Electrochemistry

21 Sep 2011

How does changing solvent affect redox potential?

Submitted by Sheila Smith, University of Michigan- Dearborn
Evaluation Methods: 

Students are evaluated based on their participation in the in class discussion. Students can be asked a similar test question.

Evaluation Results: 

I suspect that my gen chem students would do better on this exercise (since they are still fully immersed in the topic) than my senior level bioinorganic students, many of whom have forgotten how to balance redox equations. Students did well with the application of the Nernst equation; they seem to retain more about math than concepts from redox. Students seemed interested by the discussion of how changing pressures of O2 in venous vs arterial blood, could shift potentials further. I may incorporate this into the exercise in the future

Description: 

There are three ways to modulate the redox potential of a metalloenzyme:  Changing ligands, changing geometry, and changing solvent. When I introduce this topic in Bioinorganic, I try to give my students concrete examples of each.  I love this one because it applies what they learned in Gen Chem about the Nernst Equation to a biological problem.  Granted, I don't use a metalloenzyme as my example, but I do pull the biological chemistry into it at the end, by referrring to the cytochrome oxidase/O2 couple.  

In a Gen Chem class this could be used as an in class exercise or a (challenging) test question. 

Learning Goals: 

General Chemistry

  • A student should be able to balance a redox half-reaction in either acidic or basic conditions.
  • A student should know the conditions defined as standard conditions in aqueous electrochemical cells.
  • A student should understand the connection between the Nernst equation and potentials for reactions at other than standard conditions.
  • A student should be able to calculate the cell potential from two half-reaction potentials. 
  • A student should be able to explain the connection between redox potential and strength as an oxidizing (or reducing) agent.
  • A student should be able to calculate the free energy derived (or cost) from a given redox couple. 

 Advanced

  • A student should be able to relate these calculations to the affect of changing solvent (either pH, or concentrations of substrate or even availability of water in a microenvironment around the active site of a metalloenzyme) on the redox potential (and therefore the free energy of a biological redox couple).
Corequisites: 
Equipment needs: 

calculators

Prerequisites: 
Time Required: 
30 minutes, including discussion
29 Sep 2010

Cyclic voltammetry

Submitted by Chip Nataro, Lafayette College
Description: 

This is a short presentation on cyclic voltammetry. It is covers the basics and some simple electrode mechanisms. There is room for improvement (especially in my art) and suggestions are welcome.

Course Level: 
Prerequisites: 
Corequisites: 
Learning Goals: 

A student should be able to

1) describe the experimental set-up of a three electrode cyclic voltammetry experiment,

2) explain what information can be obtained from a cyclic voltammogram, and

3) describe simple electrode mechanisms.

Subdiscipline: 
26 May 2010

Battery in class activity

Submitted by Sheila Smith, University of Michigan- Dearborn
Evaluation Methods: 

Since this is an in-class activity, no assessment is typically performed because we go through the solutions during the class period. I have occasionally collected clicker results for some of the numerical questions to encourage students to really work at solving it on their own. The usefulness of the exercise can be measured in the quality of the discussion that is generated.

Description: 

This is an in-class exercise to be used at the end of General Chemistry (II).  I use it as a capstone exercise at the end of my second semester genchem course, but it would also make an excellent introductory review exercise at the beginning of a junior level inorganic course.  It provides an excellent review of topics from the entire semester (electrochemistry, acid-base, thermodynamics, colligative properties, solution chemistry and calculations) and shows how they are inter-related in a real world application (a car battery).

Learning Goals: 

• A student should be able to dissect the shorthand notation for a voltaic cell and convert that to a balanced redox equation in acidic conditions. • A student should be able to use the Nernst equation to calculate the potential of the battery at non standard conditions. • A student should be able to apply Hess' Law to calculate basic thermodynamic properties for a balanced equation. • A student should be able to calculate concentration of solutions, and to discuss the applicability of these different units. • A student should be able to use his/ her knowledge of colligative properties (both concept and calculation) to discuss the effect of temperature on a battery. • A student should be able to apply his/her knowledge of LeChatelier's Principle to make predictions about the effect changes in conditions will have on the state of a battery.

