structions in order to generate the Gran plot values. They then print out the plot with appropriate grid lines so that they can determine manually the end points from the plots. Finallv. ",for the last lab of the semester. the students determine the amount of calcium in maple syrup by atomic absorption. A standard addition analysis is used and students are again given explicit instructions on how to utilize Excel for this purpose. In this lab, they obtain a computer generated least squares fit in order to determine the concentration of calcium in the svruo. At this ooint in the semester, all students are ablcto perform these manipulations quite easily. The purpose of the computer section of these labs is to familiarize the students with the campus computer facilities and spreadsheets, thereby ensuring a minimum level of computer competence for future chemistry courses. These labs achieve this goal. We will be using these formats for the third time during the Fall of 1993. Copies of the detailed instructions are available upon request. Acknowledgment I would like to thank Dennis Baltuskonis, John Burke, Jean Floyd, William Kurtin, Nancy Mills, Kraig Steffen, and Frank Walmsley, each ofwhom has taught a t least one section of this laboratory during the two years this experiment has been included. Special thanks is extended to Nancy Mills for donating the 320 pennies. Literature Cited 1. Brenernan, G.L.:Parker, 0. J. J C h m Edur 19% 69,46647. 2. Schruartz,L. M.J C h m .Educ 1892.69.879-883, 3.Rasenthal,J. J C h .Educ. 1891.68, A%-,4286. 4. Riom, F J Chm.Ed=. 1991,68,A282-A283. 5.Van R M , H. J. Chrm Edur 1991,68,A28&A285. 6. Edwards, P A; McKey, J. B.J Cham.Educ 1885,69,648450. 7 . Vitz. E.J Chem Edue 1892.69.744449. 8. Riehardaon.T H.J. C h m .Edvc 1991,68,310311.
Use of a Spreadsheet in an Undergraduate Physical Chemistry Laboratory Sally O'Connor and Dechelle Bailey Xavier University of Louisiana New Orleans, LA 70125
This uauer illustrates the use of a commercial spreadskeet program to assist physical chemistry students in oroeessine their raw exwrimental data into meanineful computed cgemical or physical properties. The deveiopment of the uroerams has been influenced in Dart by our desire to make our students more computer [iterate but more importantly by the need to help them understand how raw experimental data are converted into chemical results in many modern instruments. In our increasin~lv technologica~world,the students are exposed more frequently to instrumentation that are computerized. Labo~atory~instructors realize more and more-the need to address what can be called "black box syndrome." For examule. students ean introduce a samule into an instrument:get printed results and have no idea what happened inside the instrument. By showing how a spreadsheet program can transform data, students are better able to understand what goes on inside the "black box." Presented .n pall at the 205tnMeel ng of the Amer can Chem~cal Soclety In the Dlv~s~on of Cnernlcal Education on Marcn 28,1993
Commercial spreadsheet programs such as LOTUS 1-2-3 and ASYST have been adapted for use in undergraduate laboratories (1-5).Our programs were developed on a PC computer using Microsoft Works, a multi-purpose software that allows our students to incorporate graphs directly into their word-processedlab report. Programs were develoued for six of the eight scheduled exueriments. two of which are described kelow. The impa& of the ;se of a soreadsheet in the Phvsical Chemistrv Lab a t Xavier Univ&sity is discussed. Bomb Calorimetry This experiment allows the student to determine the enthalpy of combustion of naphthalene from the rise in temperature of the water placed inside a Parr design bomb calorimeter (6).The program requires the student to input (1) the weights of the iron wire before p d aRer ignition, (2) the weight of the wire + pellet, and (3) the initial m d final temperatures of the water in the calorimeter.
The data obtained from the combustion of each pellet of either benzoic acid or naphthalene are entered. In our laboratory, we do one trial of benzoic acid and two trials of naphthalene. The spreadsheet then calculates the heat capacity of the calorimeter, the individual and average values of AU of combustion of naphthalene, and AH of combustion. Finallv. the uercentaee error of AH based on the published value'of enihalpy of-combustion of naphthaof the data lene is calculated. The student eets a orintout ' entered and the calculated reszts. Vapor Pressure of a Pure Liquid This experiment allows the student to determine the heat of vaporization of ethanol or water (7). The oromam requires the student to input applied pressures &d&eir corresponding boiling points. The spreadsheet uses these data to make a Clausius-Clapeymn plot of the l n p versus 1IT. A linear regression analysis of the data is performed, and the sloue. intercent and remession coefficient of the linear plot are report&. From tce slope and intercept, the enthalov and entroov of vauorization are calculated. The ~ t u d e n t " ~ eat s of ihitial data, calculated results, and a plot of his or her data. Programs for the other experiments were developed using the same approach. These include (a) the effect of temperature on %, experiment (8) to determine the enthalpy and entropy of dissociation ofbarium iodate, (b) the adiabatic expansion of gases (He and Coal experiment (7) to determine heat capacity ratios, (c) the bromination of acetone (8)to determine the reaction rate law, and (dl the conductance of electrolvtic solutions exueriment (8)to obtain the equilibriumco&tant for the dis$ociation of i weak acid. The uroerams eive a urintout of the raw data and Discussion In contrast to the non-traditional approach used in our general chemistry (9-10) and organic chemistry courses (11, 12), our physical chemistry courses a t Xavier are taught in a manner not unlike those taught a t major universities. A survey was given at the end of the Fall semester to the 36 students enrolled in the three sections of lab. Every respondent agreed that the use of spreadsheet benefited them. Some of the benefits commented on were (Continued on nertpoge)
Volume 71 Number 4 April 1994
A91
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