Real problems

We have now completed our survey of the thermodynamic principles required to model natural systems. It only remains to gain practice in formulating problems involving natural systems in thermodynamic terms. Quite often, that is the hardest part. Once the problem is set up in terms of relevant reactions and components, the equations can be solved by anyone who has absorbed the previous chapters. However, choosing the appropriate components and setting up the relevant balanced reactions only comes from experience. In this chapter we explore a few situations that have been investigated by thermodynamic methods.

Is the sea saturated with calcium carbonate?

If you have ever been to Florida or the Bahamas, you may be aware that there are vast areas adjacent to the coasts where the sea bottom at shallow levels is a white mud, which turns out to be made of almost pure aragonite. Carbonate muds extend well out to the deep sea as well; in fact, a fairly large proportion of the sea bottom is composed of calcium carbonate. There are also countless calcitic atolls and reefs throughout the tropical zones of the world. Given this amount of contact between the sea and calcium carbonate, both calcite and aragonite, plus the fact that there are vigorous oceanic currents stirring things up constantly, plus the fact that things have not changed drastically for millions of years, you would think that there would be little doubt that the system consisting of the oceans plus their bottom sediments must have reached equilibrium by now.