Chemistry classes, in my experience, often require you to do lots of simple calculations. This isn't the sort of thing you should be focusing on! Do you know the mass of 12.8 mol of methane? With Chemboy, you can find out easily enough just by typing "12.8 mol C H4". The answer is 205.34732 g.
If you run Windows, grab the zip file. It should run just fine.
Programmers can get it via asdf-install, or directly from chemboy-latest.tar.gz. You can also download the PGP Signature.
Once you have it installed, type "(chemboy-text:chemboy-repl)" at the REPL, and you'll get a text-based interface. Try typing "help" at the prompt, and away you go!
There are a few subcomponents that ought to be useful on their own. These files should be portable ANSI Common Lisp. They've been tested on SBCL and LispWorks without any problems. If you have any problems with them, please tell us on the chemboy-devel mailing list.
An essential part of any general chemistry program is the periodic table of the elements. Nobody wants to copy the whole thing by hand, and figuring out how to represent it can be a minor headache. Therefore, you should download the peridic-table package.
You can get the latest version via asdf-install or directly from periodic-table-latest.tar.gz. You can also download the PGP Signature.
It can sometimes be useful to be able to parse chemical compounds in a user-friendly syntax into easy-to-manipulate s-expressions. You also want to be able to go in reverse. You could probably write your own parser---or you could just install the chemical-compounds package.
You can get the latest version via asdf-install or directly from chemical-compounds-latest.tar.gz. You can also download the PGP Signature.