Balance Redox Rxns: Fe(OH) 3 + [Cr(OH) 4 ] -1 Fe(OH) 2 + CrO 4 -2 in base

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 E o 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 CuCl 2(aq) is connected to a cell with a Zn electrode in ZnBr 2(aq)

Determine all when a cell with a Fe electrode in FeCl 3(aq) is connected to a cell with a Mn electrode in MnCl 2(aq)

Determine all when a cell with a Mg electrode in Mg(NO 3 ) 2(aq) is connected to a cell with a Au electrode in Au(NO 3 ) 3 (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 MgI 2(aq) & ZnCl 2(aq)

AP CHM HW Read: Chapter 18 Problems: 23 & 24 Page: 526

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 ZnCl 2(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  G o =  H o - T  S o  G o = -RTlnK eq  G o = -nF E o

Determine rxn, E o,  G o, & K eq for a voltaic cell with half- cells containing Ni (s) in NiCl 2(aq) & Sn (s) in SnCl 2(aq).

Nernst Equation E = E o - (RT/nF)lnQ for non-standard conditions

Determine the voltage of a cell with a silver electrode in 1.0 M AgNO 3 & an iron electrode in 0.10 M Fe(NO 3 ) 2 at 27 o C

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 MnBr 2(aq) & CuF 2(aq)

AP CHM HW Read: Chapter 18 Problems: 41 Page: 528

The test on electrochemistry will be on Thursday.

Determine the voltage of a cell with a silver electrode in 1.0 M AgNO 3 & a zinc electrode in M Zn(NO 3 ) 2 at 27 o C

Determine the voltage of a cell with a copper electrode in 0.10 M CuNO 3 & a zinc electrode in 1.0 M Zn(NO 3 ) 2 at 27 o C

Determine the voltage of a cell with a silver electrode in 0.10 M AgNO 3 & a zinc electrode in 1.0 M Zn(NO 3 ) 2 at 27 o C

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 CuSO 4 for 5.0 minutes.

Calculate the years required to plate 216 kg onto the cathode when a 96.5 mAmp current is applied to a solution of AgNO 3

Drill: Calculate the current required to purify 510 kg of aluminum oxide in 5.0 hours

Test Monday

Calculate the time required to electroplate 19.7 mg of gold onto a plate by passing 965 mA current through a solution of Au(NO 3 ) 3

Calculate the time required to gold plate a 2.0 mm layer onto a 250 cm 2 plate by passing 965 mA current through a solution of Au(NO 3 ) 3 (D Au = 20 g/cm 3 )

Calculate the time required to purify a 204 kg of ore that is 60.0 % Al 2 O 3 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 % Fe 2 O 3 by applying a 9.65 kA current through molten ore sample:

Determine the voltage of a cell with a silver electrode in 5.0 M AgNO 3 & an zinc electrode in 0.25 M Zn(NO 3 ) 2 at 27 o C

Drill: A voltaic cell with a silver electrode in 0.10 M Ag + & a zinc electrode in 1.0 M Zn +2 at 27 o C is allowed to react for 5.0 mins at 9.65 A. Calculate: E o, E,  G o, & mass increase of the cathode.

Determine the rxn that takes place when 1.0 V is passed through two Pt electrodes in a 2.0 L soln containing 1.0 M NaI (aq) & 1.0 M CoCl 2(aq). Using 95.5 mA, determine rxn time.