Oxidation Numbers, ox #

are _____ or _____ numbers assigned to each _______ or

____ assuming that the _____________ are transferred

________________ from the ______ electronegative

element to the _______ electronegative element.

________________ now mimic ________ systems.

ox# are written _______ followed by _________ and are

assigned using the following:

Oxidation Number Rules

The ox# of an ______ in it’s pure form, (eg. Pb(s), O2(g) )

is ____.

The ox# of a ____________ _____ is equal to the _________ on that ______.

eg. Cl1-

The algebraic ____ of the oxidation numbers in a ________ polyatomic compound is ___.

eg. Mg3N2 Fe(NO3)3

The most common ox# for O is ___, in peroxides it is ___,

and in compounds with fluorine it is ___. The most common ox# of H is ___, in metal hydrides it is

___. The algebraic ______ of the oxidation numbers in a

polyatomic _____ is equal to the _________ on the ____.

eg. Cr2O

7

2-

Assign the ox# to the most _______________ element __ Determine the ______ charge for that element Considering the charge on the ion or neutral compound,

find the total charge for the other element, then its ox #. In compounds of _______________, the ox# of the

______ electronegative atom is ______ and the ox# of the

______ electronegative atom is _______.

eg. CO2 In a covalent bond, the more ________________ atom

takes _____ the ____________ in the bond.

Energy Transfer Theory

Chemical reactions _________ with the ______________

of __________.

Often, this energy is _____ noticeable as it doesn’t

involve a ___________ change or the production of

________ or _______.

This is true of ____________ reactions, where the

___________ switch between entities with no

___________ change in _________.

To examine the energy ____________ we _________ the

chemical reaction into ___ separate reactions called _____

____________.

For:

Net ionic equation

Half reactions

The energy _________ is the electron ______________ –

______________

Redox reactions require the ______________ reaction

_________________________ to occur simultaneously

with the _______________ reaction

_________________________

Redox – ____________________________

_________ goes __________

______ _______

Balancing REDOX Reactions 1. Assign ___________ ____________ (ox. #) to ______ element in the

rxn and __________ the species being ____________ and ____________.

2. Write separate ______ ____________ (1/2 rxn), for the

______________ (ox.) and _____________ (red.) processes. 3. Balance the ___________ that undergo _____________ or

______________. 4. Add the total _________ gained or lost in _______ ox. or red. rxn.

5. Multiply each _________ so that once combined, the total # of e-s ______ out.

6. Combine the _________. 7. Balance the net ___________ (due to ions) using _____ ions to one

side (for acidic sol’n) or with _______ ions (for basic sol’n). 8. Add _______ to balance ____ and ____. 9. Check that the final eq’n is ________________.

Predicting Redox Reactions

Redox Rxn

occur due to the ____________ of e- from ________

substance to _______________.

is a ________________ of e- between _____________.

if ______ substance ________ e- from another, a

_______________________ rxn _____________. eg. Cu + 2Ag+ ↔ Cu2+ + 2Ag

Reducing agents (RA)

a substance that __________ e- to another substance and

undergoes __________________. Oxidizing agents (OA)

a substance that __________ e- to another substance and

undergoes __________________. eg. Cu + 2Ag+ ↔ Cu2+ + 2Ag

rxns are listed as ____________, S = Strong, W = Weak.

SOA OA1 + ne- ↔ RA1 WRA

WOA OA2 + ne- ↔ RA2 SRA spontaneous rxns occur only if the ______ is

____________ and to the _________ of the ______. For spontaneous rxn:

eg. Will a mixture of aqueous chromium (II) nitrate and tin (II) nitrate react and if so what is the overall equation?

List all species ________ determine the ________, _____________ on the _______ and the ________, ________ on the _________ on the REDOX table

eg. Create ½ rxns from the following reaction data and place in order of strongest to weakest OA:

Ion/metal Zn Pb Ag I1-

Zn2+

Pb2+

Ag+

I2

eg. Create ½ rxns from the following reaction data and place in order of strongest to weakest OA:

Cu2+ + Pb Cu + Pb2+ Ag + Br2 AgBr

Ag+ + Cu Ag + Cu2+ Au + Br2 no rxn

eg. Create ½ rxns from the following reaction data and place in order of strongest to weakest OA:

W + M2 W2+ + M1- Y2+ + Z Y + Z2+

X + M2 no rxn W + Y2+ no rxn

X2+ + Z X + Z2+

Standard Reduction Potentials ( also p 805) E° (volts)

