mnething new from the pwt Chemical Equilibrium In last month's column references were made t o "The How and Why of Chemical Reactions" (Leo Schubert., The Science Teacher. Januarv 1970. DD. 45-52) and t o "The Role of Kinetics i n ~ e a c h i n g1no;gaLic Chemistry," (Henry Tauhe J. CHEM. EDUC.. 191.451,. (September 1959)). It was stressed . 36 . t h a t articles such a s these heip those teachers who need updatinp, and just a s important, assist those chemistry teachers who are teaching o u t of their primary area. Whereas last month's articles dealt with "How fast do chemical reactions occur," This month's articles deal with, "To what extent d o they occur?" "Chemical Equilibrium," W e n d e l l H. S l a b a u g h , The S c i e n c e T e a c h e r , 61-66 ( N o v e m b e r 1967). "The concept of chemical equilibrium has long been recognized as one of the most important principles in chemistry." Slahaugh's initial statement cannot be averemuhasized. He starts his discussion citing simule or homoeeneous reactions familiar in most textbooks. he rquilibrimt nmstant, h',,, is shown derived from thr l.aw oi Mass Artlun. A good intrudurtog rrentment is given on ihr eftrets of such fnruri aj tcmp.ratLrr, prrsaure, cl,ncentralion uf rrnctnnLi, rarabLs. and inert materials.
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"The Carbonates, An Entertainment in Equilibrium," Daniel Luzon Morris, Chemistry, 47 [I], 6-9 (July-August 1974). Just as the title implies, this article gives the chemistry teacher easy access to ideas for helping to make the concept of equilibrium and its related principles interesting for presentation-d easy for students to learn. "Calcium carbonate (limestone) is generally regarded as an insoluble salt. . . If hydrochloric acid is added, the salt dissolves and a gas bubbles out. This gas, carbon dioxide, is an effective agent for demonstrating an intricate series of chemical reactions which illustrate the concept of dynamic equilihrium.Most of these reactions are well known and some have a curious histary-they were once used by traveling salesmen to sell magical elixirs to a gullihle public." !Activated Complex'-A Centenarian? A tribute to Leopold Pfaundler," E. W. Lund, J. CHEM. EDUC., 45, [2], 125, (February 1968). "When reading hundred-year-old papers one is surprised to learn what clear ideas some people had about general aspects of molecular phenomena in spite of a total lack of the detailed information we possess today." Lund begins his paper with a brief description of the status of kinetic theory in Pfaundler's time. He then describes Pfaundler's contribution to the field from a paper written in 1867. In describing the status of the kinetic theory, he writes of the work of Clausius who had presented a bold hypothesis. "The simplest and therefore most probable case of such a combination of atoms would be that two atoms form a molecule. This gives an explanation of the volume ratioa." Lund goes on to say, "It is surprising to learn that this idea was presented as a bold hypothesis by one of the mast outstanding scientists so long after Avogadro's contribution." The paper continues then with a description of Pfaundler's ideas on the nature of what more modern terminology would call the dynamics of equilihrium. Though Pfaundler did not use experimental evidence and used. . ."not a sinale mathematical formula (as Clausius did) . . . his ideas were of a real& physical character and he should certainly be reckoned as a pioneer in describing a chemical reaction between molecules as a dynamical event."
Edited by:
JOSEPH S. SCHMUCKLER Chairman of Science Education Temple University 345 RiUer Hall Philadelphia, PA 19122
CHEM KI). 1977 Waterloo Ontario Conference and at the CEC '78 ronlrrrnceat Heaver College. Glenvide \Philadelphial. Pa.
Julius Deroo, The Science Teacher, (January 1974), p. 44. Beryl G. Short, The Science Teacher, (May, 1976), p. 48. The reaction involves the use of rochelle salt and hvdroeen . - oeroa. ide, with rohalr(ll, eh.oride asa ratslyst. Short introauw%thr FI'IPCI of a limiting rengent hg using less hydrogen peroxidr initially than rallcd ior hy I)ercm. The rearthn . . . "mn he Fern quite el'fertirely by placing the reaction vessel on an overhead projector." "Passage of Fruit Flies through a Hole: A model for a Reversible Chemical Reaction," Elizabeth A. Runquist and Olaf Runquist, J. CHEM. EDUC., 49 [a], 534 (August 1972). Many models exist to teach the concept of systems in equilibrium. One of the more memorable ones, and still availahle,was used in the CHEM Study film, Equilibrium, narrated by Dr. George Pimentel. It involved a large fish aquarium consisting of two chambers connected by a glass tunnel with a "valve" that could he opened or closed. Goldfish served as the moving molecules! The Runquists, in their paper, described a similar model using a two chambered vessel and fruit flies (Drosophilla)as the moving molecules. The Runquist model shows that, "First-order" kinetics sre obeyed, and rate constants are reproducible. They state further that their "reaction" is temperature dependent (20°-219 C max). They describe the apparatus, its construction and use. Typical data are presented. For those of you interested in an "experiment" that integrates other sciences with chemistry, the last paragraph of the article should catch your attention. And finally-another macroscopic model of the sub-microscopic phenomenon, Equilihrium. "Equilibrium and T h e Dance Floor Problem," Don Baisley, C H E M 1 3 N E W S , p. 3, (January 1978). Baisley's suggestion and presentation can enliven the classroom teaching of the dynamics of chemical equilihrium with a most "reelvant" procedure.
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"Have Your Students Ever Seen a n Activated Complex?" Two references from the journal The Science Teacher discuss a reaction that is most useful. It was shown, among other places, at the 278
Journal of Chemical Education
This feature includes annotations of atticles from previous issues of the JOURN~L. and other science teaching journals. Topics will be presented in the issue prior to when the topic is taught in a typical high school cuniculum. Joseph 5. Schrnuckler is cunemly the chairman of the Depattment of Education and a Professor of Chemishy at Temple University. He was formerly a chemistry teacher a1 haverford Township Senlor rlgh Scnoo n Penns,fcana wnere he laught lor 15 years Or Scnml.crlsr rece re0 hlr BS oegree an 1952. MS aepree in 1954. and PhD n 1968 tom the Un .ersl, of Pennsylvan a n s nmerow awards ;n recognt on of nisomicatoon to teacnmg and &mm ~lucationinclde nls rece pt 0 1 t h ~Amencan Chem ca Soc ery James Bryant CoMnt A*wd m rllgn School Cnemlry Teach ng n 1968 Tnat year he amso ceca vsd the MCA and Chemm lndustr es Co.nc I a*aror He ,s one 01 me CPauthors to me Sllver Bwden Company program in chemlmy and was an algmal panc pant sna ConbibRor to me ChEM Study Program lor Hogn Scnool Cnem $try. ne has publlsned articles m ioblnals in sc en- and sclenca eaucauon.
