Well that's an interesting question, in reality any genre can be educational. The great thing about games that are educational is simply you can make learning fun, while some games forget this and decide that since it's an educational game it has to "BEAT THE INFORMATION INTO YOUR MIND WITH A BASEBALL BAT" and thus stops being fun and becomes little more than a visual textbook. There have been several example of games that have remembered this though, many RTS or RPG have been through history, RPG and puzzles have done chemistry, anything with well typed text has done language. Most of these have done it in such a gentle manner that it didn't feel like being beat in the back of the head with the information hammer. Really any genre can be used to make an educational game, and most commercial games these days are educational (to the extent that idiots refuse to notice it (no offense to anyone who never noticed)), it just depends on how you go about it, I would say that it would probably be best not to do chemistry as the main point in the game as then it would be "information hammer bashing you in the back of the head", instead add it as a side feature that would be useful to progressing the game, for example upgrading weapons or armor, mixing "potions", or something along the lines of that. Also rather than having only one subject towards education there, perhaps mixing a multitude of subjects perhaps history, chemistry, and mythology.
A few things to remember when doing a educational game:
1. Don't bash information in quickly, this makes games boring and then it quickly becomes tedious just to play.
2. Instead of making the subject being taught the primary point push it to the side and wrap it around the primary concept.
3. Be gentle when teaching, we're gamers our minds are delicate give it to us in small doses or let us figure things out in the game on our own.
4. Possibly mix multiple subjects into the background of the game, use some of them to work out a story line while putting others as a side feature or minigame.
5. Give part of the information, if it truly interests us we will seek more on it from other sources (Final Fantasy VII, Sephiroth is a good example of this(Yes, Sephiroth is educational))
If you can do 3 out of 5 of those things you'll have a successful game that is educational and fun to play.
~TheCrym