F2 + 2 e- 2 F-1 +2.87

S2O82- + 2 e- 2 SO4

2- +2.01

Co3+ + e-1 Co2+ +1.81

Pb4+ + 2 e-1 Co2+ +1.80

H2O2 + 2 H+ + 2 e- 2 H2O +1.77

Au+ + e-1 Au +1.69

PbO2 + SO42- + 4 H+ + 2 e- PbSO4 + 2 H2O +1.69

MnO41- + 8 H+ + 5 e- Mn2+ + 4 H2O +1.51

Au3+ + 3 e- Au +1.50

Ce4+ + e-1 Ce3+ +1.44

ClO41- + 8 H+ + 8 e- Cl1- + 4 H2O +1.39

Cl2 + 2 e- 2 Cl- +1.36

2 HNO2 + 4 H+ + 4 e- N2O + 3 H2O +1.30

Cr2O72- + 14 H+ + 6 e- 2 Cr3+ + 7 H2O +1.23

O2 + 4 H+ + 4 e- 2 H2O +1.23

MnO2 + 4 H+ + 2 e- Mn2+ + 2 H2O +1.22

2 IO31- + 12 H+ + 10 e- I2 + 6 H2O +1.20

Br2 + 2 e- 2 Br-1 +1.07

AuCl41- + 3 e- Au + 4 Cl- +1.00

Hg2+ + 2 e- Hg +0.85

ClO1- + H2O + 2 e- Cl1- + 2 OH-1 +0.84

Ag+ + e- Ag +0.80

NO31- + 2 H+ + e- NO2 + H2O +0.80

Hg22+ + 2 e- 2 Hg +0.79

Fe3+ + e- Fe2+ +0.77

O2 + 2 H+ + 2 e- H2O2 +0.70

MnO41- + 2 H2O + 3 e- MnO2 + 4 OH-1 +0.60

I2 + 2 e- 2 I- +0.54

Cu+ + e- Cu +0.52

O2 + 2 H2O + 4 e- 4 OH- +0.40

Cu2+ + 2 e- Cu +0.34

SO42- + 4 H+ + 2 e- SO2 + 2 H2O +0.18

SO42- + 4 H+ + 2 e- H2SO3 + H2O +0.17

Sn4+ + 2 e- Sn2+ +0.15

Cu2+ + e- Cu+ +0.15

S + 2 H+ + 2 e- H2S +0.14

AgBr + e- Ag + Br-1 +0.07

2 H+ + 2 e- H2 +0.00

Fe3+ + 3 e- Fe -0.04

Pb2+ + 2 e- Pb -0.13

Sn2+ + 2 e- Sn -0.14

AgI + e- Ag + I-1 -0.15

Ni2+ + 2 e- Ni -0.26

Co2+ + 2 e- Co -0.28

H3PO4 + 2 H+ + 2 e- H3PO3 + H2O -0.28

Tl+ + e- Tl -0.34

PbSO4 + 2 e- Pb + SO42- -0.36

Se + 2 H+ + 2 e- H2Se -0.40

Cd2+ + 2 e- Cd -0.40

Cr3+ + e- Cr2+ -0.41

Fe2+ + 2 e- Fe -0.45

S + 2 e- S2- -0.48

Ga3+ + 3 e- Ga -0.53

Ag2S + 2 e- 2 Ag + S2- -0.69

Cr3+ + 3 e- Cr -0.74

Zn2+ + 2 e- Zn -0.76

Te + 2 H+ + 2 e- H2Te -0.79

2 H2O + 2 e- 2 OH-1 + H2 -0.83

Cr2+ + 2 e- Cr -0.91

Se + 2 e- Se2- -0.92

SO42- + H2O + 2 e- SO3

2- + 2 OH-1 -0.93

Te + 2 e- Te2- -1.14

Mn2+ + 2 e- Mn -1.18

V2+ + 2 e- V -1.19

Al3+ + 3 e- Al -1.66

Ti2+ + 2 e- Ti -1.75

Mg2+ + 2 e- Mg -2.37

Ce3+ + 3 e- Ce -2.48

Na+ + e- Na -2.71

Ca2+ + 2 e- Ca -2.87

Ba2+ + 2 e- Ba -2.91

Cs2+ + 2 e- Cs -2.92

Ra2+ + 2 e- Ra -2.92

K+ + e- K -2.92

Li+ + e- Li -3.00

Electrochemical Cells

(Galvanic, Voltaic, Electric)

the ___________ reactions are occurring _____________

and are _________ by a _______

the e- _________ occurs through this ___________ circuit

the ______ difference ______________ is manifested as

__________ __________.

X+Y+

K+ NO3-

Salt Bridge

As the cell proceeds:

Cathode Anode

mass of electrode

Solution electrical charge

Ions from salt bridge

Cell Shorthand Notation eg. For the Zn/Cu cell: ____________________________ Conventions: the │ notation indicates a phase ______________ where

the _______________ and _________________ are in

physical contact. the ║ notation represents the ______ __________ or

_________ ____________ if additional _____________ are ____________ or

specific ___________ are ___________, they are written

with the _____________ separated by a ___________ or

a _______________. if the cell has no _______ for the electrode, __________

electrodes _________ or __________ are used:

___________________________________________ standard cells are __________ at _________ all ______ sets of information – REDOX equation, cell

diagram and the cell notation are related and if ___ is

provided, the other ____ should be able to be _________.

