Submitted by Patrick Holland / Yale University on Mon, 07/28/2008 - 10:24
My Notes
Topics Covered

This is an interactive Challenge in which students have to find others in the room with whom they "match" as a hard or soft acid or base. It brings to life the way inorganic chemists think about HSAB. Inorganic Challenges are exercises designed to be solved by a small group of students. Some Challenges practice a problem-solving algorithm, some reinforce important concepts, and some involve creativity or games. You can pick and choose Challenges from our Web site to increase active learning in your classroom, and we ask that you contribute creative Challenges of your own to give a head start to teachers at other colleges and universities! Please visit

Attachment Size
acidbase1.pdf 27.9 KB
Implementation Notes

At the end, I ask a few students to introduce to the class their acid or base, and what they found.

Time Required
30 minutes


Evaluation Results

Works ok. It's a little silly, but fun.

Creative Commons License
Attribution, Non-Commercial, Share Alike CC BY-NC-SA
Sheri Lense / University of Wisconsin Oshkosh

I used a variation of this activity in teaching HSAB theory.  I began by giving a lecture on HSAB theory, during which I asked students to look for trends and come up with explanations for the classification of acids and bases as hard or soft. Each student was then assigned an acid or base, and the class formed their acid-base reactions.  Following this activity, they worked in groups on a worksheet to use HSAB to predict whether acid-base reactions would be favorable or unfavorable, and apply HSAB to the design of chelating agents to remove metals from the body.   Overall, this activity was a lot of fun, and students did very well on both midterm and final questions in which they were asked to use HSAB theory to predict the favorability of acid-base reactions, predict how ambidentate ligands such as thiocyanate would coordinate to various metals, and design chelating agents for various metals.

Wed, 12/18/2013 - 15:08 Permalink
Rachael Kipp / Suffolk University

I used this activity right before Valentine's day.  I would agree with the statement of it being a little silly, but fun.  My students got very competitive.  Almost every student in the class received full credit on the HSAB-based questions on the homework assigment they completed after this actviity.

Thu, 02/20/2014 - 12:52 Permalink