AP Chemistry: Chapter 5-6 Student Notesimages.pcmac.org/.../Documents/ElectrochemFollowAlongNotes.pdf · AP Chemistry: Student Notes ... What amperage is required to plate out 0.250

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AP Chemistry: Student Notes

Objectives

17.1a: Review Redox

Assign Oxidation Numbers to the following:

a. HNO3

b. PbSO4

c. (NH4)2Ce(SO4)3

Balance the following in medium

Al (s) + MnO4- (aq) Al

3+ (aq) + Mn

2+ (aq)

Balance the following in a basic medium

Mg (s) + OCl- (aq) Mg(OH)2 (s) + Cl

- (aq)

17.1a: Review of Redox

17.1: Galvanic Cells

17.2: Standard Reduction Potentials

17.3: Cell Potential and Equilibrium

17.4: The Nernst Equation

17.5--6: Batteries & Corrosion

17.6: Electrolysis

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Balance the following Redox Reaction: The big nasty problem

K4Fe(CN)6 + KMnO4 + H2SO4 KHSO4 + Fe2(SO4)3 + MnSO4 + HNO3 + CO2 +H2O

AP Chemistry—WPHS AP Chem Page 3 3/24/2011

17.1: Galvanic Cells

Review of Redox Reactions

Oxidation: _______________________

Reduction: ___________________________

How to make a __________________ _____________________ (gc)

Which is a _____________________

You need to make separate __________________ for each _____________ reaction.

The problem with this cell is …..

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If you put a ______________ ________________ the cell will produce ___________ for a long time.

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Galvanic Cells: Label All parts

What happens when one of the electrodes is not a metal?

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17.2: Standard Reduction Potentials

Half-reaction E° (V)

Li+ + e

− ⇄ Li(s) −3.0401

Cs+ + e

− ⇄ Cs(s) −3.026

Rb+ + e

− ⇄ Rb(s) −2.98

K+ + e

− ⇄ K(s) −2.931

Ba2+

+ 2 e− ⇄ Ba(s) −2.912

Sr2+

+ 2 e− ⇄ Sr(s) −2.899

Ca2+

+ 2 e− ⇄ Ca(s) −2.868

Na+ + e

− ⇄ Na(s) −2.71

Mg2+

+ 2 e− ⇄ Mg(s) −2.372

Al(OH)4− + 3 e−

⇄ Al(s) + 4 OH− −2.33

Al(OH)3(s) + 3 e− ⇄ Al(s) + 3OH

− −2.31

Al3+

+ 3 e− ⇄ Al(s) −1.66

Ti3+

+ 3 e− ⇄ Ti(s) −1.21

Mn2+

+ 2 e− ⇄ Mn(s) −1.185

2 H2O + 2 e− ⇄ H2(g) + 2 OH

− −0.8277

Zn2+

+ 2 e− ⇄ Zn(s) −0.7618

Cr3+

+ 3 e− ⇄ Cr(s) −0.74

PbO(s) + H2O + 2 e− ⇄ Pb(s) + 2 OH

− −0.58

H3PO2(aq) + H+ + e

− ⇄ P(white[9]) + 2 H2O −0.508

H3PO3(aq) + 2 H+ + 2 e−

⇄ H3PO2(aq) + H2O −0.499

H3PO3(aq) + 3 H+ + 3 e−

⇄ P(red)[9]

