JCE Software, 8B1: REACT

REACT: Exploring Practical Thermodynamic and Equilibrium Calculations

Richard W. Ramette
Carleton College, Northfield, MN 55057

Note:
Series B (MS DOS) software previously included on the General Chemistry Collection CD-ROM is now available for free download by Journal of Chemical Education subscribers.
Go to the download page.

REACT facilitates three chemistry manipulations that often are exasperating, and sometimes seem impossible to introductory chemistry students. They are:

Balancing equations having unusual or complicated stoichiometry,
Looking up standard thermodynamic data for all reactants and products and calculating the changes in free energy, enthalpy and entropy for the reaction,
Performing calculations, given an initial set of concentrations and pressures, to find the equilibrium conditions.
REACT uses a database of standard thermodynamic properties for 570 substances. Most of the enthalpies and free energies of formation, and the absolute entropies, are taken from the NBS tables of chemical thermodynamic properties.
REACT's interface makes it easy to search the database either by name or by formula. Thermodynamic data and molar mass are displayed for each selected species. The user chooses reactants and products to build up a skeleton equation. REACT balances the equation and shows its thermodynamic properties and equilibrium constant, or standard potential for a half-reaction. The user can enter different temperatures and see the change in properties.

If desired, one can enter initial concentrations or pressures for species other than pure solids or liquids. REACT calculates equilibrium values taking account of activity coefficients for aqueous ions. The calculation may be repeated for various temperatures.
For half-reactions, the calculation option is to enter concentrations and pressures for the species in a half-cell. The Nernstian potential is calculated at the chosen temperature.

Perhaps the best way to use REACT is to answer practical chemical questions. Problems that are quite intimidating to solve by hand are made easy by REACT. Below are four examples of the type of problems your students can solve with REACT.

You are a research environmentalist, and you want to predict the concentration of oxygen in a cold mountain stream at 5°C.

You have a bottle of 0.1 M acetic acid on your lab desk. It seems stable, but does thermodynamics predict an eventual decomposition into graphite and water?

What is the balanced equation for this reaction (1)?

H⁺ + [Cr(NH₂CONH₂)₆]₄[Cr(CN)₆]₃ + MnO₄^- --->
Cr₂O₇^2- + CO₂(g) + NO₃^- + Mn²⁺+ H₂O(l)

Here's a scary thought for you to explore. Consider any body of fresh water, such as your local river or the Great Lakes, constantly exposed to the nitrogen and oxygen of Earth's atmosphere. You can write a balanced equation for the hypothetical reaction:

N₂(g) + O₂(g) + H₂O(l) ---> H⁺ +NO₃^-
Does thermodynamics predict that this reaction is spontaneous, whereby our lakes will be partially converted to nitric acid? It doesn't seem to happen: a bottle of pure water exposed to air doesn't gradually become more acidic. But this inhibition is really a matter of kinetics, not thermodynamics. Apparently there is at least one large activation energy barrier to be overcome, so the reaction rate is infinitesimal.
Now for the scary part: conceivably an industrial pollutant may one day enter Earth's water and act as a catalyst for this reaction, allowing it to reach equilibrium quickly. You are called in as a consultant to make a realistic prediction of what concentration the nitric acid would reach at equilibrium assuming only one small northern lake (in winter, at 0°C) is infected with the catalyst. Assume that the air composition (21% oxygen, 78% nitrogen) remains constant.
Because REACT deals with such questions so quickly, and because users can set up equations so easily, the program can serve students as an enjoyable learning tool for thermodynamic and equilibrium questions.
Hardware and Software Requirements
Programs in Series B of JCE: Software require an IBM PC-compatible microcomputers with 640K RAM, one disk drive, and a VGA or compatible graphics adapter. PC- or MS-DOS version 3.1 or later is also required.
REACT supports a Microsoft compatible mouse; a mouse is recommended but not required.
REACT requires 350 K of free disk space for installation onto a hard disk drive
Literature Cited

Reaction courtesy of John Camp, a Texas High School teacher.

First Published: April 1995
Citation: Ramette, R. W. . REACT: Exploring Practical Thermodynamic and Equilibrium Calculations J. Chem. Educ. Software 8B1
Keywords: Lecture Aid; Computer Room; Laboratory; Simulation; Instructor; High School; General; Physical; Balancing equations; DH, DS, DG calculations

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JCE Online | Journal | Software | Internet | Happenings | About JCE | Contact JCE

Last Updated: April 26, 2001
Created: December 3, 1996 Created by: J. L. Holmes
Comments to: jceonline@chem.wisc.edu

© 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved.



