what chemical do i need to remove rust stains from my driveway?

Personally I never let that bother me, but I would get a heavy duty detergent and a heavy duty scrub brush and clean it as best as you can. If stain persists, spray it with Rustoleum High Heat Black paint. Let the driveway heat up first and paint will stick better. Rule of thumb, if you can't get rid of it, HIDE IT! Case in point, I have dark siding that faded but is uneven and blotchy. I experimented and found that Armorall was just the thing. I sprayed Armorall on the siding and wiped it to make it even and it looks like new and will last about a year. There is always a solution but as they say, you need to think outside the box.

Most any rust remover chemical which are mostly acids will get rust off but so will the rain. Ignore it and it will be gone in a few weeks.

Try putting vinegar or lemon juice on the stain.