|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
1998
>
September
> |
|
In the Laboratory
|
|
|
|
The Reaction of a Food Colorant with Sodium Hypochlorite: A Student-Designed Kinetics Experiment
|
Josefina Arce, Rosa Betancourt, Yamil Rivera, and Joan Pijem
University of Puerto Rico, Rio Piedras Campus, Department of Chemistry, P. O. Box 23346, San Juan, Puerto Rico 00931-3346
|
|
September 1998
Vol. 75 No. 9
p. 1142
|
|
|
|
|
|
|
| Abstract |
|
The kinetics of the reaction of the food colorant FD&C Blue #1 with sodium hypochlorite (Clorox) is described in a student-designed experimental format. In this format, students are guided- by means of questions- to make decisions regarding concentration of reagents, choice of equipment, and actual laboratory procedures to be followed. This format provides an opportunity for students to apply the concepts and skills learned in class and in previous laboratory sessions to a new problem. We have found that this experience helps students gain depth of understanding of all concepts involved. The reaction (with a large excess of NaOCl) is followed with a Spectronic 20 at the Blue #1 colorant lmax of 630 nm. The %T is measured over time and three graphs: A vs time, ln A vs time and 1/A vs time are plotted to find that the second one is linear and thus first order with respect to the Blue #1. When the concentration of NaOCl is reduced to one-half the original value, it is found that the rate is reduced by one-half, indicating that the reaction is first order with respect to NaOCl and second order overall. The rate constant of the reaction is determined from the slope of the curve and the mean obtained by our students is 17 M-1 min-1 at room temperature (about 28° C).
|
|
| More Information |
 Citation |
Arce, Josefina; Betancourt-Perez, Rosa; Rivera, Yamil; Pijem, Joan. J. Chem. Educ. 1998 75 1142.
|
Keywords |
introductory, high school chem, laboratory instruction, kinetics, uv-vis spectroscopy
|
History |
Created:
Last Updated: |
June 21, 1999
June 23, 2005
|
|
|
|
|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
1998
>
September
> Page
1142
|
|
|
| Chemistry Teacher Connection |
|
The "Chemistry Teacher Connection" (CTC) is especially for high school chemistry teachers. For only $40/year, it offers an online-only subscription to CLIC along with membership in the Division of Chemical Education, normally $65/year. CTC subscribers receive access to all articles and supplements from 1996 through the current issue.
|
| C&EN CLICs |
|
Through special arrangement with the ACS, JCE High School CLIC is now able to provide subscribers with online access to Chemical & Engineering News articles that have been selected specifically for secondary science instructors and their students.
|
JCE Collections Available
|
Occasionally, collections of JCE back issues become available for donation to individual teachers, schools, or libraries. JCE matches collections with interested recipients. Recipients pay shipping costs or pick up the collection.
|
| Contributions Welcome |
| JCE welcomes your submission |
| Fishing for New Ideas |
 Always in the
process of
improving, CLIC
welcomes ideas and comments.
Email Us |
|