REACT: Exploring Practical Thermodynamic and Equilibrium Calculations
Richard W. Ramette Carleton College, Northfield, MN 55057

Note:	Series B (MS DOS) software previously included on the General Chemistry Collection CD-ROM is now available for free download by Journal of Chemical Education subscribers. Go to the download page.

REACT facilitates three chemistry manipulations that often are exasperating, and sometimes seem impossible to introductory chemistry students. They are: Balancing equations having unusual or complicated stoichiometry, Looking up standard thermodynamic data for all reactants and products and calculating the changes in free energy, enthalpy and entropy for the reaction, Performing calculations, given an initial set of concentrations and pressures, to find the equilibrium conditions. REACT uses a database of standard thermodynamic properties for 570 substances. Most of the enthalpies and free energies of formation, and the absolute entropies, are taken from the NBS tables of chemical thermodynamic properties. REACT's interface makes it easy to search the database either by name or by formula. Thermodynamic data and molar mass are displayed for each selected species. The user chooses reactants and products to build up a skeleton equation. REACT balances the equation and shows its thermodynamic properties and equilibrium constant, or standard potential for a half-reaction. The user can enter different temperatures and see the change in properties. If desired, one can enter initial concentrations or pressures for species other than pure solids or liquids. REACT calculates equilibrium values taking account of activity coefficients for aqueous ions. The calculation may be repeated for various temperatures. For half-reactions, the calculation option is to enter concentrations and pressures for the species in a half-cell. The Nernstian potential is calculated at the chosen temperature. Perhaps the best way to use REACT is to answer practical chemical questions. Problems that are quite intimidating to solve by hand are made easy by REACT. Below are four examples of the type of problems your students can solve with REACT. You are a research environmentalist, and you want to predict the concentration of oxygen in a cold mountain stream at 5°C. You have a bottle of 0.1 M acetic acid on your lab desk. It seems stable, but does thermodynamics predict an eventual decomposition into graphite and water? What is the balanced equation for this reaction (1)? H⁺ + [Cr(NH₂CONH₂)₆]₄[Cr(CN)₆]₃ + MnO₄^- ---> Cr₂O₇^2- + CO₂(g) + NO₃^- + Mn²⁺+ H₂O(l) Here's a scary thought for you to explore. Consider any body of fresh water, such as your local river or the Great Lakes, constantly exposed to the nitrogen and oxygen of Earth's atmosphere. You can write a balanced equation for the hypothetical reaction: N₂(g) + O₂(g) + H₂O(l) ---> H⁺ +NO₃^- Does thermodynamics predict that this reaction is spontaneous, whereby our lakes will be partially converted to nitric acid? It doesn't seem to happen: a bottle of pure water exposed to air doesn't gradually become more acidic. But this inhibition is really a matter of kinetics, not thermodynamics. Apparently there is at least one large activation energy barrier to be overcome, so the reaction rate is infinitesimal. Now for the scary part: conceivably an industrial pollutant may one day enter Earth's water and act as a catalyst for this reaction, allowing it to reach equilibrium quickly. You are called in as a consultant to make a realistic prediction of what concentration the nitric acid would reach at equilibrium assuming only one small northern lake (in winter, at 0°C) is infected with the catalyst. Assume that the air composition (21% oxygen, 78% nitrogen) remains constant. Because REACT deals with such questions so quickly, and because users can set up equations so easily, the program can serve students as an enjoyable learning tool for thermodynamic and equilibrium questions. Hardware and Software Requirements Programs in Series B of JCE: Software require an IBM PC-compatible microcomputers with 640K RAM, one disk drive, and a VGA or compatible graphics adapter. PC- or MS-DOS version 3.1 or later is also required. REACT supports a Microsoft compatible mouse; a mouse is recommended but not required. REACT requires 350 K of free disk space for installation onto a hard disk drive Literature Cited Reaction courtesy of John Camp, a Texas High School teacher.


News \| Issues \| CD-ROM / Video \| Find It! \| Technical Support \| For Authors
JCE Online \| Journal \| Software \| Internet \| Happenings \| About JCE \| Contact JCE

Last Updated: April 26, 2001 Created: December 3, 1996	Created by: J. L. Holmes Comments to: jceonline@chem.wisc.edu

© 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved.