Reactions and Equations

Redox Reaction Basics, Part 1

(1 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Foglino, Paul. "Oxidation-Reduction and Electrochemistry." Cracking the AP Chemistry Exam. Ed. Rebecca Lessem. New York, NY: Random House, 2010. Print.

Reactions and Equations

Redox Reaction Basics, Part 2

(2 of 19)

Foglino, Paul. "Oxidation-Reduction and Electrochemistry."Cracking the AP Chemistry Exam. Ed. Rebecca Lessem. New York, NY: Random House, 2010. Print.

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Redox Reactions—Oxidation State Rules,

Part 1

(3 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Redox Reactions—Oxidation State Rules,

Part 2

(4 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Oxidation-reduction (redox) reactions occur when electrons are transferred between reactants.

Oxidation states or numbers indicate the number of electrons gained or lost when a bond is formed.

An element is oxidized when it loses electrons.

An element is reduced when it gains electrons.

Remember: LEO (lion) GER

Lose Electrons Oxidation; Gain Electrons Reduction

Or OIL RIG: Oxidation Is Losing electrons;

Reduction Is Gaining elections

When one substance is oxidized, another must be reduced.

Reducing agents are oxidized. Their oxidation numbers increase.

Oxidizing agents are reduced. Their oxidation numbers decrease.

An activity series is a list of metals in order of decreasing ease of oxidation. Any metal can be oxidized by the ions of metals listed below it.

1. Elements have an oxidation number of 0.

2. Monatomic ions have an oxidation number equal to their charge.

3. Nonmetals have negative oxidation numbers.

-Oxygen’s oxidation number is -2 except in peroxides (O22-) , in which case it is -1.

-Hydrogen’s oxidation number is +1 with nonmetals and -1 with metals.

4. The halogens are -1 in most binary compounds, but positive when combined with oxygen (except fluorine).

5. The sum of oxidation numbers in a neutral compound is 0.

6. The sum of oxidation numbers in a polyatomic ion is the charge of the ion.

Reactions and Equations

Redox Reactions—Half Reactions

(5 of 19)

Foglino, Paul. "Oxidation-Reduction and Electrochemistry."Cracking the AP Chemistry Exam. Ed. Rebecca Lessem. New York, NY: Random House, 2010. Print.

Reactions and Equations

Acid-Base Reactions—Need to Know Concepts

(6 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Acid-Base Reactions

(7 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Acid-Base Reactions—Lewis Acids and Bases

(8 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Half reactions are used to balance and complete the redox reaction. One shows reduction, and one shows oxidation.

Example:

Fe + 2HCl  FeCl2 + H2

Oxidation: Fe Fe2+ + 2e-

Reduction: 2H+ + 2e- H2

coordination complexes: involves a metal ion being bonded to surrounding molecules or ions that act as ligands

amphoterism: the ability of something to act as an acid or a base

An acid-base reaction is a double replacement reaction which:

~has 4 ions in reactants

~at least one product that is a gas, water, or not soluble

Acid/base reactions have a strong or weak acid/base in them.

______

Example Reaction:

NH3+BF3 NH3BF3

Lewis acid: an electron-pair acceptor

-typically contain an incomplete octet of electrons

Ex. H+ , BF3 , Fe3+

Lewis base: an electron-pair donor

Ex. OH- , NH3 , CN-

Reactions and Equations

Acid-Base Reactions—Bronsted-Lowry Bases and Acids

(9 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Acid-Base Reactions—Arrhenius Acids and Bases

(10 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Electrochemistry—Electrolytic and Galvanic Cells, Part 1

(11 of 19)

Geod, Francis. "Comparing Electrochemical to Electrolytic Cells." saskschools. N.p., n.d. Web. 14 Apr 2011. < sson3/comparing.html>.

Reactions and Equations

Electrochemistry—Electrolytic and Galvanic Cells, Part 2

(12 of 19)

Geod, Francis. "Comparing Electrochemical to Electrolytic Cells." saskschools. N.p., n.d. Web. 14 Apr 2011. < sson3/comparing.html>.

Basic Bronsted-Lowry Reaction

HX + H2O  X- + H3O+

Bronsted-Lowry acid: a substance that acts as a proton donor; Ex. HCl,

Bronsted-Lowry base: a substance that acts as a proton acceptor; Ex. NH3

Example Reaction

HCl + H2O H3O+ + Cl-

Arrhenius acid: a substance that creates H+ ions when dissolved in water; Ex. HCl

Arrhenius base: a substance that creates OH- ions when dissolved in water; Ex. NaOH

The cells are created typically with two half cells. Each has an electrode (anode and cathode) inside an electrolyte. The electrons migrate from the anode to cathode via a porous bridge connecting the electrolytes. Reduction occurs at the cathode, oxidation occurs at the anode.