+ 3H2O −0.454

Fe2+

+ 2 e− ⇄ Fe(s) −0.44

2 CO2(g) + 2 H+ + 2 e−

⇄ HOOCCOOH(aq) −0.43

Cr3+

+ e− ⇄ Cr

2+ −0.42

AP Chemistry—WPHS AP Chem Page 7 3/24/2011

Cd2+

+ 2 e− ⇄ Cd(s) −0.40

Cu2O(s) + H2O + 2 e− ⇄ 2 Cu(s) + 2 OH

− −0.360

PbSO4(s) + 2 e− ⇄ Pb(s) + SO4

2− −0.3588

PbSO4(s) + 2 e− ⇄ Pb(Hg) + SO4

2− −0.3505

Co2+

+ 2 e− ⇄ Co(s) −0.28

H3PO4(aq) + 2 H+ + 2 e−

⇄ H3PO3(aq) + H2O −0.276

Ni2+

+ 2 e− ⇄ Ni(s) −0.25

MoO2(s) + 4 H+ + 4 e−

⇄ Mo(s) + 2 H2O −0.15

Si(s) + 4 H+ + 4 e−

⇄ SiH4(g) −0.14

Sn2+

+ 2 e− ⇄ Sn(s) −0.13

Pb2+

+ 2 e− ⇄ Pb(s) −0.13

CO2(g) + 2 H+ + 2 e−

⇄ CO(g) + H2O −0.11

HCOOH(aq) + 2 H+ + 2 e−

⇄ HCHO(aq) + H2O −0.03

2 H+ + 2 e− ⇄ H2(g) 0.0000

S4O62−

+ 2 e− ⇄ 2 S2O3

2− +0.08

HgO(s) + H2O + 2 e− ⇄ Hg(l) + 2 OH

− +0.0977

C(s) + 4 H+ + 4 e−

⇄ CH4(g) +0.13

Sn4+

+ 2 e− ⇄ Sn

2+ +0.15

Cu2+

+ e− ⇄ Cu

+ +0.159

HSO4− + 3 H+

+ 2 e− ⇄ SO2(aq) + 2 H2O +0.16

SO42−

+ 4 H+ + 2 e−

⇄ SO2(aq) + 2 H2O +0.17

TiO2+

+ 2 H+ + e

− ⇄ Ti

3+ + H2O +0.19

H3AsO3(aq) + 3 H+ + 3 e−

⇄ As(s) + 3 H2O +0.24

UO2+ + 4 H+

+ e− ⇄ U

4+ + 2 H2O +0.273

Bi3+

+ 3 e− ⇄ Bi(s) +0.32

VO2+

+ 2 H+ + e

− ⇄ V

3+ + H2O +0.34

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Cu2+

+ 2 e− ⇄ Cu(s) +0.340

O2(g) + 2 H2O + 4 e− ⇄ 4 OH

−(aq) +0.40

CH3OH(aq) + 2 H+ + 2 e−

⇄ CH4(g) + H2O +0.50

Cu+ + e

− ⇄ Cu(s) +0.520

CO(g) + 2 H+ + 2 e−

⇄ C(s) + H2O +0.52

I2(s) + 2 e− ⇄ 2 I−

+0.54

H3AsO4(aq) + 2 H+ + 2 e−

⇄ H3AsO3(aq) + H2O +0.56

MnO4− + 2 H2O + 3 e−

⇄ MnO2(s) + 4 OH− +0.59

O2(g) + 2 H+ + 2 e−

⇄ H2O2(aq) +0.70

PtCl42−

+ 2 e− ⇄ Pt(s) + 4 Cl

− +0.758

Fe3+

+ e− ⇄ Fe

2+ +0.77

Ag+ + e

− ⇄ Ag(s) +0.7996

Hg22+

+ 2 e− ⇄ 2 Hg(l) +0.80

Hg2+

+ 2 e− ⇄ Hg(l) +0.85

MnO4− + H

+ + e

− ⇄ HMnO4

− +0.90

2 Hg2+

+ 2 e− ⇄ Hg2

2+ +0.91

Pd2+

+ 2 e− ⇄ Pd(s) +0.915

[AuCl4]− + 3 e−

⇄ Au(s) + 4 Cl− +0.93

MnO2(s) + 4 H+ + e

− ⇄ Mn

3+ + 2 H2O +0.95

[AuBr2]− + e

− ⇄ Au(s) + 2 Br

− +0.96

Br2(l) + 2 e− ⇄ 2 Br

− +1.066

Br2(aq) + 2 e− ⇄ 2 Br

− +1.0873

IO3− + 5 H+

+ 4 e− ⇄ HIO(aq) + 2 H2O +1.13

HSeO4− + 3 H+

+ 2 e− ⇄ H2SeO3(aq) + H2O +1.15

Ag2O(s) + 2 H+ + 2 e−

⇄ 2 Ag(s) + H2O +1.17

ClO3− + 2 H+

+ e− ⇄ ClO2(g) + H2O +1.18

Pt2+

+ 2 e− ⇄ Pt(s) +1.188

ClO2(g) + H+ + e

− ⇄ HClO2(aq) +1.19

2 IO3− + 12 H+

+ 10 e− ⇄ I2(s) + 6 H2O +1.20

ClO4− + 2 H+

+ 2 e− ⇄ ClO3

− + H2O +1.20

O2(g) + 4 H+ + 4 e−

⇄ 2 H2O +1.23

MnO2(s) + 4 H+ + 2 e−

⇄ Mn2+

+ 2H2O +1.23

Cl2(g) + 2 e− ⇄ 2 Cl

− +1.36

Cr2O7− − + 14 H+

+ 6 e− ⇄ 2 Cr

3+ + 7 H2O +1.33

CoO2(s) + 4 H+ + e

− ⇄ Co

3+ + 2 H2O +1.42

2 NH3OH+ + H

+ + 2 e−

⇄ N2H5+ + 2 H2O +1.42

2 HIO(aq) + 2 H+ + 2 e−

⇄ I2(s) + 2 H2O +1.44

Ce4+

+ e− ⇄ Ce

3+ +1.44

BrO3− + 5 H+

+ 4 e− ⇄ HBrO(aq) + 2 H2O +1.45

β-PbO2(s) + 4 H+ + 2 e−

⇄ Pb2+

+ 2 H2O +1.460

α-PbO2(s) + 4 H+ + 2 e−

⇄ Pb2+

+ 2 H2O +1.468

2 BrO3− + 12 H+

+ 10 e− ⇄ Br2(l) + 6 H2O +1.48

2ClO3− + 12 H+

+ 10 e− ⇄ Cl2(g) + 6 H2O +1.49

MnO4− + 8 H+

+ 5 e− ⇄ Mn

2+ + 4 H2O +1.51

HO2• + H

+ + e

− ⇄ H2O2(aq) +1.51

Au3+

+ 3 e− ⇄ Au(s) +1.52

NiO2(s) + 4 H+ + 2 e−

⇄ Ni2+

+ 2 OH− +1.59

2 HClO(aq) + 2 H+ + 2 e−

⇄ Cl2(g) + 2 H2O +1.63

Ag2O3(s) + 6 H+ + 4 e−

⇄ 2 Ag+ + 3 H2O +1.67

HClO2(aq) + 2 H+ + 2 e−

⇄ HClO(aq) + H2O +1.67

Pb4+

+ 2 e− ⇄ Pb

2+ +1.69

MnO4− + 4 H+

