My Notes
Categories
This LibreTexts module by Dr. Tom Neils and Dr. Stephanie Schaertel provides a clear and thorough explanation of why some biochemistry and organic chemistry textbooks get the pKa of water wrong. The pKa of water at 25 ºC is 14.0 and not 15.7. This module describes the derivation of the correct value and describes why the value of 15.7 should not be used.
Students will be able to explain how to derive the correct value for the pKa of water.
This resource not only corrects a common error found in some textbooks, but it also provides a great example of how science knowledge is created and how difficult it can be to correct.
Evaluation
Not only could this be used to teach about pKa's and activities, but it could also be used to help students explore the nature of scientific knowledge. We like to believe that science is self-correcting, but is it?
I have not used this in teaching yet and don't have any evaluation results.
Jan 2023: The pKa of water saga continues. The editor-in-chief of JACS agreed to do an ACS video about it with the folks who have been working to correct the wrong value. It's quite interesting! It's on the ACS Youtube website: https://www.youtube.com/watch?v=u5Nyzs3CSc8
Tom, Stephanie, and their colleague Todd Silverstein expanded on these ideas in a lovely Helvetica Chimica Acta paper: https://doi.org/10.1002/hlca.202400103.