massaction

A python package for the numerical solution of mass-action laws with constraints for the description of chemical reactions.

Installation

The easiest way to install massaction is from PyPi using pip.

pip install massaction

Usage

The major perk of massaction is the simple syntax in which one can set up the description of a chemical equilibrium. For instance, the mass-action law for the oxyhydrogen reaction may be set up in just a few lines of Python code:

from massaction.model import ChemModel

mymodel = ChemModel(3) # set up a model with 3 chemical species
h2o, h2, o2 = mymodel.get_all_species() # give names to the species objects

# first set up the reaction equation, then define constraints to ensure atom balance
reaction = h2 + o2 >> 2*h2o
ln_equilibrium_constant = 20. # arbitrary units
constraint_hydrogen = 2*h2 + 2*h2o == 1.0 # arbitrary units
constraint_oxygen = h2o + 2*o2 == 10.0 # arbitrary units

# now solve the system of equations to obtain an array with the natural logarithm of the concentrations
ln_concentrations = mymodel.solve( [reaction], [ln_equilibrium_constant], [constraint_hydrogen, constraint_oxygen] )

The resulting array ln_concentrations is array([ -0.69314718, -22.94443898, 1.55814462]), which contains the entries $\ln\left(c(\mathrm{H_2O})\right)$, $\ln\left(c(\mathrm{H_2})\right)$, and $\ln\left(c(\mathrm{O_2})\right)$, respectively.