Chapter 5: Equilibrium, Part 1 - An Introduction to Equilibrium and Acid-Base Chemistry
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An Introduction to Equilibrium and Acid-Base Chemistry
Figure 5-1: Water is not merely an inert medium into which other species dissolve, but a reactive compound in its own right. Photo: By Tiago Fioreze - CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6111892
We chemists, I’m afraid to say, are a hopelessly aquocentric bunch. It’s not simply driven by a romanticism inspired by the beauty of the ocean, although we appreciate that as much as anyone. Our preoccupation with water is professional in nature. Specifically, we give water a privileged position over other compounds. For example, we prefer to use a temperature scale (Celsius) that is defined by melting and boiling points of water. One of our most commonly used units of energy is the calorie, defined as the energy required to raise one gram of water one degree Celsius. And even that unit - the gram - is defined as the mass of one milliliter of water.
This apparent fixation on water is understandable, even among non-chemists. Three-quarters of our planet’s surface is covered with the stuff (Figure 5-1); we need large quantities of it every day to survive, we gestate in it, and all terrestrial forms of life trace their evolutionary roots back to it. Life began in it and no known example of life can survive without it. As such, it is often not considered to be a “chemical” (although Monsanto used it under its systematic name, dihydrogen monoxide, in an advertising campaign many years ago along with the phrase “Without chemicals, life itself would be impossible.”) But a chemical it is, and behave as a chemical it does. Like other chemicals it can react to form new species and its repertoire of available reaction pathways, as we will see, is surprisingly large for such a simple molecule. It is, in fact, intimately tied to the biochemistry of life, not just as a passive medium in which other reactions take place, but as an active participant in thousands of different transformations.