Well if you really worry about it then what you can do now is go to his office and let him get to know you better(the ochem professor). Just kinda talk to him whenever you have the chance and talk about your experiences in his class,etc. If you can't do that, i say you should still apply anyway. LOR is not that critical if you ask me. With a good stats even generic LOR won't hurt you.
The impact that letter has depends heavily on whether you are getting a committee letter. If you are having a committee letter put together whoever does it draws on everything you present them and may include one or more of the letters you submit to them. Point being It would just add more usable (and positive) information. Even if you submti letters directly i would still go ahead and send it. As long as other recommenders can write a personal letter it will only help.
I also was in a similar situation and received a LOR from a professor I never met. I sent him a photo, my personal statement, resume and lab experience so that he could draft a more informed recommendation.
I read a horror story somewhere of some a**hole prof who wrote a letter for a student who did well in his course but they didn't really know each other. The LOR went something like this.
_____ asked me to write a letter of recommendation for dental school and here it is.
Sincerely
**shole prof
I'm sure this is an extreme case, but make sure that the prof agrees to write a GOOD LOR, not just a LOR.
