lntractive Computer Programs for Equilibrium and Kinetics A set of interactive computer program has been written for use by undergraduates with no knowledge of computers. I n response to specific prompting, the student describes s. chemical system to the program, which calculates the equilibrium state or time development of the system. The student may then change some parameters of the system and immediately observe its response. I n this way, the programs provide responsive computer models of chemical systems, whose behavior students may compare with experiment, theory, or manual calculation. The programs are designed for use in a time-sharing environment, but may be used in a conventional mode as well. They are written ASA Standard Basic Fortran, which is acceptable to most large and small computers. The documentation for each program, including a. program listing, operating instructions, assignment, explanatory text, and programming notes, sre available from the author. The program EQUIL is a fast and efficient program for solving general ionic and gas-phase equilibrium problems. I t has been applied to polyprotic acid titrations, complex formation, and solubility calculations. I t requires the student to enter all equilibrium and mass balance equations, and to make order of magnitude guesses a t a few equilibrium concentrations. GIBBS solves equilibrium problem by minimizing free energy, treating temperature, pressure and multiple phases explicitly. I t has been applied to gas phase equilibria, liquid-liquid distributions, and gas-solid equilibria. Its results are calculated with the same absolute accuracy far each species. Similar problems are solved in program BALAN, by balancing the free energy of reactants and products in each reaction. It calculates its results with the same relative zccuracy for each species. RATES solves general kinetics problem using a fourth-order Runge-Kutta dgorithm with varying step size. I t has been applied to many simple reactions, and to steady state snd clock reactions where sharply changing concentrations pose difficulties for simpler algorithm. WALTERB. NEILSEN HARVARD UNIVERSITY M ~ s s ~ c n u s ~02138 rrs CAMBRIDGE,
414 / Journal o f Chemical Education
