Just for fun, I did some research online about the pH value for chocolate. You probably know about the scale, but if not: it has 14 points. If something has a low number, it's an acid; if it has a high number, it's a base (a.k.a. alkaline). The number 7 is considered "neutral".
The pH for natural cocoa powder generally ranges from 5.0 to 5.8, so it's slightly acidic. And the pH for alkalized cocoa powder is 6.2 to 6.8, so it's even less acidic, practically neutral. And chocolate cake, for what it's worth, is 7.2 to 7.6.
HOWEVER, that's not the only thing to go by. I also discovered something called the "ash factor." When food is burned/metabolized by the body, its pH can change internally. For example, oranges are very acidic foods when you eat them, but they become alkaline afterwards. Weird, eh?
CHOCOLATE, on the other hand, apparently becomes quite acidic after you eat it. The website below explains this, and also offers a BIG and interesting list on which foods turn which way during digestion.
Hmmm... now I understand why, if I eat too much chocolate, my acid reflux often acts up and I get heartburn. :(