General Chemistry

9 Jun 2019

1FLO: PCET and Pourbaix

Submitted by Anne Bentley, Lewis & Clark College
Evaluation Methods: 

I graded each student’s problems as I would any other homework assignment, and they averaged about 80% on that part of the assignment. The other half of the total points for the assignment came from in-class participation.

Evaluation Results: 

We had a rich conversation about this article in class; it was probably one of the most interesting literature discussion conversations I’ve had. Although this was the only introduction to Pourbaix diagrams in the course, 12 of 15 students correctly interpreted a “standard” Pourbaix diagram on a course assessment.



This set of questions is based on a single figure from Rountree et al. Inorg. Chem. 2019, 58, 6647. In this article (“Decoding Proton-Coupled Electron Transfer with Potential-pKa Diagrams”), Jillian Dempsey’s group from the University of North Carolina examined the mechanism by which a nickel-containing catalyst brings about the reduction of H+ to form H2 in non-aqueous solvent. Figure 3 in the article presents an excellent introduction to the use of Pourbaix diagrams and cyclic voltammetry to determine the mechanism of a proton-coupled electron transfer reaction central to the production of hydrogen by a nickel-containing catalyst.

Course Level: 
Learning Goals: 

Students should be able to:

-  identify atoms in a multidentate ligand that can coordinate to a metal as a Lewis base

-  outline the difference between hydride addition to a metal and protonation of a ligand in terms of changes to the overall charge of the complex

-  analyze a Pourbaix diagram to predict the redox potential and pKa of a species

Implementation Notes: 

I have discussed the challenge of integrating literature discussions into my inorganic course in a BITeS post and the VIPEr forums. Each spring I try something a little different. This year I used three articles from the literature to frame our review of course material at the end of the semester, with each literature discussion occupying a one-hour class meeting.

In each case, the students completed problems before coming to class. While these problems were based on the journal articles, they did not require the students to read / consult the journal articles in order to complete the assignment. The students brought an electronic or paper copy of the article to class. I usually put students in groups (approximately 3 per group) and gave each group new questions to work on, which did draw from the article. After some time working in groups, each group presented their material to the rest of the class.

In implementing this particular literature discussion, I didn’t have any further questions for them.  I walked through some of the other figures from the article (especially Figure 1).  We discussed the authors’ use of color in creating Figure 3. We also reviewed the significance of horizontal vs vertical vs diagonal lines. Because I had not covered Pourbaix diagrams in the course, the activity was a good introduction to the concept.

Because these problems don’t require consultation with the article, they are suitable to use on an exam.

Time Required: 
8 Jun 2019

Crystallographic Resources at Otterbein University

Submitted by Kevin Hoke, Berry College

This site is another excellent resource from Dean Johnston (see also his Symmetry resource). It uses JSmol (in a web browser) to display different types of "Packing" and "Point Groups". For Packing, users can select different sizes for the atoms, display multiple unit cells, and rotate the model on the screen. Different layers can be color highlighted. 

Other portions of the website include resources for incorporating crystallography into the undergraduate curriculum.

Implementation Notes: 

I use the Packing Models as part of a homework assignment in which they are stepped through multiple models. The Packing models displayed are very straightforward to manipulate and I would not worrying about having first-year students interact with it. I have not used the Point groups portion yet, but I intend to share that with students who are learning symmetry.

As with some other JSmol-based models, atomic radii are used instead of ionic radii so the traditional color coding (yellow for sulfur, red for oxygen, gray for metal) will suggest for some models that the anions are smaller than cations. In my assignments, I have students evaluate how well that agrees with tables of ionic radii.

It can be used in any modern web browser that supports HTML5 and/or Java. I have accessed models successfully on my iPhone, though it is much easier to use on a larger screen.

8 Jun 2019

VIPEr Fellows 2019 Workshop Favorites

Submitted by Barbara Reisner, James Madison University

During our first fellows workshop, the first cohort of VIPEr fellows pulled together learning objects that they've used and liked or want to try the next time they teach their inorganic courses.

7 Jun 2019

Guideline for drawing chemical structures

Submitted by Bradley Wile, Ohio Northern University

This is the set of guidelines provided for authors by Nature Research. A 6-page PDF gives explicit guidance about rendering molecules using chemical drawing software, and a downloable ChemDraw template (.cds) is provided.

Related activities: 
Implementation Notes: 

I give this to all of my research students as part of the welcome to the group package.


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