+2, Hg2+2, and Ba+2
5. All metal hydroxides (ionic compounds containing OH-) and all metal oxides (ionic compounds containing O-2) are insoluble except those of Group 1A and of Ca+2, Sr+2, and Ba+2
6. All salts that contain PO4-3, CO3-2, SO3-2, and S-2 are insoluble, except those of Group 1A and NH+4
Examples:
IV. Acids and Bases as Electrolytes
A. Common properties of acids -- sour taste, affect color of indicators (litmus turns red), corrode metals
B. Common properties of baes -- bitter taste, slippery, affect color of indicators (litmus turns blue), corrosive
C. Arrhenius Definition of Acids and Bases
1. Acid -- a substance that reacts with water to produce hydronium ions, H3O+
2. Base -- a substance that reacts with water to produce hydroxide ions, OH-, or is able to react with a hydronium ion
3. Acid-Base neutralization -- the combination of H+ and OH- ions to produce water (a salt will always be the second product)
D. Substances that are Acids -- usually are molecular compounds
1. Ionization reaction -- reaction in which ions are formed where none existed before
Acid molecule + H2O --> H3O+ + anion
a. Monoprotic acid -- can furnish one H+ ion
b. Polyprotic acid -- can furnish two or more H+ ions
2. Nonmetal oxides can be acids
a. Called acidic anhydrides -- "without water", react with water to form acids, and then follow the same mechanism as above
E. Substances that are Bases
1. ionic compounds containing OH- or O-2
a. Basic anhydrides -- react with water to form OH- ions
2. molecular compounds
b. react with water to give hydroxide ions (ionization)
Base molecule + H2O --> BaseH+ + OH-
V. Strong and Weak Acids and Bases
A. Strong electrolytes -- electrolytes that break up 100% into ions in water
1. Strong Acids/Bases -- acids/bases that are strong electrolytes
a. Usually ionic metal hydroxides
B. Weak electrolytes -- electrolytes that do not completely ionize in water
1. Weak Acids/Bases -- weak electrolytes
a. Weak bases are usually molecular bases
C. Dynamic (Chemical) Equilibrium -- rate of reverse reaction equals the rate of the forward reaction
VI. Acid-Base Neutralization
A. Acid Salts -- a salts that is not completely neutralized and can furnish another H+ ion
B. Neutralization of a Strong Acid by a Strong Base
1. If salt formed is soluble, then net ionic equation is production of water from H+ and OH- ions
C. Neutralization When One is a Weak Acid or Base
1. Weak acid - Strong Base
a. Net ionic equation is between hydroxide ions and the acid molecules
2. Weak Base - Strong Acid
a. Net ionic equation is between hydrogen ions and the base molecules
VII. Ionic Reactions That Produce Gases
A. Reactions with acids
1. Sulfides --> H2S
2. Carbonates and Bicarbonates --> CO2
3. Sulfites and Bisulfites --> SO2
4. Cyanides --> HCN
B. Reactions with bases
1. Ammonium slats --> NH3
VIII. Predicting When Ionic Reactions Occur
A. A net ionic equaiton will exist when:
1. A precipitate forms
2. Water forms
3. A weak electrolyte forms from a solution of strong electrolytes
4. A gas forms
B. Predicting whether an ionic reaction will occur
1. Write a molecular equation in the form a metathesis reaction
2. Translate equation into an ionic equation
3. Cancel spectator ions (if a net ionic remains, then a net reaction does occur)
IX. Stoichiometry of Ionic Reactions
A. Note - the concentration of a particular ion equals the concentration of the salt multiplied by the number of ions of that kind in one formula unit of the salt
Examples:
B. Chemical Analysis
1. Qualitative analysis -- determine which substances are present
2. Quantitative analysis -- measure the amounts of the various substances
C. Titrations -- used in quantitative analysis
Examples:
Outline based upon:
Brady, J. E., Holum, J. R., Russell, J. W. (2000). Chemistry: The Study of Matter and Its Changes. (3rd ed.). New York: John Wiley & Sons, Inc. pp. 151-185.
