JCE Online Journal of Chemical EducationDivision of Chemical Education, American Chemical SocietyAmerican Chemical Society
 | Subscriptions  | Software Orders  | Support  | Contributors  | Advertisers  | 

JCE Print
   Current Issue
 Previous Issues
 Supplements
 Search JCE Index

JCE Digital Library
   ChemInfo
 DigiDemos
 Featured Molecules
 LivTexts
 LrnCom
 QBank
 SymMath
 WebWare

JCE Software
   Latest Releases
 Software & Video
 Downloads
 Support

Only@JCE Online
   JCE Online Store
 JCE HS CLIC
 JCE Discussion Forums
   Biographical Snapshots
 ChemEd Resource Shelf
 Featured Molecules
 Hal's Picks
 Project Chemlab
 Reviewed WWW Sites
 "Web-Ed" Articles

About JCE
   Features
 Publications
 Operations
 Outreach
 Contact Us


  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > August  >
In the Laboratory
Weak Acid pKa Determination Using Capillary Zone Electrophoresis
Mike Solow
Department of Chemistry, City College of San Francisco, San Francisco, CA 94112
Cover
August 2006
Vol. 83 No. 8
p. 1194
Abstract
This article describes a general chemistry experiment designed to measure the pKa of benzoic acid using capillary zone electrophoresis. Despite the fact that modern biology relies so heavily on this analytical technique, students get very little explanation of the principles of electrophoresis in many biology labs. This laboratory exercise is intended to introduce undergraduate students to capillary electrophoresis while stressing the role of acid–base chemistry. While there are certainly easier ways to find the pKa of an acid (such as titration) this method requires only nanograms of the weak acid and is particularly well suited to analytes such as pharmaceuticals, herbicides, and pesticides that have low water solubility. In this experiment, students use capillary zone electrophoresis to determine the effective mobility of benzoic acid at two different hydrogen ion concentrations. A plot of these data yields the pKa of benzoic acid. Student results using this method (pKa = 4.23, RSD = 8.5%) are quite close to the literature value of 4.18.
Supplement
Instructions for the students including questions are available.
*  Contents JCE2006p1194W.doc (Microsoft Word)
*  Download
JCE2006p1194W.pdf

JCE2006p1194W.zip
More Information
*  Citation
 Solow, Mike. J. Chem. Educ. 2006 83 1194.
*  Keywords
 Acids / Bases; Analytical Chemistry; Aqueous Solution Chemistry; Carboxylic Acids; Electrophoresis; First-Year Undergraduate / General; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Instruction; Physical Chemistry
*  History
 Created:
Last Updated:		 6/21/2006
6/30/2006
<< Previous Article Table of Contents Next Article >>
  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > August  > Page 1194


Subscriptions
 Subscription Info
 Order Forms

JCE HS CLIC

Our Secondary School editors work hard to distill all the JCE materials to produce a fraction of particular interest to high school teachers. We call it CLIC.
 JCE HS CLIC

Contributions Welcome
JCE welcomes your submission
 Contributors' Corner

Advertisers
In recent years we have worked hard to better match our advertisers with our readers. When shopping for chemistry education materials, visit our advertisers' WWW sites first.
 Recent Advertisers

Be An Ambassador
Take JCE along on your outreach missions. Copies of the Journal, guest access to JCE Online, our publications catalog, and more are available for your participants.
 Outreach with JCE

Comments to
jceonline@chem.wisc.edu		 Copyright © Division of Chemical Education, Inc., American Chemical Society.
All rights reserved.