+ 3 e− ⇄ MnO2(s) + 2 H2O +1.70

H2O2(aq) + 2 H+ + 2 e−

⇄ 2 H2O +1.78

AgO(s) + 2 H+ + e

− ⇄ Ag

+ + H2O +1.77

Co3+

+ e− ⇄ Co

2+ +1.82

Au+ + e

− ⇄ Au(s) +1.83

BrO4− + 2 H+

+ 2 e− ⇄ BrO3

− + H2O +1.85

Ag2+

+ e− ⇄ Ag

+ +1.98

S2O82−

+ 2 e− ⇄ 2 SO4

2− +2.010

O3(g) + 2 H+ + 2 e−

⇄ O2(g) + H2O +2.075

HMnO4− + 3 H+

+ 2 e− ⇄ MnO2(s) + 2 H2O +2.09

F2(g) + 2 e− ⇄ 2 F−

+2.87

F2(g) + 2 H+ + 2 e−

⇄ 2 HF(aq) +3.05

AP Chemistry—WPHS AP Chem Page 9 3/24/2011

Calculating & Using Electrical Potential

The table above assumes that you have a __________ M solution at ________atm and _________ºC

Example 1: What would be the electrical potential for the reaction:

PbO2 + Na Pb2+

+ Na+

Fe3+

+ Mg Mg2+

+ Fe2+

Example 2:

Is H2(g) capable of reducing Ag+(aq)

Is H2(g) capable of reducing Ni2+

(aq)

Is Fe2+

(aq) capable of reducing VO2+

Is Fe2+

capable fo reducing Cr3+

(aq)

Example 3: Rank the following from strongest oxidizing agent to weakest oxidizing agent:

Ce4+

Ce3+

Fe2+

Fe3+

Mg2+

Mg Ni2+

Sn

AP Chemistry—WPHS AP Chem Page 10 3/24/2011

17.3: Cell Potential and Equilibrium

∆G=-nFEº

Example: Using the data in table 17.1, calculate ∆Gº for the reaction:

Cu2+

(aq) + Fe(s) Cu(s) + Fe2+

(aq)

17.4: The Nernst Equation

What happens when concentration and temperatures are not standard?

Nernst Equation

QnF

RTEE ln

Sometimes written as:

Qn

EE ln0592.0

Assuming 25ºC

Example 1: What is the electrical potential for the following cell with the following concentrations?

VO2+ + Zn Zn

2+ + VO

2+

[VO2+] = 2.0 M [H+] = 0.50 M

[VO2+

] = 1.0 x 10-2

M [Zn2+

] = 0.10 M

First: Write the balanced equation: Use the table of reduction potentials

Second: find Eº

Third: Use the Nernst Equation and plug in the concentration values for Q

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Concentration Cells:

17.4-17.5: Batteries and Corrosion

A Galvanic Cell or a series of galvanic cells hooked together.

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Corrosion

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17.7: Electrolysis

The opposite of a galvanic cell: Pump electricity through a non ___________ reaction.

Comparison of a galvanic cell and an electrolytic cell

Electrolytic Cell ____________________________

Electrolysis __________________________________

Ampere: ___________________________

Faraday ________________________________

The Story of Aluminum

AP Chemistry—WPHS AP Chem Page 14 3/24/2011

Example 1:

Calculate the amount of time required to produce 1000 g of magnesium metal by electrolysis of molten

MgCl2 using a current of 50A.

Example 2:

A Cr3+

(aq) solution is electrolyzed, using a current of 7.60 A. What mass of Cr (s) is plated out after

2.00 days?

What amperage is required to plate out 0.250 mol Cr form a Cr3+

solution in a period of 8.00 hours?

AP Chemistry—WPHS AP Chem Page 15 3/24/2011

Example 3:

What reaction will take place at the cathode and the anode when each of the following is electrolyzed?

a. 1.0 M KF solution

b. 1.0 M CuCl2 solution

c. 1.0 M H2O2 solution containing 1.0 M HCl

10, 122, 299 ---> 162, 5, 122, 60, 60, 188

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AP Style Questions

2002

AP Chemistry—WPHS AP Chem Page 17 3/24/2011

2000