Here I have used Mathcad to solve a set of equiibrium chemistry equations which compute the various carbonate species as function of the partial pressure of carbon dioxide. Note the vast range of the solution values, approximately 10 orders of magnitude. I find this unique to chemistry problems.
Come on ! Any chemistry book points out that equilibruim coefficients, ion products, and solubility products are functions of temperature and ionic strength but then hastens to point out that for dilute solutions the activity is equal to the molar concentration, that is, the activity coefficient is essentially 1.0. The only time I have found it necessary to incorporate activity is with brine solutions from oil wells
I like the use of the symbolic solve for the carbonate ion, however that solution does not account for the charge balance equation nor the ion product of water which, I believe, would have to be solved simultaneously with the other equations, thus you would need to reduce 5 equations to 1. The carbonate inaccuracies are minimal I believe, about a 10% variation in concentrations that run around 10-7 moles per liter. You can't measure carbonate ion concentrations that accrately using standard techniques.
