|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
1996
>
June
> |
|
Laboratory Experiments
|
|
|
|
Determination of Free-Energy Relationships Using Gas Chromatography
|
Nicholas H. Snow
Department of Chemistry, Seton Hall University, South Orange, NJ 07079
|
|
June 1996
Vol. 73 No. 6
p. 592
|
|
|
|
|
|
|
| Abstract |
|
By performing a few straightforward analyses on a gas chromatograph, it is possible to calculate the free energy, enthalpy, and entropy changes that occur when a compound transfers between the mobile and stationary phases. The partition theory of chromatography allows this transfer to be expressed as a chemical equlibrium. By calculating the equilibrium constant for this reaction from chromatographic retention
times, the standard free energy change may be determined, and from this, the standard enthalpy and entropy changes. Also, by calculating these values at several temperatures for structurally related compounds, it is possible to explore the relationship between chromatographic retention, standard free energy, and the structure of a compound. These calculations were performed for groups of homologous alcohols, acetates, and hydrocarbons on packed and capillary column gas chromatographs, using both polar and non-polar columns, and on computer simulation software. It is seen that for homologous compounds, the relationship between standard free energy change in partitioning and hydrocarbon chain length for this reaction is linear. It is also seen that gas chromatography represents a useful tool for the calculation and comparison of thermodynamic properties of compounds and that straightforward exercise of this type allows training of students in chromatographic analysis, basic partition theory, thermodynamic relationships, and linear free energy relationships.
|
|
| More Information |
 Citation |
Snow, Nicholas H. J. Chem. Educ. 1996 73 592.
|
Keywords |
|
History |
Created:
Last Updated: |
9/23/1999
5/22/2006
|
|
|
|
|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
1996
>
June
> Page
592
|
|
|
| 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.
|
| Contributions Welcome |
| JCE welcomes your submission |
| 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. |
| 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. |
|
