A. C. Norrir, S. E. Broadbent, ond N. R. Davies' Portsmouth Polytechn~c Portsmouth, Hampshire, England
A Computer Package for Physical
I
Chemistry Experiments
Many of the experiments used i n the physical chemistry laboratorv . ~ r o d u c eresults which are suitable for analvsis by computer. Computer analysis reduces the tedium associated with lengthy hand calculation and allows the treatment of the results t o be extended considerably. Also, a t Portsmouth, the early use of such programs by first-year students has proved highly successful a s a n informal preparation for lectures on computer appreciation and programming which are given in (he second year. Programs are available t o analyze d a t a from a comprehensive range of electrochemistry and kinetics experiments. Two further programs treat results from X-ray crystallographic and dielectric constant/dipole moment measurements. Where appropriate, d a t a are subjected to statistical analysis and, if a linear relationship exists between the important parameters, a least-squares procedure calculates the equation of the "best straight line" and estimates the standard deviations in the slope and intercept on the ordinate. Provided the standard deviation in t h e slope is less t h a n a preset amount, a correctly scaled and labelled graph is produced on the line-printer (or digital plotter). If the error is tea high t h e student must draw the graph for himself. The programs a n d t h e experiment options they cover are a s follows. &
Program ELECTRO Determination of the molar conductivity at infinite dilution of acetic acid. (b) Determination of the solubility of calcium and strontium fluoride from mnductivity measurements. (c) Determination of the molar conductivity at infinite dilution and the ionization constant of ehloroscetic acid bv Ostwald's dilution law. (d) ,~ Determination of thermodvnamic data from the tem~erature dependence clf the Pt 112 l i ~ AgCl l Ag cell. hlra-.orrmml t r f the mean actwlry cuetfxients of hydrwhlu. rlc at id using the PI H2 HC'I AgCl Ag~rll. (a)
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Where conductivity-concentration relationships are encountered far strong electrolytes, the molar conductivity at infinite dilution can be obtained either directly or by iterative calculation from the Debye-Hiickel-Onsager equation. In experiment (e), activity coefficients are derived from an extended version of the Debye-Hiickel limiting law.
Program KINETICS The program calculates rate constants for the following reaetions (a) The persulfate-iodide reaction. (b) The catalyzed decompositionof hydrogen peroxide. (c) The alkaline hydrolysis of ethyl acetate (followed by titrimetry or conductivity). (d) acid. . . The inversion of sucrose bv-hvdroehlorie . (e) The hydrolysis of methyl acetate catalyzed by hydrochloric and sulfuric acids. Option (e) also gives an estimate of the relative strengths of the catalyzing acids. Program 613 BT3 is used in a study of the effect of ion pair formation an the reaction between bromoacetate and thiosulfate ions in the presence of alkaline-earth cations. Details of this experiment are published e1sewhere.z
Program XRAY XRAY is written to determine the unit cell dimension of gold from an X-ray photograph produced by a gold wiie mounted in a Debye-Scherrer camera. The program can be used for data ohtained from any crystal with face-centred cubic symmetry. Program DIPOLE In normal operation, DIPOLE analyzes measurenients of the dielectric constant of eblorobenzene/cyclohexa~esolutions and calculates the dipole moment of cblorobenzene by the method of Halverstadt and Kumler.3 The program is also in regular use to calculate research results from any solute/solvent system.
A full description of the methods of calculation, program listings and sample print-outs together with a manual which describes t h e composition of the d a t a decks can be obtained from the authors. Two versions of each program are available, one written in ALGOL for the ICL 4130 machine, the other, without graph facilities, in Fortran IV. Department of Computer Science. 2Cosgrave, R. K., King. P. W., and Norris, A. C., J. CHEM. EDUC., 48,626 (1971). 3Halverstadt, I. F., and Kumler, W. D., J. Amer. Chem. Soe., 65,2988, (1942).
Volume 50, Number 7, July 1973
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