Corequisites: 
Prerequisites: 
Course Level: 
Equipment needs: 

none

Subdiscipline: 
Time Required: 
1 class period
6 May 2009

Henry Taube and Electron Transfer

Submitted by Bradley Wile, Ohio Northern University
Evaluation Results: 

Students seem to like the article. Many comment that Henry Taube has an extraordinary moustache!

Description: 

When teaching reactions and mechanisms of inorganic complexes, I tend to get to the end of the chapter (out of breath) and find myself thinking "*$#&, I forgot about electron transfer". While I think it is important that students get an understanding of this in an upper level inorganic course, I simply don't have, or forgot to budget the time to really talk about it.

I give them a brief rationale for why one would want to study mechanisms of electron transfer ("Remember all those redox reactions you balanced back in first year? Are you curious how those electrons moved around?"), and hand out/refer them to an excellently written retrospective on the career and research of Henry Taube (see link below).

I found this Inorganic Chemistry Viewpoint article to be very "readable", without sacrificing chemical detail (the nitty gritty). I breifly highlight some of the interesting points (Co3 + Cr2 --> Co2 + Cr3), and encourage them to read on to learn more about the career of a Nobel Prize winning inorganic chemist.

Topics Covered: 
Corequisites: 
Course Level: 
Learning Goals: 

Students should gain an understanding of the mechanisms for electron transfer. One of the other main goals for this reading is to have the students learn and appreciate the history of the field. I try to highlight the logical progression of research goals, and this article demonstrates the influence of Taube's early years on the research conducted later.

Subdiscipline: 
12 Jan 2009

House: Inorganic Chemistry

Submitted by Adam R. Johnson, Harvey Mudd College
Description: 

House (Inorganic chemistry):  The book is divided into 5 parts:  first, an introductory section on atomic structure, symmetry, and bonding; second, ionic bonding and solids; third, acids, bases and nonaqueous solvents; fourth, descriptive chemistry; and fifth, coordination chemistry.  The first three sections are short, 2-4 chapters each, while the descriptive section (five chapters) and coordination chemistry section (seven chapters covering ligand field theory, spectroscopy, synthesis and reaction chemistry, organometallics, and bioinorganic chemistry.) are longer.  Each chapter includes references (both texts and primary literature) for further reading, and a few problems (answers not available in the back of the book). 

I thought the text was generally good.  This text felt aimed at the introductory one-semester inorganic course offered at most schools rather than an advanced (senior/grad) course.  Although MO theory is developed in the text, most of the coordination chemistry is described using crystal field theory, though a short section on MO theory for complexes is included.  The sections on descriptive chemistry of the elements are very good and not overloaded with too much information, and the writing style (throughout the text) is easy to read and conversational.

My main complaint about the book, and this may seem petty, is that the molecular orbitals (throughout) do not accurately depict the way actual orbitals look;  they are too "pointy." 

The list price for the student text is $99.95 for a paperback, 864p version.

Prerequisites: 
Corequisites: 
Course Level: 
26 Mar 2008

Housecroft and Sharpe: Inorganic Chemistry, 3ed

Submitted by Lori Watson, Earlham College
Description: 

Housecroft and Sharpe (Inorganic Chemistry, 3ed): This is a comprehensive inorganic textbook designed primarily for students at the Junior/Senior level. P-Chem would not be needed as a prerequisite for this text, but would be helpful. It includes both theoretical and descriptive material along with special topics, enough for a two semester course though it is easily adaptable to a one-semester "advanced inorganic" course by choosing only some topics. It is written in a clear and generally readable style and the full-color graphic contribute to student understanding. Ancillaries include electronic versions of most figures, and a student site with a limited number of multiple choice review questions for each chapter. The 3rd edition updates the end-of -the-chapter problems, though disappointingly does not draw problems from the recent literature. In general, these are good review problems to make sure students understand the basic concepts, but some faculty will want to supplement student assignments with more challenging problems. The list price for the student text is $175 for a paperback, 1098p version.

Prerequisites: 
Corequisites: 
Course Level: 

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