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Announcements• This is a learning experience for us all Thank you for understanding (kinetics, quiz, etc.) Read the book (and handouts on website)!

• Science clarifications Electrons can be in a beaker (solvated electrons) versus protons in a beaker (solvated protons = hydroniums and beyond), but protons are energetically easier to solvate

Salt bridges have spectator ions only

Course websitehttp://faculty.sites.uci.edu/chem2l/chem-h2lcm3lc/

Button cell

CATHODE CAP

MOST COMMON BATTERIES – CLARIFICATION

Separator is the salt bridge; it contains an inert, redox inactive

salt solution (electrolyte)

Dendrites = Shunts

intercalated

Week 6 Objectives

By the end of the week, you will be able to:

• Understand everything that I flew through before

• Use alpha fractions for electrochemical reactions

• Explain how ion‐selective electrodes and pH meters work

• Explain how the solubility product is pertinent to electrochemical reactions

can be; but they are not. Use SHE!

Electrochemical Alpha Fractions

= Ideally polarizable electrodes

Write and explain the line notation for the redox reactionbetween Cu/Cu2+ and an SCE electrode, where Cu2+ is CuSO4(0.1 M), and KCl (1 M) is present in all cells.

Cu SCE

Cu2+(aq) Cu(s)

– –

Pt(s)‐Hg(l) Hg2Cl2(s)


Cu SCE

Cu2+(aq) Cu(s)

– –


Eo(Cu2+/Cu) = +0.1 V vs. SCE


Cu SCE

Cu2+(aq) Cu(s)

– –Eo(Cu2+/Cu) = +0.1 V vs. SCE


Pt(s)‐Hg(l) Hg2Cl2(s)+ Cl–(aq)


Cu SCE

Cu2+(aq) Cu(s)

– –Eo(Cu2+/Cu) = +0.1 V vs. SCE


Pt(s) | Hg(l) | Hg2Cl2(s) | | | Cu2+ | Cu(s)



(b) What is Ecell if [KCl] = 0.1 M?Eo(Cu2+/Cu) = +0.1 V vs. SCE

ln



(a)



ln

0.0592Vlog

1



(a)



ln

0.1V0.0592V

2 log10.1

0.1V 0.0296V 0.0704V



(a)

0.0592Vlog

1



ln

0.1V0.0592V

2 log10.1

0.1V 0.0296V 0.0704V



0.1V0.0592V

2 log1

0.1

0.1V 0.0888V 0.0112V

(a)

(b)

0.0592Vlog

1

EoxEred

Donnan Potential(not a liquid junction

potential)

Frederick G. Donnan(1870–1956)(from Wiki)

Other Types of Electrodes

Membrane and Ion Selective Electrodes (ISEs)

pH Electrode

Ca2+ Electrode

NO3- Electrode

Corning glass membrane

(from Prof. Penner’s Electrochemistry graduate‐level course)

Arnold Orville Beckman(1900–2004)(from Wiki)

porousglass frit


forms a Donnan Potential

ALSO forms a Donnan Potential




(indicator electrode) (reference electrode)



SCE electrode(ideally non-polarizable)

(indicator electrode) (reference electrode)



pH Electrode

Ca2+ Electrode

NO3- Electrode

Polymer (PVC)membrane electrode containing a calcium ionophore



pH Electrode

Ca2+ Electrode

NO3- Electrode

Polymer (PVC)membrane electrode containing a nitrate ionophore

General ion-selective-electrode specifics

Ca2+ electrode NO3– electrodeIon Range 5x10-6 – 1 M 7x10-6 – 1 MpH Range 3 – 10 2.5 – 11

Interfering Ions various M2+ various A–

Electrode slope +28 mV/decade -56 mV/decade


For nitrate

Thermo Scientific, ISE Manuals





How can we deal with interfering ions? Remove them!





How can we deal with interfering ions? Remove them!

Why is the electrode slope +28 and -56 mV per decade?The Nernst equation


For nitrate1–



For calcium2+


Potentiometric Titrations and Solubility Equilibria/Product

Berger, J. Chem. Educ., 2012, 89, 812–813

Reduction: Ag+ Ago

Oxidation: Cuo Cu2+Ag indicator electrode



Reduction: Ag+ Ago


Excess Cl–

Excess Ag+



Reduction: Ag+ Ago


Excess Cl–

Excess Ag+

1 23

(1) Ksp = (tiny) (large)(2) Ksp = (large) (tiny)(3) Ksp = (tiny) (tiny) = (tiny)2

Thus, Ksp = [Ag+]2

DISCUSSION TIME!Pourbaix diagrams are useful for identifying which material is present/stable

from Wiki

Marcel Pourbaix(1904–1998)

http://corrosion‐doctors.org/Biographies/PourbaixBio.htm


from Wiki

RHE

Eo(O2/H2O)




from Wiki

RHE

Eo(O2/H2O)

(1) What is the electrocatalyst for O2 evolution through water oxidation?(2) At what pH values is an electrocatalyst for H2 evolution stable?




from Wiki

(1) What is the electrocatalyst for O2 evolution through water oxidation? MnO2(2) At what pH values is an electrocatalyst for H2 evolution stable?

RHE

Eo(O2/H2O)




from Wiki

(1) What is the electrocatalyst for O2 evolution through water oxidation? MnO2(2) At what pH values is an electrocatalyst for H2 evolution stable? pH > 7.5

RHE

Eo(O2/H2O)



Week 6 Objectives

By the end of the week, you will be able to:

• Understand everything that I flew through before

• Use alpha fractions for electrochemical reactions

• Explain how ion‐selective electrodes and pH meters work

• Explain how the solubility product is pertinent to electrochemical reactions

LectureWeek6-SAA.pdfLectureWeek6-SAA.pdfBinder4.pdfUpdates for LectureWeek6.pdfLectureWeek6-SAA.pdfLectureWeek5-SAA.pdfLectureWeek5-SAA.pdfUpdates for LectureWeek5.pdfLectureWeek5-SAA.pdfLectureWeek5-SAA.pdfLectureWeek5-SAA.pdfUpdates for LectureWeek5.pdfLectureWeek5-SAA.pdfLectureWeek5-SAA.pdfUpdates for LectureWeek5.pdfLectureWeek5-SAA.pdfUpdates for LectureWeek5.pdfLectureWeeks5and6-SAA.pdfLectureWeeks5and6-SAA.pdfLectureWeeks5and6-SAA.pdfUpdates for LectureWeek5.pdf

Updates for LectureWeek5.pdfLectureWeek5-SAA.pdfUpdates for LectureWeek5.pdfLectureWeeks5and6-SAA.pdfLectureWeeks5and6-SAA.pdfLectureWeeks5and6-SAA.pdfUpdates for LectureWeek5.pdf


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