appliccrtionf and cmalogief Competition Analogy Wayne L. Felty The Pennsylvania State University Wiikes-Barre Campus Lehman, PA 18627
In chemistry there are a number of phenomena that are the net result of competition between two chemical species. For examnle. the position of equilibrium in a BrdnstedLowry acid-base reaction depends upon the competition of tu.0 bases for the hydrogen ion; the equilibrium position and cell potential for a redox reaction depends upon the competition of two oxidizing agents for the electron(s); the polants of a covalent hond depends upon the competition between two atoms for shared electrons. These outcomes exhibit directionality (one participant dominates, or wins) as well as magnitude (depending on how different the two participants arej, facets which are also present in human sporting events. Let me illustrate using football competition as an analogy
This feature presents a collection of descriptive applications and analogies designed to help students understand some of lhe difficult concepts frequently encountered in chemistry. Contributions mat will prcduce e greafer appreciation and knowledge of political, religious, economic, historical. end scientific aspects of life are encouraged.
edited by: RON DELORENZO Middle Georgia College Cachran. Georgia 31014
for bond polarity-a comparison that my general chemistry students readily relate to. The magnitude of the polarity of a covalent hond is pronortional to the difference in electronezativitv of the two atoms forming the hond. The direction OFthe h&d moment is toward the element of ereater electroneeativitv. Consider ~ ~on the the 0 - F bond as a first example. ~ l u o r i n e i 4.0 Pauling scale) is more electronegative than oxygen (EN = 3.5). Hence, fluorine is negatively charged and oxygen is positively charged. The difference in electronegativity, AEN, is only 0.5, making the bond only moderately polar. Consider a second case, the 0 - H hond. Here, hydrogen (EN = 2.1) is less electronegative than oxygen, so that oxygen's polarity is now negative. The AEN of 1.4 makes this hond much more polar than the 0-F hond:
=
Fluorine is analogous to the top-ranked football team in the league (assuming that such rankings are an accurate ordering with respect t o ability). When playing the secondranked team (oxygen), there is stiff competition with little scoring because the two teams are rather closely matched. The top-ranked team eventually triumphs, hut by a slim margin, say, by a score of 7 to 3. Now consider the game between the same second-ranked team and the tenth-ranked team (hydrogen). Here, the no. 2 team really "looks good" and has little trouble running up a score of, say, 35 to 0. In football as in bonding, both the winner and the margin of victory depend a great deal on one's competitor!
Volume 62
Number 10
October 1985
869