Calculating Cell Potential, E°cell for each _____ ___________ the ____________

_______________ is listed on the chart on p. 805 or the

reference sheet. the complete ______ is a combination of the

____________ and _____________ half reactions - the

_______ of the two is the _______ potential, _________ this is the usable energy given by:

______________________________________________ as all half reactions are listed as ____________ rxns, the

oxidation reaction ________ the sign, so:

______________________________________________

eg. Calculate the E° cell for the following unbalanced

equation:

Br2 + Cu 2 Br¯ + Cu+

eg. a) Determine the anode, cathode and calculate the standard cell potential produced by a galvanic cell consisting of a Sn

electrode in contact with a solution of Sn2+ ions and a Cr

electrode in contact with a solution of Cr3+ ions.

b) Write the shorthand cell notation.

eg. Use complete half-reactions and potentials to predict whether the following reaction is spontaneous or non-spontaneous in aqueous solutions. If the cell is spontaneous, write the cell shorthand notation.

O2 + 2 SO

2 + 4 OH1- 2 SO

4

2- + 2 H2O

YOU MUST READ 9.6 Corrosion p.710 – 713 before the next lesson

Reactions of Metals with Water The _______ is the _______ and will be ____________.

The ______ and ___________ in it will be the __________.

Need to consider:

i) __________ ________ - _____ of the 3

ii) ________________ _________ this requires a very long ____

_____, or an _______________, as O2 is not very water ________

iii) ________ ______________ - as with ______ ______

• Metals _______ the _____________ _______ _______ will be

________________

That’s why:

• Not ___ metals _______ with __________ ________

eg. ones that _____: ones that ______:

• Not ___ metals _______ with _____________ _______

eg. ones that _____: ones that ______:

• Not ___ metals _______ with _________ ________

eg. ones that _____: ones that ______:

Metals with Metals • Alloys are _______ to change a metal’s ____________. • As _____ _______ undergo ____________ – rust,

corrosion, patina – _______ metals are _______ to stop

the ____________. eg. ___ or ___ need protection. • The ____________ metal, called a ___________ ______,

is ______ on the table _________ to the _______ in

_________. It will __________ the ____________ and

______ the _______.

eg. Which metals will ________ Zn?

eg. Which metals will ____ ________ Zn?

eg. a) Pick a metal that will protect Zn and determine the

cell potential if the cathode is oxygenated water.

b) Do the same for the case where Zn is not protected.

Cells and Spontaneity

Reactants Products

ΔEcell Cell Type Spontaneity

Electrolytic cells, ΔE < 0

requires _____________ source of ______ to ________

the ____ __________ within the cell.

e- are __________ from the _________ and __________

to the ____________ by the ________________. rxn is then the _____________ of the ________________

rxn. used to __________________ and to produce _________

__________. Solution rxns so _____+ could be the ____________

and/or the ____________ reaction.

eg. KI solution and battery

Cathode (red): Erº (V)

Anode (ox): Erº (V)

e- from the __________ (-ve) ____________ of the

_______________ reduce the ________

e- from the _____ flow to the ___________ (+ve) __________ of the ____________ to complete the _____________.

forms ______ and _______ from an ____________ sol’n!

versus

eg. Given the following molten system, AgCl, predict the products at each electrode. Assume inert electrodes and sufficient voltage to cause a reaction to take place. Consider all possible rxns.

eg. Given a 1.00 M solution of ZnI2 at 25°C, predict the anode and

cathode half cell reactions. What is the minimum voltage required for each cell to operate?

Stoichiometry of Cell Reactions

Basic Concepts 1. q = It where:

q = _____________________

I = _____________________

t = _____________________

1C = _______________

2. Faraday’s Law: the ________ of a substance

__________ or ______________ is __________ related to the ____________ transferred

3. Faraday = ___________________________

F = ________________

4.

eg.1 Calculate the amount of charge which passes

through an electrolytic cell with a current of 1.80A for 5.0 min.

eg. 2 Calculate the mass of Zn deposited by a

current of 2.50 A operating over 30.0 min in an electrolytic cell containing Zn(NO3)2(aq).

Free Energy & Electrochemistry ΔGº = ___________ and ΔGº = __________ and… ΔGº = ______________

eg. Calculate ΔGº and Ke for the electrolytic Zn/Al

cell, Zn │ Al3+│Al.

RT

0cell

EnF Keqln