Wavelength Deterrnlnations To the Editor:
To Count or Not To Count All Grades To the Editor:
I t was reassurine for me to learn that others are also troubled with the &oblems of (1) dropping the lowest test grade and (2) utilizing laboratory grades [1987,64,517].The first of these two problems still plagues me, and my solution 1. The curve shown in Figure 5 implies a simple relationship befor it continues to evolve tween wavelength, A, and position. Although this is true for gratHowever, I have used and then abandoned Dinsmore's ing spectrographs (1)it is not true for the Hilger and Watts D187, approach of discarding the lowest grade and countina the which contains a Pellin-Broca prism for the dispersing element. next-to-the-lowest twice for- the following reason: For prism instruments it is the wavenumber, i, i.e., the reciprocal Each quarter I have one or more A-students who decide to of the wavelength, which is very nearly linear with the pasition slack offjuat before their last test. Thesestudents then enter (2). It is, therefore, possihle to fit the calibration data more the final examination with pseudo-A averages, i.e., they are conveniently, either graphically or analytically,to an equation of familiar with onlv 7540%of the work. As such.. thev. usuallv the f o m i = f (position) rather than A = f (position). For a physical chemistry experiment, it would not be unreasonahle for a l ~ perform o poohy on the final exam. At this point, whether students to fit the calibration data using a nonlinear regression I give these students A's or their mathematically desewed procedure. Alternatively, the wavelengths could be determined grade (usually H'sor C's), I suffersome mental anguish when using the Hartman dispersion formula (3)which also implies that thesestudentsclaim that thev lost their Aaverare becauseof the use of i = f (position) rather than A = f (position) is more the final exam. I have therefbre gone full circleand am now conventional among spectroscopists. counting all examination grades. 2. Rappon and Greer designate the C2Swan bands as A311,-X311.. Unlike my approach to the first problem, I stiU use my (Note that each pi should have heen capitalized.)The use of X to original solution t o the second problem, although I am a label the 311, state implies that thean. state is the ground state of minority of one in my department: I simply ignore lahoratoCI and further implies that the lowest energy electron configuraIt has been known since 1963(4) that the tion is KK og2s,2r,3~a'. ry grades of B or better when calculating final grades. For stab lies 716.2 cm-' above the actual ground state, correctly laboratory grades of C or lower, penalties of -5, -10, and designated as XIZ+,. This state arises from the KK r72~7~~n,~ -15 points are added t o student averages. configuration which is the lowest energy electron configuration for Cz. Thus the correct, i.e., currently accepted, designation for Ronald DeLorenzo the Swan bands should be d3n, a3n. (5). Middle Oewgia College 3. Recently, I have had occasion to look at the 4-6 band of the Swan Cochran. GA 31014 system using the cone of an acetylene-oxygen torch for the light source and a 24-ft Ebert spectrograph in 10th order. The exposure time was approximately 15min. Since the acetylene-oxygen torch is such a bright source, it should be possible to use it to obtain a color film spectrum in a reasonable time using Rappon To the Editoc and Greer's experimental system. While I do believe that no consistently poor work merits John L. Deutsch any forgiveness, the plan I have proposed errs very little in State University College of Am 8 Sciences that direction; moreover, its most notable feature is the Genesao. NY 14454 encouraeement t h a t i t offers for continual good study effort. That oftkn is not the case when all tests count. When every Llterature Cited test counts, one bad stumble takes a student out of the race. I. Sayer, R. A.ExprrimntalSeclmaeapy, 3rd 4.; Dover: New York, 1963: p 248 2. Ref I, p 7.45. H e sees his A or B as definitely gone and from then on his 3. Ref I, p 240. effort is often a diminished one, below his best ability. With 4. BaUik,E.A.:Ramaay,D.A.Aatmphya. J. 1963,137,61. 5. Huber, K. P.:Huzbug, G. Molecular Spectra and Molecular Sfruelure IV; Van mv nolicv one stumble still leaves him in the race, and every Nostrand Reinhold: New York, 1 9 7 % 112. ~ effort is made t o avoid a second fall; so good studicontinues. I don't w o r n about the few with a string of A's letting up Grade lnflatlon much. ~ h e ~ k n othat w the final exam will cover everything To the Editor: and that they need to learn i t all.
In resnonse to the useful article, "Atomic and Molecular spectra'using Polaroid Films" by Rappen and Greer 11987, 64,4531,I would like to offer the following comments:
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In his article, "Using Sequencing Questions in Chemistry Examinations" 11987, 64, 5321, Hemmerlin states that the grading system he has developed "is perceived as more fair bv the student" than the "all or nothing" smtem. No wondkr. A simple probability calculation shows that a student who knows nothing a t a l C o r a random-number generator-is most likely to earn a score of 50%! Although the questions under discussion are seemingly of a multiplechoice type with 24 answers, because of the partial-credit treatment, they are, in fact, as "benign" as the True-False type. It used t o he t h a t a perfectly valid statistical correction was annlied t o multinle-choice auestions. Unfortunatelv, most &ulties have g k e n u p thisbractice, with the conk: quence that "grade inflation" begins a t the exam stage, and the impression is created that students are learning more than thev actuallv are: as a result thev learn less than they should.
Journal of Chemical Education
Flwida Soluthern College Lakeland. FL 33802
For or Against Le ChYelier? To the Editor:
I t does seem a pity that in your June 1988 issue that contained on p 482 a most cogent statement of the reasons whywe should never again mention the (non-)principleof Le Chatelier, you give that very subject a n honorable mention on p 558! Can i t be that the left and right hands operate under separate control? The next time you hear a mention of Le Chatelier, I hope that you think of how unnecessary and unprincipled i t is.
George Vogel
S. R. Logan
BDStOn College
University of Ulster Coleraine, N. Ireland BT52 ISA
Chesmut Hill. MA 02167
360
Howard L. Dinsrnore