Electrochemical cells can either create electrical energy through spontaneous redox reactions (galvanic cells) or cause redox reactions through induction (electrolytic).

electrolytic / galvanic
cathode / - charge / + charge
anode / + charge / - charge
voltage / - voltage / + voltage
spontaneous? / no / yes

Reactions and Equations

Electrochemistry—Faraday’s Laws

(13 of 19)

Kuznetsoz, A. "Faraday’s Laws of Electrolysis." The Free Dictionary. N.p., n.d. Web. 14 Apr 2011.

Reactions and Equations

Electrochemistry—Half-Cell Potentials

(14 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Electrochemistry—Half-Cell Potentials

(15 of 19)

Brown, Theodore, LeMay, et. al. "Oxidation-ReductionReactions." Chemistry: The Central Science. Ed. Nicole Folchetti. Upper Saddle River, NJ: Pearson Education, 2009. Print.

Reactions and Equations

Precipitation Reactions—Characteristics

(16 of 19)

Brown, Theodore. Chemistry - The Central Science: Ap Test Prep. 11. Upper Saddle River, NJ: Pearson, 2008. 124,750-51. Print.

"Precipitation Reactions." Foundations of Chemistry. University of Memphis, n.d. Web. 14 Apr 2011.<

They are quantitative laws describing the relationship between the mass and nature of chemical substances and the amount of electricity passed through the electrolyte.

The first law states that the mass of the product at an electrode is directly proportional to the amount of electricity (coulombs) transferred at the electrode.

The second law states that the mass of the product, at a constant quantity of electricity, is directly proportional to the product’s equivalent weight.

Emf depends on the cathode and anode half cells. Each cell is assigned a voltage that is the potential for reduction to occur at that electrode. Therefore, emf can be determined with: (cathode half cell potential) - (anode half cell potential).

Knowing the half-cell potentials, one can determine the direction of the reaction. Using the above equation, a negative emf value means that the reaction is reactant favored and non-spontaneous. If the emf is positive, the reaction is product favored and spontaneous.

The above equation however, is only under standard conditions. When the reaction happens under non-standard conditions (not 25*C, varying concentrations, etc.) then we must use the Nernst equation to calculate emf:

E = E* - [(R x T) / (n x F)] x lnQ

where:

E = emf under nonstandard conditions

E* = emf under standard conditions

R = ideal gas constant (J/mol-K)

T = temperature in kelvin

n = # of e- transferred in the reaction

F = faraday’s constant

Q = the reaction quotient

Occurs when two oppositely charged ions attract each other and form an insoluble solid.

Always is a double replacement reaction.

If Q > Ksp precipitation occurs until Q = Ksp

Reactions and Equations

Precipitation Reactions—Terms, Part 1

(17 of 19)

Brown, Theodore. Chemistry - The Central Science: Ap Test Prep. 11. Upper Saddle River, NJ: Pearson, 2008. 124,750-51. Print.

Reactions and Equations

Precipitation Reactions—Terms, Part 2

(18 of 19)

Brown, Theodore. Chemistry - The Central Science: Ap Test Prep. 11. Upper Saddle River, NJ: Pearson, 2008. 124,750-51. Print.

Reactions and Equations

Precipitation Reactions—Examples

(Note: Equations are not written this way on the Free Response Equations Section of the AP Exam)

(19 of 19)

Brown, Theodore. Chemistry - The Central Science: Ap Test Prep. 11. Upper Saddle River, NJ: Pearson, 2008. 124,750-51. Print.

"Precipitation Reactions." Foundations of Chemistry. University of Memphis, n.d. Web. 14 Apr 2011.<

Precipitation ReactionsReaction that results in the formation of an insoluble product

PrecipitateAn insoluble solid formed by a reaction in solution

InsolubilityNot capable of being fully dissolved

Metathesis ReactionsA reaction that occurs in which two substances react through an exchange of their component ions

Selective PrecipitationSeparation of ions in an aqueous solution by using a reagent that forms a precipitate with one of the ions

AgNO3 (aq) + KCl(aq) AgCl(s) + KNO3(aq)
LiBr (aq) + AgNO3 (aq)LiNO3 (aq) + AgBr (s) / / LiNO3 (aq) + AgBr (s)

2 K3PO4 (aq) + 3 MgCl2 (aq)Mg3(PO4)2 (s) +6 KCl (aq)

Pb2+(aq) + 2I-PbI(aq)