Balance Redox Rxns:

Fe(OH)3 +

[Cr(OH)4]-1

Fe(OH)2 + CrO4-2

AP CHM HW•Read: Chapter 18

Review the Multiple-Choice

Section of the Midterm.

Electro-chemistry

Metallic Conduction

•The flow of electrons through a metal

Ionic Conduction•The movement of ions (electrolytes) through a solution

•Electrolytic Conduct.

Electrode•The surface or point in which oxidation or reduction takes place

Anode•The electrode where oxidation

takes place

•An Ox (-)

Cathode•The electrode where reduction

takes place

•Red Cat (+)

Voltaic or Galvanic Cell

Electrochemical Cell in which:

a spontaneous oxidation-reduction reaction produces electrical energy

Half-Cell•A cell where only

oxidation or only reduction takes

place

•An electrochemical cell must have two

half-cells connected by a salt

bridge

•A half-cell will not work by itself

•Both half-cells are required

Salt Bridge

1) Allows electrical contact between the two half-cells

2) Prevents mixing of the two half-cell solutions

3) Allows ions to flow maintaining

electrical neutrality

Determining the Redox Rxn & Voltage of an

Electrochemical Cell

Identify all molecules & ions

(reactants) that exist in the

electrolytic cell

1) Determine all possible half-reactions that

could occur in the system

2 ) Look up each half-rxn from

the Std. Redox Tables

3) Record each half-rxn & its

standard voltage

4) Save the oxidation half-rxn that has the highest voltage

5) Save the reduction half-rxn that has the highest voltage

6) Balance the electrons

between the two half-rxns

7) Add the two half-rxns to

obtain the full electrochemical

reaction

7) Add the voltage of each half-rxn to

obtain the std. voltage required

Determine Eo

Zn(s) + 2 Ag+1(aq)

2 Ag(s) + Zn+2(aq)

AP CHM HW•Read: Chapter 18

•Problems: 7 & 15a

•Page: 526

REDOX Shorthand•Zn|Zn+2||Ag+1|Ag ox

red

•Zn||Zn|Zn+2||Ag+1|Ag||Pt an ox red cat

Drill: Determine Shorthand Rxn & voltage when Cu+1 is reacts with solid

potassium

Voltaic Cell Problems

Determine all when a cell with a Cu electrode in CuCl2(aq) is connected

to a cell with a Zn

electrode in ZnBr2(aq)

Determine all when a cell with a Fe electrode in FeCl3(aq) is connected

to a cell with a Mn

electrode in MnCl2(aq)

Determine all when a cell with a Mg electrode in MgCl2(aq) is connected

to a cell with a Au

electrode in AuCl3(aq)

Drill: What is the best

reducing agent on the chart?

Electrolysis•Using electricity to force an, oh fooey, non-spontaneous

electrochemical rxn

Electrolytic Cell

•Chemical cell where electrolysis is being performed

How to determine the Redox Rxn &

voltage of an Electrolytic Cell

Identify all molecules & ions

(reactants) that exist in the

electrolytic cell

1) Determine all possible half-reactions that

could occur in the system

2 ) Look up each half-rxn from

the Std. Redox Tables

3) Record each half-rxn & its

standard voltage

4) Save the oxidation half-rxn that has the highest voltage

5) Save the reduction half-rxn that has the highest voltage

6) Balance the electrons

between the two half-rxns

7) Add the two half-rxns to

obtain the full electrochemical

reaction

7) Add the voltage of each half-rxn to

obtain the std. voltage required

• Determine the rxn that takes place when 1.5 V is passed through two

Pt electrodes in a solution containing

MgI2(aq) & ZnCl2(aq)

AP CHM HW•Read: Chapter 18

•Problems: 23

•Page: 527

• Determine the rxn that takes place when

2.5 V is passed through two Pt electrode in a

solution of NaCl(aq)

Determine the rxn that takes place when

electricity is passed through two Pt

electrode in molten

NaCl

Drill: Determine the rxn that takes place when

electricity is passed through two Pt

electrodes in ZnCl2(aq)

A car battery has lead & lead(IV)oxide electrodes in

an acidified aqueous lead(II)sulfate solution.

Using the book, determine the voltage that can be

produced.

Relating Equations

Go = Ho - TSo

Go = -RTlnKeq

Go = -nFEo

Determine rxn, Eo, Go, & Keq for a

voltaic cell with half-cells containing Ni(s)

in NiCl2(aq) & Sn(s)

in SnCl2(aq).

Nernst Equation

E = Eo - (RT/nF)lnQ

for non-standard conditions

• Determine the voltage of a cell with a silver

electrode in 1.0 M AgNO3 & an iron

electrode in 0.10 M

FeCl2 at 27oC

• Determine the voltage of a cell with a silver

electrode in 1.0 M AgNO3 & a zinc

electrode in 0.010 M

ZnCl2 at 27oC

• Drill: Determine the rxns that take place when 9.65 mA is passed for 2.5 Hrs through two Pt electrodes in a solution containing

MnBr2(aq) & CuF2(aq)

• Determine the voltage of a cell with a copper

electrode in 0.10 M CuI & a zinc electrode

in 1.0 M ZnCl2 at 27oC

• Determine the voltage of a cell with a silver electrode in 0.10 M

AgNO3 & a zinc electrode in 1.0 M

ZnCl2 at 27oC

AP CHM HW•Read: Chapter 18

•Problems: 41

•Page: 528

The test on electrochemistry

will be on ____day.

Electroplating & Electro-purifying

Electrolysis• During electrolysis, oxidation

& degradation would occur at the anode while reduction & electroplating would occur at the cathode

Current Formula• Current = charge/unit time

• Amps = coul/sec

• Amount (mass, volume, moles, etc) can be

determined from the charge

Calculate the mass of copper plated onto the cathode when a 9.65

mAmp current is applied to a solution of CuSO4

for 5.0 minutes.

Calculate the years required to plate 216 kg

of silver onto the cathode when a 96.5

mAmp current is applied to a solution of AgNO3

Drill: Calculate the current required to purify 510 kg of

aluminum oxide in 5.0 hours

Current, Mass, Time Formula:

nFm = MWIt

Check HW

Test Tuesday

Balance the Rxn

KMnO4 + HCl

MnO2 + KClO2

Calculate the time required to electroplate 19.7 mg of gold onto a

plate by passing 965 mA current through a

solution of Au(NO3)3

• Determine the voltage of a cell with a silver

electrode in 5.0 M AgNO3 & an zinc

electrode in 0.25 M

ZnCl2 at 27oC

Determine the rxn that takes place when 1.0 V is passed through

two Pt electrodes in a soln containing NaI(aq)

& CoCl2(aq).

Calculate the time required to gold plate a 2.0 mm

layer onto a plate(SA = 750 cm2) by passing 965 mA current through a

solution of AuCl3

(DAu = 20 g/cm3)

Calculate the time required to purify a 204 kg of ore that is 60.0 % Al2O3 by

applying a 965 kA current through molten ore sample:

Calculate the time required to purify a 32 kg of ore that

is 75.0 % Fe2O3 by applying a 9.65 kA current through molten ore sample:

A voltaic cell with a silver electrode in 0.10 M Ag+ & a zinc electrode in 1.0 M Zn+2

at 27oC is allowed to react for 5.0 mins at 9.65 A.

Calculate: Eo, E, Go, & mass increase of the cathode.

A voltaic cell with a gold electrode in 0.0010 M Au+3 &

a zinc electrode in 10.0 M Zn+2 at 27oC is allowed to react for 5.0 hrs at 9.65 A.

Calculate: Eo, E, Go, & mass increase of the cathode.